IMPROVING COTTON PRODUCTIVITY BY PLANT ...prr.hec.gov.pk/jspui/bitstream/123456789/8035/1/Ali...2018/11/01 · Ali Zohaib 2007-ag-2489 ii To The Controller of Examinations, University

IMPROVING COTTON PRODUCTIVITY BY PLANT GROWTH

RETARDANT AND BORON APPLICATION

By

ALI ZOHAIB

M.Sc. (Hons.) Agriculture (Agronomy)

2007-ag-2489

A thesis submitted in partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

I N

A G R O N O M Y

DEPARTMENT OF AGRONOMY,

FACULTY OF AGRICULTURE,

UNIVERSITY OF AGRICULTURE,

FAISALABAD, PAKISTAN

2017

i

Declaration

I hereby declare that the contents of the thesis, “Improving cotton productivity by

plant growth retardant and boron application” are product of my own research and no part

has been copied from any published source (except the references, standard mathematical

and genetic models/equations/formulae/protocols etc.). I further declare that this work has

not been submitted for award of any other diploma/degree. The university may take action

if the information provided is found inaccurate at any stage. (In case of any default the

scholar will be proceeded against as per HEC plagiarism policy).

Ali Zohaib

2007-ag-2489

ii

To

The Controller of Examinations,

University of Agriculture,

Faisalabad.

We, the supervisory committee certify that the contents and form of the thesis

submitted by Ali Zohaib, Regd. No. 2007-ag-2489 have been found satisfactory and

recommend that it be processed for evaluation by the External Examiner(s) for the award

of degree.

Supervisory Committee

Chairman --------------------------------------------

(Dr. Abdul Jabbar)

Member ---------------------------------------------

(Dr. Riaz Ahmad)

Member ---------------------------------------------

(Dr. Shahzad Maqsood Ahmed Basra)

iii

Dedicated To

My Respected

MY LOVING PARENTS, MY CARING WIFE

TAHIRA TABASSUM, MY ELDER BROTHER

WAQAS AHMED AND MY KIND TEACHER DR.

ABDUL JABBAR

WHO ALWAYS SUPPORTED AND HELPED ME TO

CATCH MY GOALS AND SEE ME SHINING LIKE A SUN

iv

A C K N O W L E D G E M E N T

First of all, I would like to thank the grace of Allah Almighty for completing this

work at this final shape. All respects are for the Holy prophet Muhammad (Peace be upon

him and his family), for enlightening our conscience with the essence of faith in Allah, and

for giving us the golden principles of Islam.

I owe a great depth of gratitude and appreciation for my ex-supervisor Dr.

Ehsanullah (Late), Professor, Department of Agronomy, University of Agriculture,

Faisalabad for his sympathetic attitude, step to step guidance and unwavering support

during my academic and research endeavors.

My deepest affection and gratitude to my supervisor, Dr. Abdul Jabbar for his

supervision and for choosing of this research, his scientific guidance, generosity, providing

the possible laboratory materials and support during the period of the research.

My deepest and warm gratitude to advisory committee: Dr. Riaz Ahmad,

Chairman and Professor, Department of Agronomy, University of Agriculture, Faisalabad

and Dr. Shahzad Maqsood Ahmed Basra, Professor, Department of Agronomy,

University of Agriculture, Faisalabad. I am thankful for the guidance they provided me

during my work and evaluation of the work I did.

I am also highly appreciative to Higher Education Commission (HEC),

Government of Pakistan for granting me Indigenous Ph.D. fellowship during my doctoral

study. I really appreciate such fellowships as it is source of hope for students of Pakistan

who want to do something for their homeland.

Special gratefulness and appreciation to my colleagues and friends for assistance

and advices provided during my work. Last but not least, I would like to offer my special

thanks to my family especially my mother and wife whose utmost efforts, endless support,

love and prayers enabled me to complete this work and without their support and kindness

I wouldn't have been able to achieve this work and I cannot find any word to express my

sincere appreciation and gratitude to them.

(Ali Zohaib)

v

TABLE OF CONTENTS

Sr. No. Title Page No.

DECLARATION i

DEDICATION iii

ACKNOWLEDGEMENT iv

TABLE OF CONTENTS v

LIST OF TABLES xi

LIST OF FIGURES xlvii

LIST OF APPENDICES xlix

LIST OF ABBREVIATIONS l

ABSTRACT 1

1 INTRODUCTION 2

2 REVIEW OF LITERATURE 8

2.1. Boron 8

2.1.1. Factors affecting boron availability in soil 8

2.1.2. Boron in plant physiology and biochemistry 10

2.1.3. Effect of boron deficiency on cotton 11

2.1.4. Augmenting boron nutrition and nutrient use efficiency 12

2.2. Plant growth regulators 12

2.2.1. Plant growth retardant 13

2.2.1.1. Plant growth and architecture 14

2.2.1.2. Dry matter production and partitioning 15

2.2.1.3. Nutrient dynamics and use efficiency 15

2.2.1.4. Earliness 16

2.2.1.5. Yield and related attributes 17

2.2.1.6. Fiber quality 18

2.2.1.7. Cotton seed quality 19

2.3. Boron application methods 19

2.3.1. Soil application 20

2.3.2. Foliar application 21

2.4. Planting density 21

2.4.1. Plant growth and canopy structure 22

2.4.2. Dry matter production, partitioning and crop growth rate 22

2.4.3. Earliness 23

2.4.4. Yield and related attributes 24

2.4.5. Fiber and cottonseed quality 24

2.5. Management of high planting density 25

2.6. Conclusion 26

3 MATERIALS AND METHODS 27

3.1. General 27

3.1.1. Site 27

3.1.2. Experimental material 27

vi

3.1.3. Soil 27

3.1.4. Meteorological data 28

3.1.5. Experimental treatments and design 28

3.2. Experiment 1: Influence of foliar applied mepiquat chloride

and boron on growth, productivity and earliness of cotton at

different planting densities

28

3.3. Experiment 2: Influence of foliar application of mepiquat

chloride and soil applied boron on growth, productivity and

earliness of cotton

29

3.4. Crop husbandry 35

3.4.1. Seedbed preparation 35

3.4.2. Sowing 35

3.4.3. Fertilization 35

3.4.4. Irrigation 35

3.4.5. Plant protection measures 35

3.4.6. Picking 36

3.5. Procedures for recording data 36

3.5.1. Agronomic attributes of cotton 36

3.5.1.1. Plant height (cm) 36

3.5.1.2. Number of main stem nodes per plant 36

3.5.1.3. Internodes length (cm) 36

3.5.1.4. Number of monopodial branches 36

3.5.1.5. Number of sympodial branches per plant 36

3.5.1.6. Node for first effective boll bearing (sympodial) branch 37

3.5.1.7. Number of nodes above white flower (NAWF) 37

3.5.1.8. Number of nodes above last cracked boll (NACB) 37

3.5.2. Phenological development of cotton 37

3.5.2.1. Number of days to first squaring (days) 37

3.5.2.2. Number of days to first flowering (days) 37

3.5.2.3. Number of days to first boll opening (days) 37

3.5.2.4. Boll maturation period (days) 37

3.5.2.5. Mean maturity days (days) 37

3.5.2.6. Earliness index (%) 38

3.5.2.7. Production rate index (kg ha-1 day-1) 38

3.5.2.8. Thermal time 38

3.5.3. Allometric attributes of cotton 38

3.5.3.1. Leaf area (cm2) 38

3.5.3.2. Dry matter production and its distribution (g plant-1) 39

3.5.3.3. Total dry matter (g plant-1) 39

3.5.3.4. Reproductive-vegetative dry matter ratio 39

3.5.3.5. Leaf area index 39

3.5.3.6. Leaf area duration (days) 39

vii

3.5.3.7. Crop growth rate (g m-2 day-1) 39

3.5.3.8. Net assimilation rate (g m-2 day-1) 40

3.5.4. Boll distribution pattern of cotton 40

3.5.4.1. Proportion of bolls at first position (%) 40

3.5.4.2. Proportion of bolls at second position (%) 40

3.5.4.3. Proportion of bolls at outer position (%) 40

3.5.5. Yield and related attributes of cotton 40

3.5.5.1. Plant population 40

3.5.5.2. Number of unopened bolls per plant 41

3.5.5.3. Number of opened bolls per plant 41

3.5.5.4 Boll density 41

3.5.5.5. Total number of bolls per plant 41

3.5.5.6. Boll weight (g) 41

3.5.5.7. Number of seeds per boll 41

3.5.5.8. Seed index (g) 41

3.5.5.9. Seed cotton yield (kg ha-1) 41

3.5.5.10. Lint yield (kg ha-1) 41

3.5.5.11. Cotton seed yield (kg ha-1) 41

3.5.6. Fiber quality attributes of Cotton 42

3.5.6.1. Ginning out turn (%) 42

3.5.6.2. Fiber length (mm) 42

3.5.6.3. Micronaire (µg inch-1) 42

3.5.6.4. Fiber strength (g tex-1) 42

3.5.6.5. Fiber uniformity ratio (%) 42

3.5.6.6. Fiber maturity (%) 43

3.5.7. Plant analysis 43

3.5.7.1. Photosynthetic pigments of cotton (mg g-1) 43

3.5.7.2. Tissue nutrient contents of cotton 43

3.5.7.2.1. Sampling and sample preparation 43

3.5.7.2.2. Nitrogen (mg g-1 DW) 43

3.5.7.2.3. Phosphorus (mg g-1 DW) 44

3.5.7.2.4. Potassium (mg g-1 DW) 45

3.5.7.2.5. Boron (µg g-1 DW) 46

3.5.7.2.6. Zinc (µg g-1 DW) 46

3.5.7.2.7. Manganese (µg g-1 DW) 47

3.5.7.2.8. Iron (µg g-1 DW) 47

3.5.7.3. Seed protein content (%) 47

3.5.7.4. Seed protein yield (kg ha-1) 47

3.5.7.5. Seed oil content (%) 48

5.7.6. Seed oil yield (kg ha-1) 48

3.5.7.7. Seed ash content (%) 48

3.5.8. Nutrient use efficiency 48

viii

3.5.9. Critical concentration of boron 49

3.5.10. Boron fertilizer requirement of cotton 49

3.6. Soil bioassay: Influence of previously treated cotton crop with

mepiquat chloride and boron on emergence and seedling

growth of progeny

49

3.7. Procedures for data recording 49

3.7.1. Emergence 49

3.7.1.1. Final emergence percentage (%) 49

3.7.1.2. Emergence index 49

3.7.1.3. Mean emergence time (days) 50

3.7.2. Seedling growth 50

3.7.2.1. Root length of seedling (cm) 50

3.7.2.2. Shoot length of seedling (cm) 50

3.7.2.3. Root fresh weight (mg) 50

3.7.2.4. Shoot fresh weight (mg) 50

3.7.2.5. Root dry weight (mg) 50

3.7.2.6. Shoot dry weight (mg) 50

3.7.2.7. Seedling vigor index 50

3.8. Economic analysis 51

3.9. Statistical analysis 51

4 RESULTS AND DISCUSSION 52

4.1. Influence of foliar applied mepiquat chloride and boron at

different planting densities

52

4.1.1. Plant growth and architecture 52

4.1.2. Discussion 63

4.1.3. Phenological development 64

4.1.3.1. Calendar time 64



4.1.5. Allometric attributes 82

4.1.5.1. Dry matter accumulation 82

4.1.5.1.1. Vegetative dry matter 82

4.1.5.1.2. Reproductive dry matter 87

4.1.5.1.3. Total dry matter 91

4.1.5.1.4. Reproductive-vegetative dry matter ratio 91

4.1.5.2. Crop growth rate 96

4.1.5.3. Leaf area and leaf area index 97

4.1.5.4. Leaf area duration 97

4.1.5.5. Net assimilation rate 108


4.1.7. Boll distribution pattern 111


ix



4.1.11. Fiber quality attributes 134


4.1.13. Photosynthetic pigments 140


4.1.15. Tissue nutrient contents 148

4.1.15.1. Macronutrients 148

4.1.15.2. Micronutrients 156


4.1.17. Cotton seed nutritional quality 170



4.1.20. Critical value of boron 178

4.1.21. Boron fertilizer requirement 178


4.1.23. Soil bioassay 183

4.1.23.1. Emergence and seedling growth of progeny seedlings 183

4.1.23.2. Biomass accumulation in progeny seedlings 190


4.1.25. Regression and correlation analysis 200

4.1.26. Economic analysis 203

4.2. Effect of foliar applied mepiquat chloride and soil applied

boron on cotton

206

4.2.1. Plant growth and architecture 206


4.2.3. Phenological development 213

4.2.3.1. Calendar time 213



4.2.5. Allometric attributes 225

4.2.5.1. Dry matter accumulation 225

4.2.5.1.1. Vegetative dry matter 225

4.2.5.1.2. Reproductive dry matter 228

4.2.5.1.3. Total dry matter 228

4.2.5.1.4. Reproductive-vegetative dry matter ratio 233

4.2.5.2. Crop growth rate 233

4.2.5.3. Leaf area and leaf area index 233

4.2.5.4. Leaf area duration 240

4.2.5.5. Net assimilation rate 240


4.2.7. Boll distribution pattern 243

x




4.2.11. Fiber quality attributes 255


4.2.13. Photosynthetic pigments 260


4.2.15. Tissue nutrient contents 265

4.2.15.1. Macronutrients 265

4.2.15.2. Micronutrients 265


4.2.17. Cotton seed nutritional quality 277



4.2.20. Critical value of boron 281

4.2.21. Boron fertilizer requirement 282


4.2.23. Soil bioassay 286

4.2.23.1. Emergence and seedling growth of progeny 286

4.2.23.2. Biomass accumulation in progeny seedlings 290


4.2.25. Regression and correlation analysis 295

4.2.26. Economic analysis 297

5 SUMMARY 300

CONCLUSION 311

FUTURE RESEARCH THRUSTS 312

LITERATURE CITED 313

xi

LIST OF TABLES

Table No. Title Page No.

3.1 Soil physico-chemical properties for experiment 1 30

3.2 Soil physico-chemical properties for experiment 2 31

4.1 Analysis of variance for influence of foliar applied mepiquat

chloride and boron at various planting densities on agronomic

attributes of cotton (2014)

54


chloride and boron at various planting densities on agronomic


54

4.3a Influence of foliar applied mepiquat chloride and boron at

various planting densities on plant height (cm) of cotton (2014)

55

4.3b Influence of foliar applied mepiquat chloride and boron at


55



55



55


various planting densities on number of main stem nodes of

cotton (2014)

56



cotton (2014)

56



cotton (2015)

56



cotton (2015)

56


various planting densities on internodes length (cm) of cotton

(2014)

57



(2014)

57



(2015)

57



(2015)

57

xii


various planting densities on number of monopodial branches

of cotton (2014)

58



of cotton (2014)

58



of cotton (2015)

58



of cotton (2015)

58


various planting densities on number of sympodial branches of

cotton (2014)

59



cotton (2014)

59



cotton (2015)

59



cotton (2015)

59


various planting densities on node for first effective boll

bearing (sympodial) branch of cotton (2014)

60




60




60




60


various planting densities on nodes above white flower

(NAWF) of cotton (2014)

61




61

xiii




61




61


various planting densities on nodes above cracked boll

(NACB) of cotton (2014)

62




62




62




62


chloride and boron at various planting densities on phenology

of cotton (2014)

66


chloride and boron at various planting densities on phenology

of cotton (2015)

66

4.21 Influence of foliar applied mepiquat chloride and boron on

days to squaring initiation (days) of cotton at various planting

densities (2014)

67

4.22 Influence of foliar applied mepiquat chloride and boron at

various planting densities on days to squaring initiation (days)

of cotton (2015)

67


various planting densities on days to flowering initiation (days)

of cotton (2014)

67



of cotton (2014)

67



of cotton (2015)

68


various planting densities on days to flower initiation (days) of

cotton (2015)

68

xiv


various planting densities on days to boll opening initiation

(days) of cotton (2014)

68




68




69




69


various planting densities on boll maturation period (days) of

cotton (2014)

69


various planting densities on boll maturation period (days) of

cotton (2015)

69


various planting densities on mean maturity days of cotton

(2014)

70



(2014)

70



(2015)

70



(2015)

70


various planting densities on earliness index (%) of cotton

(2014)

71



(2014)

71



(2015)

71



(2015)

71

xv


various planting densities on production rate index (kg ha-1

day-1) of cotton (2014)

72


various planting densities on production rate index (kg ha-1

day-1) of cotton (2014)

72


various planting densities on production rate index (kg ha-1 day-

1) of cotton (2015)

72


various planting densities on production rate index (kg ha-1 day-

1) of cotton (2015)

72


chloride and boron at various planting densities on thermal

time of cotton (2014)

75


chloride and boron at various planting densities on thermal

time of cotton (2015)

75


thermal time (GDD) taken from sowing to squaring initiation

of cotton at various planting densities (2014)

76

4.38

Influence of foliar applied mepiquat chloride and boron on

thermal time (GDD) taken from sowing to squaring initiation


76

4.39a Influence of foliar applied mepiquat chloride and boron on

thermal time (GDD) taken from sowing to flowering initiation


76

4.39b Influence of foliar applied mepiquat chloride and boron on



76




77




77


thermal time (GDD) taken from squaring to flowering

initiation of cotton at various planting densities (2014)

77




77

xvi




78


thermal time (GDD) taken from sowing to boll opening


78




78




78




79


thermal time (GDD) taken from flowering to boll opening


79


thermal time (GDD) taken from flowering to boll opening


79


chloride and boron at various planting densities on allometric


83




83


various planting densities on vegetative dry matter (g m-2) of

cotton (2014)

84



cotton (2014)

84



cotton (2015)

84



cotton (2015)

84


various planting densities on reproductive dry matter (g m-2) of

cotton (2014)

88

xvii



cotton (2014)

88



cotton (2015)

88



cotton (2015)

88


various planting densities on total dry matter (g m-2) of cotton

(2014)

92



(2015)

92


various planting densities on reproductive-vegetative dry

matter ratio of cotton (2014)

95




95




95




95




98




98


various planting densities on mean crop growth rate (g m-2 d-1)

of cotton (2014)

99


various planting densities on mean crop growth rate (g m-2 d-1)

of cotton (2015)

99


various planting densities on leaf area index of cotton (2014)

102



102

xviii



102



102


various planting densities on leaf area duration (days) of cotton

(2014)

107



(2014)

107



(2015)

107



(2015)

107


various planting densities on mean net assimilation rate (g m-2

d-1) of cotton (2014)

109


various planting densities on mean net assimilation rate (g m-2

d-1) of cotton (2015)

109


chloride and boron at various planting densities on boll

distribution pattern at sympodial branches of cotton (2014)

113


chloride and boron at various planting densities on boll

distribution pattern at sympodial branches of cotton (2015)

113


various planting densities on percent of first position bolls (%)

of cotton (2014)

114


various planting densities on percent of first position bolls (%)

of cotton (2015)

114


various planting densities on percent of second position bolls

(%) of cotton (2014)

114




114




115

xix




115


various planting densities on percent of outer position bolls (%)

of cotton (2014)

115



of cotton (2014)

115



of cotton (2015)

116



of cotton (2015)

116


chloride and boron at various planting densities on yield related


119


chloride and boron at various planting densities on yield related


119


various planting densities on number of plants m-2 of cotton

(2014)

119


various planting densities on number of plants m-2 of cotton

(2015)

119


various planting densities on number of opened bolls per plant

of cotton (2014)

120



of cotton (2014)

120



of cotton (2015)

120



of cotton (2015)

120


various planting densities on number of opened bolls per m-2

of cotton (2014)

121

xx



of cotton (2014)

121



of cotton (2015)

121



of cotton (2015)

121


various planting densities on number of unopened bolls per

plant of cotton (2014)

122




122




122


various planting densities on total number of bolls per plant of

cotton (2014)

122



cotton (2014)

123



cotton (2015)

123



cotton (2015)

123


various planting densities on average boll weight (g) of cotton

(2014)

123



(2014)

124



(2015)

124



(2015)

124

xxi


chloride and boron at various planting densities on yield and

related attributes cotton (2014)

127


chloride and boron at various planting densities on yield and

related attributes of cotton (2015)

127


various planting densities on number of seeds per boll of cotton

(2014)

128



(2014)

128



(2015)

128



(2015)

128


various planting densities on seed index (g) of cotton (2014)

129



129



129



129


various planting densities on seed cotton yield (kg ha-1) (2014)

130



130



130



130


various planting densities on lint yield (kg ha -1) of cotton

(2014)

131



(2014)

131


various planting densities on lint yield (kg ha-1) of cotton

(2015)

131

xxii



(2015)

131


various planting densities on cotton seed yield (kg ha-1) (2014)

132



132



132



132


chloride and boron at various planting densities on fiber quality

of cotton (2014)

136


chloride and boron at various planting densities on fiber quality

of cotton (2015)

136


various planting densities on ginning out turn (%) of cotton

(2014)

137


various planting densities on ginning out turn (%) of cotton

(2015)

137


various planting densities on fiber length (mm) of cotton

(2014)

137


various planting densities on fiber length (mm) of cotton

(2015)

137


various planting densities on micronaire (µg inch-1) of cotton

(2014)

138


various planting densities on micronaire (µg inch-1) of cotton

(2015)

138


various planting densities on fiber (g tex-1) strength of cotton

(2014)

138


various planting densities on fiber (g tex-1) strength of cotton

(2015)

138

xxiii


various planting densities on fiber uniformity ratio (%) of

cotton (2014)

139


various planting densities on fiber uniformity ratio (%) of

cotton (2015)

139


various planting densities on fiber maturity (%) of cotton

(2014)

139


various planting densities on fiber maturity (%) of cotton

(2015)

139


chloride and boron at various planting densities on

photosynthetic pigments of cotton (2014)

142


chloride and boron at various planting densities on

photosynthetic pigments of cotton (2015)

142


various planting densities on chlorophyll a content (mg g-1) of

cotton (2014)

143



cotton (2014)

143



cotton (2015)

143



cotton (2015)

143


various planting densities on chlorophyll b content (mg g-1) of

cotton (2014)

144



cotton (2014)

144



cotton (2015)

144



cotton (2015)

144

xxiv


various planting densities on total chlorophyll content (mg g-1)

of cotton (2014)

145



of cotton (2014)

145



of cotton (2015)

145



of cotton (2015)

145


various planting densities on chlorophyll a/b ratio of cotton

(2014)

146



(2015)

146



(2015)

146


various planting densities on carotenoids content (mg g-1) of

cotton (2014)

146



cotton (2014)

147



cotton (2015)

147



cotton (2015)

147


chloride and boron at various planting densities on contents of

macronutrients in leaves and seed tissues of cotton (2014)

149




149


various planting densities on leaf nitrogen content (mg g-1 DW)

of cotton (2014)

150

xxv



of cotton (2014)

150



of cotton (2015)

150



of cotton (2015)

150


various planting densities on seed nitrogen content (mg g-1

DW) of cotton (2014)

151




151




151




151


various planting densities on leaf phosphorus content (mg g-1


152




152




152




152


various planting densities on seed phosphorus content (mg g-1


153




153




153

xxvi




153


various planting densities on leaf potassium content (mg g-1


154




154




154




154


various planting densities on seed potassium content (mg g-1


155




155




155




155



micronutrients in leaves and seed tissues of cotton (2014)

158




158


various planting densities on leaf boron content (µg g-1 DW) of

cotton (2014)

159



cotton (2014)

159



cotton (2015)

159

xxvii



cotton (2015)

159

4.144c Influence of foliar applied mepiquat chloride and boron at


cotton (2015)

160


various planting densities on seed boron content (µg g-1 DW)

of cotton (2014)

160



of cotton (2014)

160



of cotton (2015)

160



of cotton (2015)

161

4.146c Influence of foliar applied mepiquat chloride and boron at


of cotton (2015)

161


various planting densities on leaf zinc content (µg g-1 DW) of

cotton (2014)

161



cotton (2014)

161



cotton (2015)

162



cotton (2015)

162


various planting densities on seed zinc content (µg g-1 DW) of

cotton (2014)

162



cotton (2014)

162



cotton (2015)

163

xxviii



cotton (2015)

163


various planting densities on leaf manganese content (µg g-1


163




163




164




164


various planting densities on seed manganese content (µg g-1


164




164




165




165


various planting densities on leaf iron content (µg g-1 DW) of

cotton (2014)

165



cotton (2015)

165



cotton (2015)

166


various planting densities on seed iron content (µg g-1 DW) of

cotton (2014)

166



cotton (2014)

166

xxix



cotton (2015)

166



cotton (2015)

167


chloride and boron at various planting densities on cotton seed

nutritional quality (2014)

171


chloride and boron at various planting densities on cotton seed


171


various planting densities on cotton seed oil content (%) (2014)

172



172



172



172


various planting densities on cotton seed protein content (%)

(2014)

173



(2014)

173



(2015)

173



(2015)

173


various planting densities on cotton seed ash content (%)

(2014)

174



(2014)

174



(2015)

174

xxx



(2015)

174


various planting densities on cotton seed oil yield (kg ha-1)

(2014)

175



(2014)

175



(2015)

175



(2015)

175


various planting densities on cotton seed protein yield (kg ha-

1) (2014)

176



1) (2014)

176



1) (2015)

176



1) (2015)

176

4.171 Analysis of variance for maternal induced changes in

emergence and seedling growth of cotton progeny in response

to foliar applied mepiquat chloride and boron at various

planting densities (2015)

184



to foliar applied mepiquat chloride and boron at various


184

4.173a Maternal induced changes in final emergence percentage (%)

of cotton progeny in response to foliar applied mepiquat

chloride and boron at various planting densities (2015)

185

4.173b Maternal induced changes in final emergence percentage (%)



185

xxxi

4.174a Maternal induced changes in final emergence percentage (%)



185

4.174b Maternal induced changes in final emergence percentage (%)



185

4.175 Maternal induced changes in mean emergence time (days) of

cotton progeny in response to foliar applied mepiquat chloride

and boron at various planting densities (2015)

186



and boron at various planting densities (2016)

186

4.177a Maternal induced changes in emergence index of cotton

progeny in response to foliar applied mepiquat chloride and

boron at various planting densities (2015)

186

4.177b Maternal induced changes in emergence index of cotton



186

4.178a Maternal induced changes in emergence index of cotton



187

4.178b Maternal induced changes in emergence index of cotton



187

4.179a Maternal induced changes in root length (cm) of cotton



187

4.179b Maternal induced changes in root length (cm) of cotton



187

4.180a Maternal induced changes in root length (cm) of cotton



188

4.180b Maternal induced changes in root length (cm) of cotton



188

4.181a Maternal induced changes in shoot length (cm) of cotton



188

4.181b Maternal induced changes in shoot length (cm) of cotton



188

xxxii

4.182a Maternal induced changes in shoot length (cm) of cotton



189

4.182b Maternal induced changes in shoot length (cm) of cotton



189

4.183 Analysis of variance for maternal induced changes in seedling

growth of cotton progeny in response to foliar applied

mepiquat chloride and boron at various planting densities

(2015)

192



mepiquat chloride and boron at various planting densities

(2016)

192

4.185a Maternal induced changes in root fresh weight (mg) of cotton



193

4.185b Maternal induced changes in root fresh weight (mg) of cotton



193

4.186a Maternal induced changes in root fresh weight (mg) of cotton



193

4.186b Maternal induced changes in root fresh weight (mg) of cotton



193

4.187a Maternal induced changes in shoot fresh weight (mg) of cotton



194

4.187b Maternal induced changes in shoot fresh weight (mg) of cotton



194

4.188a Maternal induced changes in shoot fresh weight (mg) of cotton



194

4.188b Maternal induced changes in shoot fresh weight (mg) of cotton



194

4.189a Maternal induced changes in root dry weight (mg) of cotton



195

xxxiii

4.189b Maternal induced changes in root dry weight (mg) of cotton



195

4.190a Maternal induced changes in root dry weight (mg) of cotton



195

4.190b Maternal induced changes in root dry weight (mg) of cotton



195

4.191a Maternal induced changes in shoot dry weight (mg) of cotton



196

4.191b Maternal induced changes in shoot dry weight (mg) of cotton



196

4.192a Maternal induced changes in shoot dry weight (mg) of cotton



196

4.192b Maternal induced changes in shoot dry weight (mg) of cotton



196

4.193 Maternal induced changes in root/shoot ratio of cotton progeny

in response to foliar applied mepiquat chloride and boron at

various planting densities (2015)

197


in response to foliar applied mepiquat chloride and boron at

various planting densities (2016)

197

4.195a Maternal induced changes in seedling vigour index of cotton



197

4.195b Maternal induced changes in seedling vigour index of cotton



197

4.196a Maternal induced changes in seedling vigour index of cotton



198

4.196b Maternal induced changes in seedling vigour index of cotton



198

4.197 Table 4.197: Coefficients of determination (R2) and correlation

coefficients (r) denoting goodness of fit and association

strength between different variables (2014)

201

xxxiv

4.198 Coefficients of determination (R2) and correlation coefficients

(r) denoting goodness of fit and association strength between

different variables (2015)

202

4.199 Economic analysis 204

4.200 Marginal analysis 205

4.201 Analysis of variance for influence of foliar application of

mepiquat chloride and soil applied boron on agronomic


207


mepiquat chloride and soil applied boron on agronomic


207

4.203 Influence of foliar application of mepiquat chloride and soil

applied boron on plant height (cm) of cotton (2014)

208


applied boron on plant height (cm) of cotton (2015)

208


applied boron on number of main stem nodes of cotton (2014)

208


applied boron on number of main stem nodes of cotton (2015)

208


applied boron on internodes length (cm) of cotton (2014)

209


applied boron on internodes length (cm) of cotton (2015)

209


applied boron on number of monopodial branches of cotton

(2014)

209


applied boron on number of monopodial branches of cotton

(2015)

209


applied boron on number of sympodial branches of cotton

(2014)

210


applied boron on number of sympodial branches of cotton

(2015)

210


applied boron on node for first effective boll bearing

(sympodial) branch of cotton (2014)

210


applied boron on node for first effective boll bearing

(sympodial) branch of cotton (2015)

210

xxxv


applied boron on nodes above white flower (NAWF) of cotton

(2014)

211


applied boron on nodes above white flower (NAWF) of cotton

(2015)

211


applied boron on nodes above cracked boll (NACB) of cotton

(2014)

211


applied boron on nodes above cracked boll (NACB) of cotton

(2015)

211


mepiquat chloride and soil applied boron on phenology of

cotton (2014)

214


mepiquat chloride and soil applied boron on phenology of

cotton (2015)

214


applied boron on days to squaring initiation of cotton (2014)

215


applied boron on days to squaring initiation of cotton (2015)

215


applied boron on days to flowering initiation of cotton (2014)

215


applied boron on days to flowering initiation of cotton (2015)

215


applied boron on days to boll opening initiation of cotton

(2014)

216


applied boron on days to boll opening initiation of cotton

(2015)

216


applied boron on boll maturation period of cotton (2014)

216


applied boron on boll maturation period of cotton (2015)

216


applied boron on mean maturity days of cotton (2014)

217


applied boron on mean maturity days of cotton (2015)

217


applied boron on earliness index of cotton (2014)

217

xxxvi


applied boron on earliness index of cotton (2015)

217


applied boron on production rate index of cotton (2014)

218


applied boron on production rate index of cotton (2015)

218


mepiquat chloride and soil applied boron on thermal time of

cotton (2014)

221


mepiquat chloride and soil applied boron on thermal time of

cotton (2014)

221

4.237 Influence of mepiquat chloride and boron on thermal time

(GDD) taken from sowing to square initiation of cotton

221


(GDD) taken from sowing to square initiation of cotton

221


(GDD) taken from sowing to flowering initiation of cotton

222


(GDD) taken from sowing to flowering initiation of cotton

222


(GDD) taken from squaring to flowering initiation of cotton

222


(GDD) taken from squaring to flowering initiation of cotton

222


(GDD) taken from sowing to boll opening initiation of cotton

223


(GDD) taken from sowing to boll opening initiation of cotton

223


(GDD) taken from flowering to boll opening initiation of

cotton

223


(GDD) taken from flowering to boll opening initiation of

cotton

223


mepiquat chloride and soil applied boron on allometric


226




226


applied boron on vegetative dry matter (g m-2) of cotton (2014)

226

xxxvii


applied boron on vegetative dry matter (g m-2) of cotton (2015)

226


applied boron on reproductive dry matter (g m-2) of cotton

(2014)

229


applied boron on reproductive dry matter (g m-2) of cotton

(2015)

229


applied boron on total dry matter (g m-2) of cotton (2014)

231


applied boron on total dry matter (g m-2) of cotton (2015)

231


applied boron on reproductive-vegetative dry matter ratio of

cotton (2014)

234


applied boron on reproductive-vegetative dry matter ratio of

cotton (2015)

234




235




235


applied boron on crop growth rate (g m-2 d-1) of cotton (2014)

235


applied boron on crop growth rate (g m-2 d-1) of cotton (2015)

235


applied boron on leaf area index of cotton (2014)

238


applied boron on leaf area index of cotton (2015)

238


applied boron on leaf area duration (days) of cotton (2014)

241


applied boron on leaf area duration (days) of cotton (2015)

241


applied boron on net assimilation rate (g m-2 d-1) of cotton

(2014)

241


applied boron on net assimilation rate (g m-2 d-1) of cotton

(2015)

241

xxxviii


mepiquat chloride and soil applied boron on boll distribution

pattern at sympodial branches of cotton (2014)

244


mepiquat chloride and soil applied boron on boll distribution

pattern of cotton (2015)

244


applied boron on percent of first position bolls (%) of cotton

(2014)

244


applied boron on percent of first position bolls (%) of cotton

(2015)

244


applied boron on percent of second position bolls (%) of cotton

(2014)

245


applied boron on percent of second position bolls (%) of cotton

(2015)

245


applied boron on percent of outer position bolls (%) of cotton

(2014)

245


applied boron on percent of outer position bolls (%) of cotton

(2015)

245


mepiquat chloride and soil applied boron on yield and related

attributes cotton (2014)

247




247


applied boron on number of plants m-2 of cotton (2014)

247


applied boron on number of plants m-2 of cotton (2015)

247


applied boron on number of opened bolls per plant of cotton

(2014)

248


applied boron on number of opened bolls per plant of cotton

(2015)

248


applied boron on number of unopened bolls per plant of cotton

(2014)

248

xxxix


applied boron on number of unopened bolls per plant of cotton

(2015)

248


applied boron on total number of bolls per plant of cotton

(2014)

249


applied boron on total number of bolls per plant of cotton

(2015)

249


applied boron on boll weight (g) of cotton (2014)

249


applied boron on boll weight (g) of cotton (2015)

249




251




251


applied boron on number of seeds per boll of cotton (2014)

251


applied boron on number of seeds per boll of cotton (2015)

251


applied boron on seed index (g) of cotton (2014)

252


applied boron on seed index (g) of cotton (2015)

252


applied boron on seed cotton yield (kg ha-1) (2014)

252


applied boron on seed cotton yield (kg ha-1) (2015)

252


applied boron on lint yield of cotton (kg ha-1) (2014)

253


applied boron on lint yield of cotton (kg ha-1) (2015)

253


applied boron on cotton seed yield (kg ha-1) (2014)

253


applied boron on cotton seed yield (kg ha-1) (2015)

253


mepiquat chloride and soil applied boron on fiber quality of

cotton (2014)

256

xl


mepiquat chloride and soil applied boron on fiber quality of

cotton (2015)

256


applied boron on ginning out turn (%) of cotton (2014)

256


applied boron on ginning out turn (%) of cotton (2015)

256


applied boron on fiber length (mm) of cotton (2014)

257


applied boron on fiber length (mm) of cotton (2015)

257


applied boron on micronaire (µg inch-1) of cotton (2014)

257


applied boron on micronaire (µg inch-1) of cotton (2015)

257


applied boron on fiber strength (g tex-1) of cotton (2014)

258


applied boron on fiber strength (g tex-1) of cotton (2015)

258


applied boron on fiber uniformity ratio (%) of cotton (2014)

258


applied boron on fiber uniformity ratio (%) of cotton (2015)

258


applied boron on fiber maturity (%) of cotton (2014)

259


applied boron on fiber maturity (%) of cotton (2015)

259


mepiquat chloride and soil applied boron on photosynthetic

pigments of cotton (2014)

261


mepiquat chloride and soil applied boron on photosynthetic

pigments of cotton (2015)

261


applied boron on chlorophyll a content (mg g-1 FW) of cotton

(2014)

261


applied boron on chlorophyll a content (mg g-1 FW) of cotton

(2015)

261


applied boron on chlorophyll b content (mg g-1 FW) of cotton

(2014)

262

xli


applied boron on chlorophyll b content (mg g-1 FW) of cotton

(2015)

262


applied boron on total chlorophyll content (mg g-1 FW) of

cotton (2014)

262


applied boron on total chlorophyll content (mg g-1 FW) of

cotton (2015)

262


applied boron on chlorophyll a/b ratio of cotton (2014)

263


applied boron on chlorophyll a/b ratio of cotton (2015)

263


applied boron on carotenoids content (mg g-1 FW) of cotton

(2014)

263


applied boron on carotenoids content (mg g-1 FW) of cotton

(2015)

263


mepiquat chloride and soil applied boron on contents of


266




266


applied boron on leaf nitrogen content (mg g-1 DW) of cotton

(2014)

266


applied boron on leaf nitrogen content (mg g-1 DW) of cotton

(2015)

266


applied boron on seed nitrogen content (mg g-1 DW) of cotton

(2014)

267


applied boron on seed nitrogen content (mg g-1 DW) of cotton

(2015)

267


applied boron on leaf phosphorus content (mg g-1 DW) of

cotton (2014)

267


applied boron on leaf phosphorus content (mg g-1 DW) of

cotton (2015)

267

xlii


applied boron on seed phosphorus content (mg g-1 DW) of

cotton (2014)

268


applied boron on seed phosphorus content (mg g-1 DW) of

cotton (2015)

268


applied boron on leaf potassium content (mg g-1 DW) of cotton

(2014)

268


applied boron on leaf potassium content (mg g-1 DW) of cotton

(2015)

268


applied boron on seed potassium content (mg g-1 DW) of cotton

(2014)

269


applied boron on seed potassium content (mg g-1 DW) of cotton

(2015)

269




271




271


applied boron on leaf boron content (µg g-1 DW) of cotton

(2014)

272


applied boron on leaf boron content (µg g-1 DW) of cotton

(2015)

272


applied boron on seed boron content (µg g-1 DW) of cotton

(2014)

272


applied boron on seed boron content (µg g-1 DW) of cotton

(2015)

272


applied boron on leaf zinc content (µg g-1 DW) of cotton (2014)

273


applied boron on leaf zinc content (µg g-1 DW) of cotton (2015)

273


applied boron on seed zinc content (µg g-1 DW) of cotton

(2014)

273

xliii


applied boron on seed zinc content (µg g-1 DW) of cotton

(2015)

273


applied boron on leaf manganese content (µg g-1 DW) of cotton

(2014)

274


applied boron on leaf manganese content (µg g-1 DW) of cotton

(2015)

274


applied boron on seed manganese content (µg g-1 DW) of

cotton (2014)

274


applied boron on seed manganese content (µg g-1 DW) of

cotton (2015)

274


applied boron on leaf iron content (µg g-1 DW) of cotton (2014)

275


applied boron on leaf iron content (µg g-1 DW) of cotton (2015)

275


applied boron on seed iron content (µg g-1 DW) of cotton

(2014)

275


applied boron on seed iron content (µg g-1 DW) of cotton

(2015)

275


mepiquat chloride and soil applied boron on cotton seed


278


mepiquat chloride and soil applied boron on cotton seed


278


applied boron on cotton seed oil content (%) (2014)

278


applied boron on cotton seed oil content (%) (2015)

278


applied boron on cotton seed protein content (%) (2014)

279


applied boron on cotton seed protein content (%) (2015)

279


applied boron on cotton seed ash content (%) (2014)

279


applied boron on cotton seed ash content (%) (2015)

279

xliv


applied boron on cotton seed oil yield (kg ha-1) (2014)

280


applied boron on cotton seed oil yield (kg ha-1) (2015)

280


applied boron on cotton seed protein yield (kg ha-1) (2014)

280


applied boron on cotton seed protein yield (kg ha -1) (2015)

280



to foliar applied mepiquat chloride and soil applied boron

(2015)

287



to foliar applied mepiquat chloride and soil applied boron

(2016)

287

4.371 Maternal induced changes in final emergence percentage (%)


chloride and soil applied boron (2015)

287

4.372 Maternal induced changes in final emergence percentage (%)


chloride and soil applied boron (2016)

287



and soil applied boron (2015)

288



and soil applied boron (2016)

288

4.375 Maternal induced changes in emergence index of cotton


soil applied boron (2015)

288

4.376 Maternal induced changes in emergence index of cotton



288

4.377 Maternal induced changes in root length (cm) of cotton



289

4.378 Maternal induced changes in root length (cm) of cotton



289

4.379 Maternal induced changes in shoot length (cm) of cotton



289

xlv

4.380 Maternal induced changes in shoot length (cm) of cotton



289



mepiquat chloride and soil applied boron (2015)

291



mepiquat chloride and soil applied boron (2016)

291

4.383 Maternal induced changes in root fresh weight (mg) of cotton



291

4.384 Maternal induced changes in root fresh weight (mg) of cotton



291

4.385 Maternal induced changes in shoot fresh weight (mg) of cotton



292

4.386 Maternal induced changes in shoot fresh weight (mg) of cotton



292

4.387 Maternal induced changes in root dry weight (mg) of cotton



292

4.388 Maternal induced changes in root dry weight (mg) of cotton



292

4.389 Maternal induced changes in shoot dry weight (mg) of cotton



293

4.390 Maternal induced changes in shoot dry weight (mg) of cotton



293


in response to foliar applied mepiquat chloride and soil applied

boron (2015)

293


in response to foliar applied mepiquat chloride and soil applied

boron (2016)

293

4.393 Maternal induced changes in seedling vigour index of cotton



294

xlvi

4.394 Maternal induced changes in seedling vigour index of cotton



294

4.395 Coefficients of determination (R2) and correlation coefficients

(r) denoting goodness of fit and association strength between

different variables

296

4.396 Economic analysis 298

4.397 Marginal analysis 299

xlvii

LIST OF FIGURES

Figure

No.

Title Page No.

3.1 Metrological data during the course of present studies (Source:

AgroMet Observatory, Department of Crop Physiology, UAF)

32

3.2 Layout for experiment 1 33

3.3 Layout for experiment 2 34



cotton during 2014 (a) 25 cm (b) 15 cm

85




86


various planting densities on reproductive dry matter (g m-2)

of cotton during 2014 (a) 25 cm (b) 15 cm

89


various planting densities on reproductive dry matter (g m-2)

of cotton during 2015 (a) 25 cm (b) 15 cm

90



during 2014 (a) 25 cm (b) 15 cm

93



during 2015 (a) 25 cm (b) 15 cm

94


various planting densities on crop growth rate (g m-2 d-1) of


100


various planting densities on crop growth rate (g m-2 d-1) of


101


various planting densities on leaf area (cm2) of cotton during

2014 (a) 25 cm (b) 15 cm

103


various planting densities on leaf area (cm2) of cotton during

2015 (a) 25 cm (b) 15 cm

104


various planting densities on leaf area index of cotton during

2014 (a) 25 cm (b) 15 cm

105

xlviii


various planting densities on leaf area index of cotton during

2015 (a) 25 cm (b) 15 cm

106


various planting densities on nutrient use efficiency of cotton

179

4.14 Relationship between boron contents in leaves and relative

seed cotton yield in response to foliar applied mepiquat

chloride and boron at various planting densities

180

4.15 Relationship between boron application rate and relative seed

cotton yield

181


applied boron on vegetative dry matter (g m-2) of cotton (a)

2014 (b) 2015

227


applied boron on reproductive dry matter (g m-2) of cotton (a)

2014 (b) 2015

230


applied boron on total dry matter (g m-2) of cotton (a) 2014 (b)

2015

232


applied boron on crop growth rate (g m-2 d-1) of cotton (a) 2014

(b) 2015

236


applied boron on leaf area (cm2) of cotton (a) 2014 (b) 2015

237


applied boron on leaf area index of cotton (a) 2014 (b) 2015

239

4.22 Influence of foliar applied mepiquat chloride and soil applied

boron on nutrient use efficiency of cotton

283



chloride and soil applied boron

284



chloride and soil applied boron

285

xlix

LIST OF APPENDICES

Appendix

No.

Title Page No.

1 Fixed cost (Rs. ha-1) (Experiment 1) 335

2 Variable cost (Rs. ha-1) (Experiment 1) 336

3 Fixed cost (Rs. ha-1) (Experiment 2) 337

4 Variable cost (Rs. ha-1) (Experiment 2) 338

l

LIST OF ABBREVIATIONS

Abbreviation Complete % percent

°C degree Celsius

µg micro gram

Al aluminum

B boron

BCR benefit cost ratio

C carbon

Ca calcium

CaCO3 calcium carbonate

CEC cation exchange capacity

CER CO2 exchange rate

CGR crop growth rate

Cm centimeter

CO2 carbon dioxide

CRD completely randomized block design

Cu copper

DAS days after sowing

dSm-1 deci simon per meter

DTPA diethylene triamine penta acetic acid

EC electrical conductivity

EDTA ethylene di-amine tetra acetic acid

Fe iron

G gram

GDD growing degree days

GDP gross domestic product

H hour

H2SO4 sulfuric acid

H3BO3 boric acid

ha hectare

ha-1 per hectare

HCl hydro chloric acid

HSD Honest significant difference

K potassium

Kg kilogram

KPa kilo Pascal

L liter

LAD Leaf area duration

LAI Leaf area index

m-2 per square meter

MC mepiquat chloride

Mg Magnesium

mg milligram

mL milli liter

mm milli meter

mmol L-1 milli mole per liter

Mn manganese

li

MRR marginal rate of return

N normal

Na sodium

NACB nodes above cracked boll

NaHCO3 sodium bicarbonate

NAR net assimilation rate

NAWF nodes above white flower

Nm nano meter

NUE nutrient use efficiency

P phosphorus

PGR plant growth regulator

ppm parts per million

R.H. relative humidity

RCBD randomized complete block design

RG II rhammnogalacturonan II

SAR sodium adsorption ratio

SL soluble liquid

SOC soil organic carbon

SP soluble powder

TDM total dry matter

TSS total soluble salts

VCR value cost ratio

w/w weight by weight ratio

Zn Zinc

1

ABSTRACT

Studies on plant growth regulation and boron (B) nutrition for improving earliness,

productivity, quality and nutrient dynamics of cotton were conducted in two field

experiment at Agronomic Research Area, Department of Agronomy, University of

Agriculture, Faisalabad during 2014 and 2015, and two pot experiments at Agro-Biology

Lab Department of Agronomy, University of Agriculture, Faisalabad, Pakistan during 2015

and 2016. In first field experiment the treatments were two planting densities (55333 and

88888 plants ha-1 maintained by varying the plant spacing i.e. 25 and 15 cm, respectively),

foliar application of mepiquat chloride solution (0 and 70 ppm at squarin=-g and flowering

stage) and foliar application of B solution (0, 600 and 1200 ppm). In second field

experiment treatments were foliar application of mepiquat chloride solution (0 and 70 ppm

at squaring and flowering stage) and soil application of B (0, 1, 1.5, 2 and 2.5 kg ha-1).

Water was sprayed as control in both experiments. In pot experiments seed obtained from

both field experiments was used for a soil bioassay to determine the effect of maternal B

nutrition, growth regulation and planting density induced changes on progeny performance

in terms of emergence and seedling growth. The results revealed that plant growth and

development was improved by B nutrition through foliar and/or soil application while

decreased by mepiquat chloride. However, taller plants with lesser monopodial and

sympodial branches were produced at higher planting density. Application of B, mepiquat

chloride and increasing planting density enhanced the earliness and production rate index.

Moreover, dry matter partitioning to reproductive structures was increased by foliar and/or

soil application of B and foliar application of mepiquat chloride. Total dry matter

production as well as dry matter partitioning to reproductive structures was enhanced at

higher planting density. Seed cotton, lint and cotton seed yield was improved interactively

by foliar and/or soil applied B and mepiquat chloride application by improving the number

of bolls and boll weight. Likewise, increasing the planting density produced higher yield

by increasing the boll density; while, foliar applied B significantly interacted with planting

density in this regard. Some of the fiber quality attributes were improved by B, decreased

by higher planting density while did not affect by mepiquat chloride application. However,

the biosynthesis of chlorophyll and carotenoids was improved synergistically by foliar and

/or soil applied B and foliar applied mepiquat chloride but decreased by increasing the

planting density. Oil and protein yield was increased by application of B and mepiquat

chloride, as well as increasing the planting density. Moreover, uptake and translocation of

nutrients (N, P, K, B, Zn and Fe except Mn), nutrient use efficiency (NUE) and critical

value of B was improved by B and mepiquat chloride. Mepiquat chloride application

significantly interacted with B in improving the leaf and seed B contents. However,

increasing the planting density decreased the leaf and seed nutrient contents, and critical

value of B, while, increased the NUE. It was observed that earliness, yield, photosynthetic

pigments, nutritional quality as well as nutrient uptake and translocation was enhanced by

increasing the B dosage (both foliar and soil application) and mepiquat chloride application

at squaring stage. Furthermore, economic analysis also revealed that higher profits and

benefit cost ratio was obtained by foliar application 1200 ppm B solution in combination

with mepiquat chloride (squaring stage) at higher planting density as well as application of

2.5 kg B ha-1 in combination with mepiquat chloride (squaring stage). The soil bioassays

showed that the application of both foliar as well as soil fed B and mepiquat chloride

application on maternal cotton plants improved the emergence, seedling vigour and

biomass accumulation in offspring; while, sowing of maternal plants at higher planting

density imposed a negative effect on these traits.

2

CHAPTER 1

I N T R O D U C T I O N

Cotton (Gossypium hirsutum L.) is cultivated worldwide for fiber and cottonseed

due to its diverse seed composition i.e. fatty acids, oil, protein and mineral nutrition

(Bellaloui et al., 2015). Its oil is used for human consumption and meal for animal feed. It

is an important cash crop of Pakistan and is cultivated for fiber and cottonseed. It also

contributes about 75% to local edible oil production. Pakistan is the fourth largest producer

of cotton in world, third largest exporter of raw cotton, third largest consumer of cotton,

and fourth largest exporter of cotton yarn (ICAC, 2016; Govt. of Pakistan, 2017). It

contributes 5.1% in agriculture value addition and 1.0% in GDP of Pakistan. The area of

Pakistan under cotton during 2016 was 2.5 million hectares with average yield of 0.73 tons

per hectare (Govt. of Pakistan, 2017).

Although Pakistan is 4th largest producer of cotton but the production per unit area

is quite low owing to many restraints including small land holdings, costly agricultural

inputs (seed, fertilizers, pesticides etc.), lack of good quality seed, improper cultivation

methods, unavailability of advanced technologies, scarcity of irrigation water and pest

attack. However, poor soil fertility, ranked growth, poor crop management, and low

planting density are important factors that greatly affect the cotton productivity. Better

management of these variables may help to increase the cotton production (Wells and

Stewart, 2010).

Supply of specific nutrients at proper time, dosage and readily available form is

essential for better growth and development of crop plants. Furthermore, proper crop

nutrition including both macro and micronutrients is essential to achieve higher yield and

quality (Arif et al., 2006). Asian countries are widely becoming deficient in micronutrients

especially B because of low organic matter, high pH, calcareous nature of soils, prolonged

drought and salt stress, imbalanced and more application of NPK fertilizer, irrigation water

with more bicarbonate, B leaching and fixation with clay minerals, and microbial activity

(Shorrocks 1997; Barker and Pilbeam 2007; Malakouti, 2008). Boron deficiency is

considered to be the most wide spread micronutrient deficiency that imparts great

quantitative and qualitative losses in crop production all over the world (Shorrocks, 1997).

The soils of Pakistan are alkaline-calcareous in nature with low organic matter which

3

renders the B deficient in soil (Rashid and Ahmed, 1994). In Pakistan, more than 50% area

is deficient in B (Niaz et al., 2002; Rashid et al., 2005).

Physiologically, B is involved in cell wall synthesis and stability, plasma membrane

activity, cell division, phenol and auxin metabolism, and in the reproductive growth of

plants. In plants, its main role is in sugar metabolism and translocation from source to sink

thus altering the pattern of dry matter partitioning and yield response (Goldbach et al.,

2001; Barker and Pilbeam 2007; Ahmad et al., 2009a). Boron plays a significant role in

leaf chlorophyll synthesis and its activity, stomatal conductance, carbohydrates

translocation and eventually affects the photosynthetic efficiency and dry matter production

(Oosterhuis and Zhao, 2006). Boron deficiency is associated with abnormal growth o f

apical regions normally due to the disturbance in cell wall growth and cell division.

However, the most prominent effects of B deficiency are perceived on plant reproductive

growth. Its deficiency affects the pollen development and pollen tube growth resulting in

male sterility and poor seed set. Moreover, the seeds and fruits abscise prematurely

consequently leading to reduced crop yield (Barker and Pilbeam 2015).

Although cotton is conceived as well adapted to wide range of soils and growing

conditions but it is quite sensitive to B deficiency. In cotton its deficiency results in reduced

plant height and number of nodes, short internodes, fewer squares and fruiting branches,

poor fruit retention, low yield and poor quality (Zhao and Oosterhuis, 2003; Dordas, 2006a;

Ahmed et al., 2013). Furthermore, decrease in assimilate partitioning from leaves to fruits

due to B deficiency causes a decrease in fruiting sites and increase in fruit abscission which

cost for yield (Zhao and Oosterhuis, 2003). Boron deficiency affects the performance of

crops in next generation through decreased germination potential and plant growth (Dordas,

2006a,b). Boron also has significant synergistic and antagonistic interactions with other

nutrients and its deficiency affects their uptake and utilization efficiency. Studies have

revealed positive B interactions with N, P, K, Cu, Zn and Fe, while, negative interactions

with Ca, Mg (Patel and Golakiya 1986; Lopez-Lefebre et al., 2002; Dursun et al., 2010),

and Mn (Sotiropoulos et al., 2002). Various experimental reports within country (Rashid

et al., 2002; Rashid, 2006) and international literature (Gupta, 1993; Shorrocks, 1997) has

revealed the threat of increasing B deficiency in Pakistan; while, suggesting the requisite

of B diagnosis, strategies for improvement in soil B status and measures to enhance the

efficient utilization by crop plants.

Nutrient replenishment is essential for profitable crop production. For this purpose

the essential required nutrients can be applied by fertilization of deficient soils. However,

4

the nutrients applied do not become fully available to crop plants depending on various soil

and plant factors indicating the less than optimum nutrient use efficiency (NUE). Therefore,

to find the means to improve nutrient uptake and translocation to developing seeds for

sustaining the crop productivity and seed nutritional quality along with efficient use of

applied nutrients is an essential goal and challenge of present era.

Plant growth regulators (PGRs) may be employed to improve the crop performance

in terms of yield and quality through modulation of plant growth and physiological

processes such as photosynthetic efficiency, assimilate partitioning and nutrient dynamics

within plant body (Khan et al., 2005; Anjum et al., 2016a). Some studies have provided the

ground basis that exogenously applied PGRs improve crop productivity through enhanced

photo-assimilation and partitioning, and nutrient uptake and translocation to developing

seeds as well within the plant body (Zhao and Oosterhuise, 2000; Nagel and Lambers 2002;

Agegnehu and Taye 2004; Yang et al., 2014; Niu et al., 2016). Thus PGRs offer an

immediate solution to improve the nutrient uptake and use efficiency.

Cotton is perennial in nature having indeterminate fruiting pattern. In irrigated

areas, high irrigation and N inputs are responsible for excessive vegetative growth of cotton

(Abbas et al., 2010) offsetting the partitioning of carbohydrate reserves to vegetative parts

leading to reduced yield and quality (Jost et al., 2006). Plant growth retardant, mepiquat

chloride (1,1-dimethylpiperidinium chloride), limits the vegetative growth of cotton and

alters the pattern of assimilate partitioning, reserve remobilization, and nutrient uptake and

translocation (Sawan et al., 1997; Gwathmey and Clement, 2010; de-Almeida and

Rosolem, 2012). It modulates plant architecture by reducing leaf area, internodes length of

stem and branches, improves light penetration and use efficiency, exalts boll set at lower

sympodial branches and results in improved yield (Nuti et al., 2006; Mao et al., 2014).

Furthermore, it exhilarates leaf CO2 exchange rate, transpiration, stomatal conductance,

chlorophyll content and CO2 fixation (Zhao and Oosterhuis, 2000).

Mepiquat chloride enhances the nutrient uptake and partitioning to reproductive

parts by improving the cotton root growth through enhanced number of lateral roots and

exalted sink size (Zhang et al., 1990; Duan et al., 2004; Sawan, 2013). Sawan et al. (2009)

noticed an increase in uptake and translocation of N and K in mepiquat chloride treated

plants. Similarly, Yang et al. (2014) noticed an increase in N, P and K uptake and

partitioning of K by mepiquat chloride application. Taking together all these factors

positively, it enhances photosynthetic efficiency of plants and exhibits its potential to alter

source-sink relationship by making photo-assimilates and nutrients available for

5

reproductive growth indicating the bolls on treated plants as larger sink for photosynthates

(Gwathmey and Clement, 2010; Sawan et al., 2013). Besides, mepiquat chloride

exacerbates the earlier fruit retention and earliness in crop maturity (Nuti et al., 2006). It

may also improve the fiber and cotton seed quality by increasing the retention of first

position bolls; however, the improvement in fiber quality has been found to be inconsistent

depending upon the timing and dose of the mepiquat chloride application (Sawan et al.,

2009; Ren et al., 2013).

The micronutrients application method and application rate exhibit great

importance regarding the nutrient uptake and use efficiency. The principal methods to apply

micronutrients to cotton are through soil and foliage application. These methods may

enhance the micronutrient contents in treated maternal plants as well as their progeny

(Johnson et al., 2005, Rehman et al., 2014a, Rehman et al., 2015).

Soil application of B improves growth, yield and quality of cotton under B deficient

conditions. Ahmed et al. (2013) reported that soil applied B improved the growth, yield,

and fiber and seed nutritional quality of cotton. Similarly, Ahmed et al. (2011) observed

that soil application of B to cotton enhanced the accumulation of dry biomass and

significantly affected the mineral constitution in plants. An increase in uptake and

translocation of N, P, K, B, Cu and Fe in different parts of plants (leaves, stem, burs, seed

and lint) took place by the influence of B, however, Ca, Mg and Mn concentrations were

lowered than untreated control.

Likewise, foliar applied B helps to cope with B deficiency where the B availability

in soils is reduced due to water deficit and alkaline calcareous nature of soil. Dordas (2006a)

observed that foliar applied B enhanced the plant growth and seed cotton yield from 30-

50% by increasing the percent boll retention than untreated control. Its application also

improved the cotton seed quality determined by enhanced percent seed germination in

germination bioassay and accelerated aging test. Eleyan et al. (2014) revealed that foliar

application of B to cotton aside from enhancing growth and seed cotton yield also enhanced

the earliness of maturity in cotton. It was observed that yield increase was up to 30% while

earliness of maturity was increased up to 4% by the application of B, as compared to

untreated control.

It is known that B requirement of dicots is more than monocot plants due to

difference in cell wall composition of both (Mengel and Kirkby, 2001). Therefore, cotton

has more B requirement. However, being micronutrient the range of B deficiency and

toxicity for cotton is very small in soil and plant tissues viz. 0.5-1.2 mg B kg-1 soil (Rashid,

6

1994) and 20-80 mg B kg-1 leaf blades (Zhao and Oosterhuis, 2002), respectively.

Furthermore, uptake and translocation of nutrients is affected by different management

practices such as by the use of PGRs. Plant growth regulators modulate the vegetative and

reproductive growth but plant nutrition often cannot be kept up with extoled assimilate

partitioning and any nutrient that is deficient becomes the most limiting factor.Therefore

standardization of B application rate by either method (soil and foliar application) along

with PGR application is of utmost importance to improve crop productivity and attain

maximum economic benefits.

Establishment of adequate plant population of cotton is essential to obtain high yield

(Ali et al., 2009a). Hall and Ziska (2000) concluded that plant population should be

increased in order to minimize yield losses. Planting density affects plant growth and

development, lint yield and fiber quality of cotton (Awan et al., 2011). Seed cotton yield is

a function of boll weight and number of bolls per unit area which changes under different

crop and nutrient management practices (Shah et al., 2008; Mao et al., 2014). High planting

density may increase seed cotton yield by raising the number of bolls per unit area

(Gwathmey and Clement, 2010; Dong et al., 2010; Mao et al., 2014). Furthermore, cotton

canopy structure, light interception, fruit formation and dry matter partitioning to fruit alters

with alteration in planting density (Wang et al., 2011, Kaggwa-Asiimwea et al., 2013).

It has been known that reducing the plant spacing and/or increasing the planting

density improves the earliness by decreasing the days to squaring and flowering (Wang et

al., 2011; Munir et al., 2015). However, several studies have reported inconsistent results

pertaining to seed cotton yield. Both increase (Dong et al., 2005; Jahedi et al., 2013) as

well as decrease in yield (Ali et al., 2009b; Ali et al., 2010) has been reported by increasing

the planting density. At high planting density boll retention is reduced due to shading of

lower plant canopy resulting from high leaf area index (Jost et al., 2006) while fiber quality

traits are invariably affected by plant spacing and plant population (Awan et al., 2011).

Moreover, at high planting density inter-plant competition is increased demanding greater

nutrient requirements for sustaining the crop productivity and quality. Seed quality in terms

of germination potential may also be decreased which further limits the crop productivity

in next generation (Merfield et al., 2010). Improvement in seed cotton yield and quality

may occur at high planting density but it requires better canopy and nutrient management

(Siebert et al., 2006; Jahedi et al., 2013).

Although many studies have been conducted to elucidate the effects of mepiquat

chloride and B on cotton separately; however, the information regarding their interactive

7

effect on productivity and quality formation traits is lacking. Furthermore, the positive

effect of mepiquat chloride on improved uptake, translocation and NUE of B has not been

studied as yet. It is also unknown that whether B application in combination with mepiquat

chloride to maternal plants at normal and high planting density improves the seed quality

and performance of progeny plants in next generation. Also the information regarding best

B dose in combination with mepiquat chloride at normal and high planting densities is not

known. It was hypothesized that mepiquat chloride application along with B nutrition can

be used as a tool to improve the cotton yield, fiber and cotton seed nutritional quality by

enhancing the dry matter partitioning to reproductive parts, and nutrient uptake and

translocation in seeds. Moreover, higher planting density can be established to improve the

crop yield and quality through better canopy architecture and nutrient management. Thus

the present study was conducted with following objectives;

a) To standardize mepiquat chloride application in combination with foliar and soil

applied B

b) To evaluate the effect of mepiquat chloride and B application on growth, allometry,

phenology, yield, fiber quality and tissue nutrient contents of cotton at normal and

high planting densities

c) To determine the effect of mepiquat chloride on NUE, critical concentration of B

in leaf tissues and B fertilizer requirement of cotton at normal and high planting

densities

d) To assess the effect of mepiquat chloride and B treatment of maternal cotton on

seed quality in terms of emergence and seedling growth of progeny

8

CHAPTER 2

REVIEW OF LITERATURE

Cotton is an important fiber crop cultivated in many countries of world. Profitable

production of cotton necessitates the continuous supply of essential nutrients and proper

crop management practices. Thus application of required deficient nutrients along with

management of growth factors i.e. rank growth of cotton plants and stand establishment

can improve the nutrient use efficiency, crop yield and quality. The literature regarding B

and crop management practices such as PGRs, B application methods and planting density

is described below.

2.1. Boron

Boron is an essential micronutrient that directly or indirectly influences the plant

growth and development, physiological and biochemical processes. Boron is required for

proper plant growth and development, yield and quality. It is known that, dicots have high

B requirement than monocot plants (Mengel and Kirkby, 2001). Therefore, cotton being

the dicot has more B requirement. The range of B deficiency and toxicity is 0.5-1.2 mg B

kg-1 soil (Rashid, 1994) and 20-80 mg B kg-1 cotton leaf blades (Zhao and Oosterhuis,

2002), respectively. Boron deficiency is spreading throughout the world with wide areas in

some regions of the world and lesser in others, requiring its diagnosis and effective

management practices (Shorrocks 1997; Niaz et al., 2002).

2.1.1. Factors affecting boron availability in soil

Soil is the store house for all the plant essential nutrients and availability of nutrients

to plants is affected by various factors associated with soil. Boron availability to plants is

influenced by various soil properties such as organic matter, texture and clay minerals,

drought, pH, calcareousness and microbial activity (Mengel and Kirkby, 2001). Similarly,

results of some other studies exhibited that there was a considerable relationship among

sodium adsorption ratio (SAR), soil salinity and B on rice germination and seedling growth

(Paliwal and Mehta, 1973). In soil, a small amount of B gradually makes complexes with

organic matter (Gu and Lowe, 1990; Yermiyahu et al., 1995), adsorbed on the clays

(Bingham et al., 1971; Keren and Ben-Hur, 2003) and precipitated with calcium carbonate

and becomes unavailable for optimum growth of crop plants (Shorrocks, 1997). Sandy soils

i.e. coarse textured being well drained are most likely to become B deficient due to leaching

losses (Rashid, 1995; 1996).

9

Soil organic matter considerably affects availability of B (Goldberg, 1997).

Decomposition of organic matter results in an increase in B availability and decrease in its

fixation with clay minerals (Gu and Lowe, 1990). Ligand exchange is the proposed

mechanism behind B adsorption by organic matter (Yermiyahu et al., 1988; Goldberg,

1997). Soil pH alters the B adsorption with organic matter and soil minerals. Soluble B in

soil is found to be positively correlated with pH of soil solution (Mengel and Kirkby, 2001).

Boron is mainly present in soil solution as an undissociated H3BO3 at lower pH (less than

7) (Barker and Pilbeam, 2007) and increase in pH from 7-10 consequences in a prompt

increase in B(OH4)- concentration along with increased B adsorption because of strong

affinity towards clay minerals (Mengel and Kirkby, 2001).

Calcareous soils (high in CaCO3) exhibits high B adsorption (Goldberg and Forster,

1991; Shorrocks, 1997). It has been suggested that the presence of Ca2+ in soil may result

in the formation of calcium-borate ion pair resulting in increased B adsorption (Mengel and

Kirkby, 2001). Similarly, Goldberg (1997) described that the mechanism of B adsorption

in calcareous soils could be the exchange of B with carbonate groups. It has also been

reported that adsorption of B on calcites increases with increased soil solution pH from 6-

9, reaching to a maximum at pH 9.5; subsequently decreases with increase in pH from l0-

11 (Communar et al., 2004). Exchangeable cations present on the clay minerals also affect

adsorption of B (Barker and Pilbeam, 2007). Clay minerals are believed to be primary B

adsorbing surfaces in soil in addition to organic matter, Fe and Al oxides and calcium

carbonate (Goldberg, 1997; Mengel and Kirkby, 2001). The mechanism for adsorption of

B with clay minerals is considered to be the same as proposed for organic matter i.e. ligand

exchange with reactive surface hydroxyl groups (Mengel and Kirkby, 2001; Barker and

Pilbeam, 2007).

The increase or decrease in temperature affects the B adsorption and availability to

plants (Goldberg, 1993). The B adsorption is increased by an increase in temperature

(Fleming 1980). Nevertheless, this could be because of an interaction of soil temperature

and moisture content since the B deficiency is concomitant with hot dry conditions. Soil

moisture considerably impacts upon the B availability. A study revealed that B adsorption

relied upon equivalences and symmetries in the soil moisture contents ranging from 50-

100% of field capacity (Gupta, 1968). On the other hand, Keren and Mezuman (1981)

revealed that adsorption of B was enhanced with decrease in soil moisture content.

Furthermore, some studies on the wetting and drying rotations illustrated that B adsorption

was exalted with increase in wetting and drying cycles (Keren and Gast, 1981).

10

2.1.2. Boron in plant physiology and biochemistry

Boron is an essential mineral nutrient that is required for normal growth and

development of plants. Essentiality of B for plant growth and development has been

established earlier (Shelp, 1993; Marschner, 1995, Shorrocks, 1997, Ahmad et al., 2009b).

The principal functions that B plays in plants relate to the cell wall development and

strengthening, cell division, sugar transport, hormone metabolism and fruit and seed

formation (Marschner, 1995; Herrera-Rodriguez et al., 2010). However, structural role of

B in the cell wall synthesis, and alteration in specific metabolism pathways are considered

to be its main functions in plants (Ahmad et al., 2009b).

It has been found that B has a close relationship with synthesis and functioning of

primary cell wall. Upto 90% of cellular B is found in cell walls. Until now, the well-defined

roles of B in plants are in the cell wall synthesis and intactness through dimerization of

pectic polysaccharide, rhammnogalacturonan II (RG II), by borate cross linking (O’Neill

et al., 2004; Miwa and Fujiwara, 2010b) and plasma membrane integrity (Shelp, 1993;

Marschner, 1995). Besides of cross linking of pectic substances in cell wall, B regulates

the functioning of cell membrane and metabolic activities (Bolanos et al., 2004). Reports

have indicated that B deficiency may cause disruption of membrane functioning, which

affects the other biochemical modifications (Parr and Loughman, 1983; Shelp, 1993).

Boron deficiency affects plasma membrane bound proton pumps (ATPases) hence

influencing the ion flux as revealed in roots of maize (Pollard et al., 1977). Boron supply

augments the activity of ATPases and consequently causes the hyperpolarization of

membrane through stimulation of K+ uptake. The improved pumping activity of plasma

membrane with hyperpolarization leads to an exaggerated driving force for K+ ion influx

(Ahmad et al., 2009b). On the other hand, Cakmak et al., (1995) noticed that B deficiency

affects the membrane permeability as determined through enhanced K leakage from

sunflower leaf cells. Cell division is involved in plant growth and B is directly involved in

it. Cell division is active in growing regions of plants, for example in meristematic tissues.

Boron is structural component of cytoskeleton that is involved in the regulation of cell

division (Bassil et al., 2004). According to Rerkasem (1996) the requirement of B is

particularly higher in meristematic cells as compared to mature tissues.

Boron directly affects the sugar synthesis and translocation in plants. A study

concluded that acute B deficiency increased the concentrations of reducing and non-

reducing sugars but reduced activity of starch phosphorylase in cowpeas (Chatterjee et al.,

1990). Under B deficiency, phenols accumulate in plants because 6-phosphogluconate-

11

borate complex is not formed and the 6-phosphogluconate is converted to the ribulose-5-

phosphate which is substrate for the synthesis of phenolic compounds in shikimic acid

pathway (Mengel and Kirkby, 2001; Barker and Pilbeam, 2007). Oxidation of phenolic

compounds to form quinones and semiquinones by polyphenol oxidase enzyme can

produce reactive oxygen species (ROS) to damage the functioning of plasma membrane

(Ahmad et al., 2009b). Boron also regulates the auxin metabolism through protection of

indole acetic acid oxidase system by complexation of its inhibitors i.e. o-diphenol.

Excessive activity of auxin consequences in excessive proliferation of the cambial cells,

prompt and disproportionate cell expansion, and collapse of the nearby cells (Srivastava

and Gupta, 1996; Barker and Pilbeam, 2007).

Although B is required for proper plant growth and development but its requirement

for reproductive growth is much higher. The most prominent effects of B deficiency are

perceived on plant reproductive growth. Boron is involved in the pollen development,

pollen germination and pollen tube growth (Lee et al., 2009). Its deficiency affects the

pollen development and pollen tube growth resulting in male sterility and poor seed set.

Removal of the external B from growing pollen tubes results in rupturing of pollen tube

tips and abnormal swelling that negatively affects the development of pollen tubes

(Jackson, 1989; Nyomora et al., 2000). Moreover, the seeds and fruits abscise prematurely

consequently leading to reduced crop yield (Barker and Pilbeam, 2015).

2.1.3. Effect of boron deficiency on cotton

The deleterious effects of B deficiency on cotton growth and development has been

well understood from earlier times (Holley and Dulin., 1939; Eaton, 1955; Neirinckx, 1960;

Van de Venter and Currier, 1977; Shorrocks, 1992). In cotton B deficiency causes death of

terminal plant parts, retarded growth, growing of numerous lateral branches with shorter

internodes, crinkled petioles, greater flower and fruit shedding, discoloration of the floral

nectaries, cracks formation on stem and base of the squares, and B deficient plants exhibit

bushy appearance called as rosette (Donald, 1964; Shorrocks, 1992).

Boron deficiency decreases petiole and peduncle cell growth and development

resulting in reduced plant growth of cotton (de Oliveira et al., 2006). Sakal and Singh

(1995) noticed decreased plant growth and development of cotton under B deficient

conditions after 28 days while visible symptoms of B deficiency appeared after 43 days in

the form of chlorotic spots on younger leaves. The leaves turned thick having brittleness

and eventually failed to expand. Moreover, middle leaves exhibited cupping and later on

wilted. They also reported that plants under mild B deficiency produced many lateral

12

branches with rudimentary leaves while under severe B deficiency death of the main stem

occurred.

Boron deficiency significantly affects the synthesis of plant growth, photosynthetic

rate and dry matter production. Rosolem and Costa (2000) reported that even a temporary

B deficiency in cotton plants caused a reduction in plant height, shoot dry biomass

production, and flower and fruit setting. Zhao and Oosterhuis (2003) ascertained the effect

of B deficiency on cotton in a growth chamber study and observed a significant decline in

the plant height, leaf area, rate of leaf net photosynthesis, dry matter accumulation and

fruiting sites. Similarly, Ahmed et al. (2014) reported that B deficiency significantly

increased the cell membrane leakage while reduced the leaf chlorophyll concentration,

photosynthesis, stomatal conductance, intercellular CO2 concentration, transpiration rate

and water use efficiency of cotton.

Yield and quality of cotton is considerably declined by B deficiency. Abid et al.

(2007) observed a decrease in plant height, number of bolls and boll weight leading to

reduction in seed cotton yield under B deficient conditions; however, the fiber quality was

not affected. Ahmed et al. (2013) reported that B deficiency caused a reduction in plant

height, main stem nodes and internodes length, formation of small and distorted bolls,

reduced fruit retention and decreased lint yield of cotton. Bellaloui et al. (2015) observed

that cotton seed composition (oil and protein) and nutrition (mineral nutrients) was

negatively affected by B deficiency and its supplementation through foliar application

improved the nutritional quality.

2.1.4. Augmenting boron nutrition and nutrient use efficiency

Nutrient deficiency is replenished by application of deficient nutrients. However,

optimization of appropriate time, dose, source and method of application of fertilizers is

essential to minimize the nutrient losses for enhanced nutrient use efficiency and profitable

crop production. Moreover, different crop management practices can be employed to alter

the ability of plants to uptake and utilize nutrients for improved nutrient use efficiency,

improved yield and quality.

2.2. Plant growth regulators

Plant growth regulators are the organic or synthetic chemical substances when

applied in small concentrations affect the plant growth and development through

modulation of plant physiological processes (Anjum et al., 2016b). The PGRs have the

potential to improve the yield and quality of crops through modulation of plant growth and

physiological processes such as photosynthetic efficiency and nutrient dynamics within

13

plant body (Khan et al., 2005; Anjum et al., 2016a). Plant growth regulators may be applied

to improve the nutrient uptake and translocation to enhance the nutrient use efficiency. It

has been observed that exogenously applied PGRs improve the nutrient uptake and

accumulation within the plant body by modulating the root growth, enhanced biosynthesis

of photosynthetic pigments, and photo-assimilation and assimilate partitioning (Nagel and

Lambers 2002; Agegnehu and Taye 2004; Gwathmey and Clement, 2010; Niu et al., 2016).

2.2.1. Plant growth retardant

Cotton is perennial in nature and has indeterminate fruiting pattern. Breeding

programs has significantly enhanced the efficiency of yield forming factors of upland

cotton by the selection of traits that are evident in annual crops, together with increased

partitioning of assimilates to reproductive parts (Meredith and Wells, 1989). Some

remnants of the cotton’s perennial nature persist that reduce its efficacy as an annual crop,

such as a quite large proportion of the photosynthates are partitioned to the vegetative

storage tissues (De Souza and da Silva, 1987). In irrigated areas, high irrigation and N

inputs are responsible for excessive vegetative growth of cotton (Abbas et al., 2010) leading

to delayed onset of reproductive growth, increased boll shedding, and reduced yield and

quality (Jost et al., 2006). At peak efficiency, leaves subtending the developing bolls

partition up to 33% of photo-assimilate to the vegetative parts of plant and up to 28% of

the carbon needed for boll maturation comes from storage reserves (Constable and Rawson,

1980). Cotton production would benefit from partitioning that favored the distribution of

stored carbohydrates to reproductive structures (Pace et al., 1999; Gwathmey and Clement,

2010). This shows the need of improving the partitioning of photo-assimilates and

remobilization of stored reserves from vegetative parts to reproductive parts in order to

improve the productivity.

Plant growth and architecture are influenced by environmental conditions and

genetic constitution of the plants which can be manipulated by changing the growth

conditions. Plant growth retardant limits the vegetative growth of cotton and exerts

modifications in plant growth and structure. Plant growth retardants are natural or synthetic

chemical substances that can be applied directly on plants to alter vital processes taking

place within plant body and limit the vegetative growth of plant by modifying hormonal

balance. Mepiquat chloride (1,1-dimethylpiperidinium chloride) is a plant growth retardant

that limits the vegetative growth of cotton and alter the pattern of assimilate partitioning

and reserve remobilization (Gwathmey and Clement, 2010; de-Almeida and Rosolem,

2012). The decrease in growth by mepiquat chloride occurs due to decreased biosynthesis

14

and concentration of gibberellic acid within plant cells which consequences in reduced cell

wall plasticity and cell size (Rademacher, 2000; Wang et al., 2014). Mepiquat chloride

alters the growth and architecture, and improves the nutrient uptake and translocation by

crop plants leading to changes in dry matter production and partitioning, earliness, yield

and quality response.

2.2.1.1. Plant growth and architecture

Mepiquat chloride reduces the plant growth and development, and causes an

alteration in plant architecture. Reduced plant height, main stem nodes, internodes length

of main stem and branches, vegetative branches and leaf area are morphological responses

of plants to mepiquat chloride. Although plant height and leaf area of plants is reduced but

the production of new leaves and reproductive structures remains unaffected while dry

matter production per plant is increased (Han, 1991; Zhao and Oosterhuise, 2000; Abbas

et al., 2010). Çopur et al. (2010) reported a decrease in plant height and number of

sympodial branches by application of mepiquat chloride and attributed this decrease to

decreased biosynthesis of gibberellic acid. Dodds et al. (2010) observed that application of

mepiquat chloride reduced the plant height, number of main stem nodes and decreased the

number of nodes above last cracked boll (NACB) bearing branch.

Boll position significantly affects the boll retention and yield response; which in

turn is closely related to plant growth and architecture. It has been found that plant growth

retardants decrease the plant growth and alter the sympodial branches and bolls positions

as well as boll retention percentage. Wilson et al. (2007) reported that application of

mepiquat chloride decreased the plant height and number of main stem nodes along with

altering the first sympodial branch position on main stem node. Furthermore, application

of mepiquat chloride enhanced the percentage of first position bolls and boll retention

percentage. Gwathmey and Clement (2010) evaluated the impact of mepiquat chloride on

cotton and reported that application of mepiquat chloride showed significant effect on plant

growth and architecture. It lowered the plant height, leaf area index and stem diameter;

while, increased the percentage of boll set at lower sympodial branches. Similarly, Mao et

al. (2015) reported that application mepiquat chloride modified the boll distribution pattern

with reference to the sympodial branches on main stem. The bolls were more concentrated

on lower and middle positioned sympodial branches on main stem in response to mepiquat

chloride while it reduced the number of bolls at upper sympodia and this trend was

strengthened with increase in dose of mepiquat chloride.

15

2.2.1.2. Dry matter production and partitioning

Mepiquat chloride application is known to affects the dry matter partitioning from

vegetative to reproductive parts but its effect on dry matter production has been inconsistent

although it enhances the leaf chlorophyll synthesis and rate of photosynthesis. Zhao and

Oosterhuise (2000) reported that application of mepiquat chloride to cotton improved the

rate of CO2 exchange, transpiration, CO2 fixation and photosynthesis. However, it did not

show any effect on dry matter production but enhanced assimilate and dry matter

partitioning from stem to leaves and fruits. Similarly, de-Almeida and Rosolem (2012)

observed that mepiquat chloride applied through seed did not affect the dry matter

production in cotton.

Plant height and leaf area index (LAI) are reduced by mepiquat chloride that leads

to improved light penetration and distribution within plant canopy that ultimately improves

the light utilization efficiency and dry matter production in some instances. Gonias et al.

(2012) observed a significant effect of mepiquat chloride on growth, dry matter partitioning

and radiation use efficiency of cotton. They reported that there was a reduction in plant

height and LAI of cotton, while, dry matter partitioning from leaves and stem to bolls was

increased resulting in increased radiation use efficiency. Alteration in plant growth and

architecture such as a decrease in plant height and LAI by the application of mepiquat

chloride on cotton improved the light distribution within plant canopy and light utilization

efficiency which resulted in increased photosynthetic efficiency. However, the above

ground biomass production was only affected when mepiquat chloride was applied at high

planting densities but the partitioning of dry matter to different plant parts was significantly

affected with increased partitioning to leaves and reproductive parts (Mao et al., 2014).

2.2.1.3. Nutrient dynamics and use efficiency

Manipulation in plant growth and architecture by mepiquat chloride application

alters the pattern of nutrient uptake and translocation within plants. It has been observed

that mepiquat chloride significantly affected the nutrient profile in cotton plants under

different nitrogen regimes (Heilman, 1985). The differential uptake by mepiquat chloride

treated and untreated plants is considered to be related to the root growth of plants.

Mepiquat chloride enhances the root growth of plants by increasing the number of lateral

roots (Li, 1990; Tang, 1992), increase root vigor by increasing the reducibility and

respiratory rate and thereby increases the uptake of N, P and K (Jin et al., 1984; He et al.,

1988; Zhang et al., 1990; He et al., 1991; Duan et al., 2004).

16

Modulation of source-sink relationship by mepiquat chloride might also be

conceived as a reason of improved uptake of nutrients. Application of mepiquat chloride

enhances the leaf chlorophyll concentration and photosynthesis (Zhao and Oosterhuis,

2000) which have a direct relation with nutrients uptake and assimilation (Horchani et al.,

2010; Pavlovič et al., 2010). It has been observed that reduction in vegetative growth shifts

the balance from vegetative to reproductive growth accompanied by enhanced partitioning

of nutrients towards developing bolls; consequently, the nutrient uptake is increased to

compensate the demand of plants for nutrients (Kerby et al., 1996).

Mepiquat chloride improves the sink size that exalts the translocation of nutrients

towards reproductive parts and indirectly increases the nutrient uptake (He et al., 1991;

Sawan, 2013). Application of mepiquat chloride enhances early boll set at lower sympodial

positions and increases the boll retention percent (Nuti et al., 2006). Furthermore, it

enhances the seed set and development by shifting the resources from vegetative to

reproductive growth (Sawan et al., 2001; Sawan, 2007). This causes a higher demand for

nutrients to fulfil the need of developing bolls and seeds for nutrients and thus higher

nutrient uptake and translocation occurs. Sawan et al. (2009) reported that application of

mepiquat chloride exalted the nutrient (N, P and K) uptake and translocation in cotton, and

it was related to improved seed size and seed yield.

It has been observed that application of mepiquat chloride improves the nutrient

uptake and use efficiency. Yang et al. (2014) reported that application of PGRs (mepiquat

chloride and miantaijin) enhanced the K use efficiency in cotton. They further observed

that PGRs improved the K recovery efficiency and suggested that it was associated with

enhanced K uptake and translocation to different plant parts such as stalk, seed and lint.

Furthermore, according to Khan et al. (2005) increase in the N recovery efficiency by PGR

application was related to enhanced plant growth, leaf CO2 exchange rate (CER), and

uptake and accumulation of N. Also, PGRs (trinexapac-ethyl and paclobutrazol) could

increase soil organic carbon (SOC), thus increasing soil’s cation exchange capacity (CEC)

or its capability to hold on and supply the essential nutrients viz. Mg, K and Ca, and

accelerate the decomposition of minerals in soil over time, making the nutrients available

in minerals for uptake by plants (López-Bellido et al., 2010).

2.2.1.4. Earliness

Early maturity is one of the desirable characters in cotton production in shorter

growing seasons where the relative maturity is shortened. Earliness is generally measured

as percentage of the total harvestable opened bolls with that of total bolls. Theoretically,

17

enhanced earliness is because of increased percent of boll retention at lower sympodial

positions in fruiting profile, thus providing the potential benefits of cotton production with

short growing seasons (Kerby et al., 1986). Mepiquat chloride application improves the

earliness of cotton production by decreasing the vegetative growth as enhanced earliness is

accompanied by decreased vegetative growth and shift of resources from vegetative to

reproductive parts thus providing the adequate time for bolls to mature. Reduction in

vegetative growth by mepiquat chloride shifts the nutrient resources to developing bolls

with a higher proportion of bolls at lower nodal positions (Kerby et al., 1996; Wilson et al.,

2007).

Physiological maturity is enhanced by mepiquat chloride through earlier cutout as

measured by nodes above white flower (NAWF = 5) consequently leading to greater first

harvest percentage (Gwathmey and Craig, 2003). Johnson et al. (2006) reported an increase

in earliness indexed through percent of first harvest and it was related to earlier decrease in

NAWF than untreated control. Similarly, Çopur et al. (2010) observed an increase in

earliness index (percent of first harvest) by mepiquat chloride application at first flowering

and two weeks after first flower. Nodes above cracked boll is another index of measuring

earliness of cotton production. Dodds et al. (2010) noticed a decrease in nodes above

cracked boll with mepiquat chloride application. Similarly, Samples et al. (2015) reported

a decrease in NACB by mepiquat chloride application and it was well correlated with

decrease in plant height.

2.2.1.5. Yield and related attributes

Mepiquat chloride application enhances earlier and greater boll retention, and

increases boll size as compared to untreated control. It has been observed that mepiquat

chloride concentrates the boll set at lower sympodial branches and enhances the first

position bolls (Wilson et al., 2007). Bolls at lower sympodial branches and first positions

tend to be heavier because they obtain assimilates directly from subtending leaves and by

rule the sink nearer to source acquires relatively higher share of resources (Jost et al., 2006;

Mao et al., 2015). Furthermore, mepiquat chloride enhances the earlier boll set and

decreases boll shedding which ultimately results in enhanced bolls density, bolls weight

due to more time available for maturing the bolls and yield (Gwathmey and Craig, 2003;

Ferrari et al., 2015).

Various studies have shown improved yield of cotton by application of mepiquat

chloride. Wilson et al. (2007) reported that application of mepiquat chloride in different

application strategies (low rate multiple, modified early bloom and early

18

bloom) enhanced lint yield and it was associated with greater boll retention, as compared

to control. Cheema et al. (2009) observed that mepiquat chloride application decreased the

plant growth while increased seed cotton yield up to 18% over untreated control. Similarly,

Abbas et al. (2010) reported that mepiquat chloride application reduced the plant growth

and improved the seed cotton yield owing to the more number of bolls per plant and greater

boll weight by the application of mepiquat chloride. A yield increase up to 10% was noticed

by treatment with mepiquat chloride as compared to untreated control.

The efficacy of mepiquat chloride in improving yield is affected by different

environmental conditions. Gwathmey and Clement (2010) noticed that the efficacy of

mepiquat chloride in improving lint yield of cotton was greater at high planting densities

than at lower planting densities due to reduction in canopy leaf area per unit land area.

Yang et al. (2014) assessed the effect of mepiquat chloride on cotton under K deficient and

adequate conditions. They observed that although the lint yield was improved by mepiquat

chloride application under both conditions but the yield improvement under K adequate

conditions was much higher. Mao et al. (2014) reported that multiple application of

mepiquat chloride especially involving the squaring stage caused more increase in lint yield

of cotton as compared to single application. Moreover, Mao et al. (2015) noticed the effect

of dry and wet years on the efficacy of mepiquat chloride regarding lint yield. The lint yield

was more during wet year as compared to dry years indicating that dry seasons reduce the

efficacy of mepiquat chloride. They further observed that warm and dry season during the

late boll maturation phase aided the mepiquat chloride in increasing the boll retention and

lint yield.

2.2.1.6. Fiber quality

The effects of mepiquat chloride on fiber quality have been found inconsistent. In

fact mepiquat chloride has no direct effect on fiber quality. It improves the fiber quality

through enhanced boll set at lower canopy and increasing the boll set at first positions; as

the bolls at these positions are superior in lint and fiber quality. Çopur et al. (2010) observed

a significant increase in lint percentage of cotton by mepiquat chloride application but non-

significant effect on fiber length, fineness, strength and uniformity. Dodds et al. (2010)

reported a significant decrease in lint percentage, increase in fiber length while non-

significant effect of mepiquat chloride on micronaire, fiber strength and uniformity of

cotton. However, Ren et al. (2013) said that mepiquat chloride application decreased lint

percentage while increased the fiber length and strength of cotton at low as well as high

19

planting densities. Similarly, Samples et al. (2015) reported an increase in fiber length,

strength and uniformity by mepiquat chloride application at higher rates on cotton.

2.2.1.7. Cotton seed quality

Cotton seed has a diverse composition (protein, oil, fatty acids and mineral

nutrients). Cotton seed oil is used by human and cotton seed meal is utilized for animal feed

(Bellaloui et al., 2015). Cotton seed oil production has gained third position after the

production of rapeseed and soy bean (USDA-ERS, 2013). Cotton seed has got much

importance due to its high protein contents (17-27%), oil contents (12-30%), and saturated

and unsaturated fatty acids (approximately 29 and 70%, respectively) (Dowd et al., 2010;

Pettigrew and Dowd, 2011). Various environmental and management practices influence

the cotton seed composition despite of genetic control (Pettigrew and Dowd, 2011;

Bellaloui et al., 2015).

Mepiquat chloride application affects the cotton seed composition. It enhances the

cotton seed protein and oil contents as compared to untreated control (Sawan et al., 2007).

It has been observed that mepiquat chloride improves the seed protein contents due to its

role in protein synthesis through enhanced conversion of amino acids into protein (Wang

and Chen, 1984). Whereas, improvement in oil content by mepiquat chloride application is

suggested to be due to improved photo-assimilation and translocation of photosynthates in

seeds (Zhao and Oosterhuis, 2000; Gwathmey and Clement, 2010). Saturated and

unsaturated fatty acids profile is affected significantly by mepiquat chloride. In a study it

was noticed that application of mepiquat chloride decreased the saturated fatty acids

(palmitic, myristic, capric and stearic acid) while increased unsaturated fatty acids (oleic

and linoleic acid) in cotton seed (Sawan et al., 2007).

Aside from seed composition and oil quality, mepiquat chloride also affects the seed

quality in terms of viability and vigour. Sawan et al. (2009) ascertained the effect of

mepiquat chloride on seed viability and vigour. The results showed that it improved the

seed viability and vigour as exhibited by cold test and it was related to improved assimilate

and nutrients translocation in seeds. In another study, Sawan et al. (2013) observed that

mepiquat chloride improved the final germination count, germination velocity and seedling

vigour of cotton.

2.3. Boron application methods

Nutrient uptake and use efficiency is influenced by application method. Maximum

benefits of any applied nutrient can be harvested when it is applied in adequate amount and

delivered to plants efficiently (Rehman et al., 2014a). Moreover, proper method, time and

20

source of nutrients is extremely important for optimal plant growth and yield (Rehman et

al., 2014b; Rehman et al., 2015). It is also necessary to know that how the applied nutrients

are affected by soil, plant and environmental factors. Micronutrients such as B can be

applied by different methods such as soil application, foliage application and seed treatment

(Rehman et al., 2016). However, soil and foliar application are the principal methods of B

application that may be employed to overcome its deficiency.

2.3.1. Soil application

The application of B is mainly accomplished by soil application. It ensures the early

and continuous availability of the nutrient to crop plants. Ahmad and Irshad (2011)

suggested that B can be applied at any growth stage of cotton by this method; however, the

nutrient use efficiency differs with growth stage. The B availability to plants is decreased

by various soil factors such as high soil pH, low soil moisture and organic matter, soil

microbial activity and calcareousness (Shorrocks, 1997). Soil applied B improves the soil

B status under B deficient conditions that ensures the better growth, yield and quality of

crop plants (Rehman et al., 2014a, 2015, 2016). Görmüş (2005) found that soil applied B

at the rate of 1.12 kg ha-1 enhanced the seed cotton yield and lint yield and it was associated

with enhanced number of bolls and boll weight. Moreover, lint percentage, fiber elongation

and fiber uniformity was also improved by soil applied B.

A study was conducted by Abid et al. (2007) to assess the effect of soil applied B

on cotton and revealed that growth, yield and value cost ratio (VCR). It was attributed to

improved boll retention percentage and boll weight of cotton. Maximum improvement in

growth and yield was occurred by 2 kg B ha-1 while highest VCR was observed by 1.5 kg

B ha-1. However, the soil applied B did not improve the fiber quality. Ahmed et al. (2011)

reported that soil application of B improved the dry matter production and mineral

constitution in plants. Boron application upto 3 kg ha-1 boron exalted N, P, K, B, Cu and

Fe while decreased the Ca, Mg and Mn contents in leaves, stem, burs, seed and lint of

cotton. Ahmed et al. (2013) ascertained the effect of soil applied B on seed cotton yield,

fiber and seed quality. They found that application of 2-2.5 kg B ha-1 improved the plant

height, number of nodes, number of bolls, boll weight and seed cotton yield. The fiber

quality was not affected significantly; however, cottonseed protein and oil contents were

improved significantly. Similarly, Saleem et al. (2016a) reported that soil application of

1.5-2 kg B ha-1 improved the seed cotton yield through improved boll retention percentage

and leaf boron content. However, benefit cost ratio (BCR) was improved by 1.5 kg B ha-1.

21

2.3.2. Foliar application

Foliar application of plant nutrients may enhance the plant growth, yield and NUE

as well owing to the rapidity with which the most requiring nutrients are provided to the

plants for better growth and yield (Oosterhuis and Weir, 2009; Habib, 2012). Foliar nutrient

solution has nutrients that are absorbed quickly, with fewer nutrients the utilization is high,

and it may relieve plant nutrient deficiency symptoms, increase yield and improve plant

physiological and biochemical functions (Rehman et al., 2014b). Dordas (2006a) assessed

the effect of foliar applied B on cotton and found that plant height, seed cotton yield, lint

yield and cotton seed yield was increased due to increase in boll retention and boll weight.

Moreover, NUE, lint fraction and seed quality in terms of viability and vigour was also

improved by foliar applied B at 800-1200 ppm concentration.

A study revealed that foliar application of B improved the seed cotton yield. It also

improved the ginning out turn as well as fiber length and micronaire of cotton (Ahmad et

al., 2009a). Similarly, Ali et al. (2011) reported that foliar applied B improved the number

of bolls, boll weight and seed cotton yield. The VCR was also improved by foliar

application of B as compared to control. Rashidi et al. (2011) conducted an experiment to

determine the effect of foliar applied B on cotton and found that number of bolls, boll

weight, seed cotton yield and leaf blade B concentration was increased. Moreover, foliar

boron also improved the fiber length and fiber fineness of cotton. Eleyan et al. (2014)

revealed that application of B to cotton aside from improving the growth and seed cotton

yield also enhanced the earliness in cotton. It was observed that yield increase was up to

30% while earliness was increased up to 4% by the application of B, as compared to control.

2.4. Planting Density

Cotton production is greatly influenced by plant population density. Planting

density has been shown to exert considerable influence on growth and development of crop

plants, dry mater partitioning, seed cotton yield and earliness. Planting density affects the

plant architecture, photosynthesis and yield formation of cotton (Board, 2001; Zhang et al.,

2006). Row spacing and planting densities can be adjusted to manipulate the plant canopy

architecture for yield improvements, production efficiencies and monetary benefits

(Silvertooth, 1999). It has been observed that adjustment of planting densities is an easy

approach to improve the crop yield profitability.

It has been observed that at wider plant spacing or lower planting densities weeds

grow vigorously (Prasad and Prasad, 1993), plants become highly vegetative at the expense

of yield (Ogola et al., 2006) and harvest efficiency is reduced (Gannaway et al., 1995). On

22

the other hand, closer plant spacing or high planting densities may cause an increase in intra

plant competition for nutrients and moisture contents, and often leads to build up of insect

pests in plant canopy with the consequence of yield reductions (Ogola et al., 2006).

However, it has been observed that increase in planting density increases the LAI and lint

yield, but area of the individual leaves is decreased (Gwathmey and Clement, 2010). This

shows that higher planting densities may be established to improve the crop productivity.

Hall and Ziska (2000) suggested that plant population should be increased in order to

minimize yield losses.

The plant population density affects the plant growth and architecture, dry matter

production and partitioning, earliness, yield and quality.

2.4.1. Plant growth and canopy structure

Plant canopy structure (shape, size and orientation of the shoot components) is one

of the important agronomic attributes that significantly affects the crop adaptability,

resistance to insect pests and diseases, establishment of planting density, light penetration

and distribution within plant canopy, ease of crop harvest and yield formation (Maddonni

et al., 2001; Marois et al., 2004; Stewart, 2005). Although planting density is determined

on the basis of plant canopy architecture; contrary, the plant canopy may be modified by

manipulating planting density regardless of its genetic control. A study revealed that cotton

plant growth was affected significantly by varying planting density. There was a reduction

in number of nodes while an increase in plant height by increasing planting density showing

increase in inter nodal length of plants. Conversely, the monopodial branches were lowered

at higher plant population, as compared to lower planting density (McCarty et al., 2011).

In another study Kaggwa-Asiimwe et al. (2013) reported similar results that

increase in planting density of cotton from 57,300-66,500 plants ha-1 to 126,700-146,000

plants ha-1 for two contrasting cultivars in canopy structure i.e. Delta and Pine 164B2RF

(columnar type) and Stoneville 4498B2F (bush type), respectively, caused an increase in

plant height and LAI while decrease in number of nodes consequently leading to increased

internodes distance. Mao et al. (2015) observed that increasing the planting density from 3

to 7.5 plant m-2 affected the distribution of harvestable bolls with respect to main stem

nodes. The increase in planting density shifted the number of harvestable bolls from middle

and higher nodes to the lower canopy of plants.

2.4.2. Dry matter production, partitioning and crop growth rate

High plant density obtained by narrow row spacing produces greater dry biomass

per unit area (Darawsheh et al., 2007, 2009) and LAI (Darawsheh et al., 2009)

23

as compared to the conventional row spacing system of cotton. However, per plant dry

weight and leaf area are reduced with high plant density as compared to low plant density

(Wankhade et al., 2002). Furthermore, the net assimilation rate (NAR) is decreased with

high planting density (Bednarz et al., 2000). In a study, Ali et al. (2009a) observed a

significant effect of different plant spacing on crop growth rate (CGR) and dry matter

partitioning of cotton. The results of the study revealed that highest increase in plant growth

rate and dry matter partitioning to reproductive parts was occurred at lower plant spacing

(15 cm) with maximum planting density. Wang et al. (2011) reported an increase in dry

matter production and partitioning of higher dry matter to reproductive parts at high

planting density (1500000 plants ha-1). Similarly, Kaggwa-Asiimwe et al. (2013) observed

alteration in plant architecture, and increase in biomass accumulation and partitioning of

cotton by increasing planting density. They found that with high planting density (126,700-

146,000 plants ha-1) the biomass partitioning to bolls was increased with a decrease in

biomass partitioning to vegetative parts.

2.4.3. Earliness

It has been known that reducing the plant spacing and/or increasing the planting

density improves the earliness in cotton (Wang et al., 2011). In fact, the main purpose of

narrow row, high planting density was to enhance the earliness of crop maturity and reduce

production cost of cotton (Buxton et al., 1979; Gerik et al., 1999). Plants in high planting

density system produce lesser main stem nodes and short sympodial branches, bolls are

more concentrated near to the main stem which is favorable to enhances early crop maturity

(Oad et al., 2002). In a study, Obasi and Msaakpa (2005) reported that wider plant spacing

reduced the days to first open boll and earliness index. Wilson et al. (2007) assessed the

effect of planting density on cotton and found that high plant density improved the boll

retention at first sympodial positions and enhanced the earlier boll retention, as determined

by bolls set at lower sympodial nodes. Similarly, another study results concluded that

reducing the row spacing resulted in significant improvement in earliness index and it was

associated with reduction in earlier fruit retention as indicated by lower fruiting branch

node, and days to squaring and flowering (Munir et al., 2015). Earliness index is most

commonly used trait to estimate the earliness in cotton maturity (Bourland et al., 2001).

Saleem et al. (2009) narrated that narrow-rows or high planting density is advantageous for

earliness in cotton maturity mainly due to shortening of growing season.

24

2.4.4. Yield and related attributes

Seed cotton yield is a function of boll density (bolls m-2) and boll weight. At high

planting density the boll density is increased that leads to improved seed cotton yield;

although the number of bolls per plant and individual boll weight are decreased at high

planting densities (Ali et al., 2009a; Mao et al., 2015). Increase in planting density typically

results in decrease in number of bolls and boll weight due to increased shading of lower

canopy, decreased light penetration and distribution within plant canopy and decreased

photosynthetic efficiency of plants (Mao et al., 2014; Xue et al., 2015; Yao et al., 2015).

Several studies have reported inconsistent results pertaining to seed cotton yield.

Both increase and decrease in yield has been reported by increasing the planting density

under different management practices. Dong et al. (2005) and Jahedi et al. (2013) noticed

an increase in seed cotton yield by increasing plant population per unit area. However, Ali

et al. (2009b) and Ali et al. (2010) observed that seed cotton yield was lowered by

increasing the plant population per unit area.

The yield response of cotton to planting density varies with various factors such as

plant architecture, soil nutrient status, weather and environmental conditions (rainfall,

temperature and humidity) and crop management (Ren et al., 2013; Yao et al., 2015). It has

been observed that high planting densities are favored under conditions in which less

vegetative growth occurs (such as hot dry) while lower planting densities are preferred

under high growing conditions (Dong et al., 2012; Ren et al., 2013). Furthermore, canopy

and nutrient management practices also allows for the establishment of high planting

densities without any yield losses (Kaggwa-Asiimwe et al., 2013; Yang et al., 2014).

2.4.5. Fiber and cottonseed quality

Fiber quality attributes are invariably affected by plant spacing and plant

population. Wrather et al. (2008) assessed the effect of planting densities ranging from

23782 to 135904 plants ha-1 on fiber quality traits of cotton. They found that planting

density did not impose a significant effect on any of the studied fiber traits i.e. lint

percentage, and fiber strength, length, micronaire and elongation. Awan et al. (2011)

reported that some fiber traits were significantly affected by planting density while most of

the fiber traits were non-significant. It was perceived that fiber strength and ginning out

turn was increased significantly at 30 and 20 cm row spacing, respectively; however, staple

length, uniformity index and fiber fineness were not affected significantly. Similarly,

Jahedi et al. (2013) reported that fiber length and fiber strength was decreased by increasing

25

planting density showing an inverse relationship. However, fiber fineness was not affected

significantly by planting density.

Plant density affects the cotton seed yield and quality in terms of nutrition, and

viability and vigour. Merfield et al. (2010) reported that planting density imposed a

significant effect on seed quality in terms of germination and seed vigour of carrot.

Increasing the planting density resulted in decrease in seed viability and vigour and it was

associated with seed size. Similarly, Lili et al. (2010) observed a negative correlation of

planting density with cotton seed biomass, fat and protein contents and followed a pattern

of quadratic curve. Xiao-yu et al. (2016) reported that increase in planting density

decreased the seed surface area and seed vigour index.

2.5. Management of high planting density

Recent trends in cotton production are increasing planting densities to reduce yield

losses and increase benefits (Hall and Ziska, 2000). However, at high plant density

increased LAI causes the mutual shading of lower plant canopy leading to high boll

shedding. The early fruit loss results in increased plant height because carbohydrates and

nutrients get directed towards vegetative growth (Jost et al., 2006). Excessive plant height

may be difficult to manage pests, defoliation and harvesting. Additionally, the management

of excessive plant height of cotton is difficult with reduced boll retention (Hake et al.,

1990). The balance in vegetative and reproductive growth is essential for obtaining high

crop yield. Furthermore, high planting densities require a compact plant canopies to ensure

better light interception and distribution (Mao et al., 2014). This necessitates the

management of crop nutrition and excessive vegetative growth of cotton plants at high

planting densities.

Optimization of fertilizers application with high planting density is necessary for

obtaining high yield with minimum nutrient losses (Li-jun et al., 2012). It has been

observed that needs of the crop plants for nutrients differ with varying planting densities

(Dong et al., 2010). Moreover, application of high rates of fertilizers cause excessive

vegetative growth of plants thus reducing the yields, wasting expensive nutrient inputs and

causing the environmental pollution (Zimmermann et al. 2006). Hussain et al. (2000)

evaluated the effect of N at different planting densities of cotton. The cotton yield was

increased with increasing N rates and planting density or reducing the plant spacing.

Similarly, Dong et al. (2010) observed that application of N and K with high planting

density at low fertility level increased the cotton yield; however, under high fertility status

only K application increased the yield at high planting density. Boron is deficient

26

micronutrient and affects the growth and development, and yield and quality of cotton

plants (Görmüş, 2005; Dordas, 2006a; Ahmed et al., 2011; Ahmad and Irshad, 2011).

Therefore, optimization of its application rates at different plating densities of cotton is

necessary.

Application of mepiquat chloride on cotton exhibits various consequences for

canopy structure and function of plant (Reddy et al., 1996; Zhao and Oosterhuise, 2000;

Gonias et al., 2012). Mepiquat chloride application results in compact plant structure and

decreases the formation of late season bolls that are otherwise unable to reach maturity

before the growing season ends (Mao et al., 2014). Various studies have demonstrated the

beneficial effects of mepiquat chloride at high plant densities of cotton. Wilson et al.

(2007), and Mao et al. (2014, 2015) reported that high planting density increased the plant

height and LAI of cotton while mepiquat chloride application decreased the vegetative

growth enhancing the dry matter partitioning to reproductive structures and lint yield.

Gwathmey and Clement (2010) noticed that lint yield was decreased by decreasing the

plant spacing and/or increasing planting density however mepiquat chloride improved the

lint yield at each plant spacing. Ren et al. (2013) reported that application of mepiquat

chloride improved the fiber quality although caused a little bit decrease in lint yield.

2.6. Conclusion

Boron deficiency affects the growth, yield and quality of crops. In cotton, B

deficiency results in decreased yield due to reduction in boll retention. Moreover, it affects

the cotton seed quality due to decrease in uptake and translocation of nutrients. Boron can

be applied by different application methods with principal method being foliar and soil

application. Plant growth retardant, mepiquat chloride, has the potential to enhance the crop

productivity, and nutrient uptake and use efficiency. Cotton yield and B use efficiency can

be improved by application of mepiquat chloride along with B nutrition. Moreover,

planting density can be manipulated to improve the crop yield and NUE. However,

management of canopy structure and deficient nutrients is required to achieve the potential

benefits of high planting density.

27

CHAPTER 3

MATERIALS AND METHODS

Study was conducted to evaluate the effect of plant growth retardant and B

application on growth, allometry, phenology, physiology, yield and quality of cotton in two

field experiments and two laboratory experiments, each for two consecutive years during

2014-16.

3.1. General

3.1.1. Site

The study was conducted in the Agrobiology lab, Department of Agronomy and

Student Research Area, Department of Agronomy, University of Agriculture, Faisalabad

(31.25 ºN latitude, 73.09 ºE longitude, 184 m above sea level) during 2014-16.

3.1.2. Experimental material

The seed of cotton variety MNH-886 was used for experiments in course of present

study. The seed was procured from Punjab Seed Corporation, Ayub Agriculture Research

Institute, Faisalabad, Pakistan. The germination percentage of seed was 70%. Mepiquat

chloride [98% SP from Henan Haoyuhang Economic and Trade Co., Ltd] was used as plant

growth retardant and boric acid (17% B w/w) was used as source of boron for conducting

experiments.

3.1.3. Soil

Composite soil samples were collected before sowing of crop at depth of 0-30 cm

from different locations within the experimental field and working samples were made for

analysis of physico-chemical properties. The analysis was carried out at the Soil Fertility

Lab, Ayub Agricultural Research Institute, Faisalabad. Soil samples were air-dried, ground

and passed through a 2 mm sieve. Percentage of sand, silt and clay in the soil samples was

determined by the Bouyoucos hydrometer method (Moodie et al., 1959). Dispersion of 50

g soil sample was carried out in 1 L graduated cylinder using the distilled water and sodium

hexameta-phosphate. The textural class of soil was ascertained by using the International

Textural Triangle (Brady, 1990).

The soil samples were oven dried at 105 °C for 24 h to find out the soil moisture

percentage and it was followed by addition of distilled water to make the saturated paste.

The saturation percentage was calculated by dividing the total amount of water added (mL)

by the oven-dry weight of the soil (g) and multiplying by 100. Determination of soil pH

28

was carried out by the glass electrode method and electrical conductivity of the saturated

paste by the electrical conductivity method. The total soluble salts (TSS) were determined

by method of Richards (1954). The extractable and soluble Na in soil extracts was

determined by flame photometry and the exchangeable Na was calculated by the difference

between extractable and soluble Na (Estefan et al., 2013). The calcium carbonate (CaCO3)

was determined by the method of Allison and Moodie et al. (1965) and Page et al. (1982).

Total N was determined by the micro Kjeldhal method (Estefan et al., 2013), 0.5 M

NaHCO3 extracted P by the method of Olsen and Sommers (1982), exchangeable K by

flame photometric method and soil organic matter contents by the method of Ryan et al.

(2007), HCl-extractable B was determined by method of Ponnamperuma et al. (1981) and

DTPA - extractable Fe and Zn by the methods described by Baker and Amacher (1982).

The results of soil analyses are presented in Tables 3.1 and 3.2.

3.1.4. Meteorological data

The meteorological data during the both growing seasons of cotton crop (2014 and

2015) were collected from the Meteorological Observatory, Department of Crop

Physiology, University of Agriculture, Faisalabad and presented in Fig. 3.1.

3.1.5. Experimental treatments and design

A set of two field and two pot experiments was carried out to study the effect of

plant growth retardant (mepiquat chloride) and B on growth, allometry, phenology,

physiology, yield and quality of cotton. The field experiments were conducted during 2014

and 2015 using randomized complete block design (RCBD) with factorial arrangement

each replicated thrice. The net plot size was 6 m × 3 m. The layout for experiment 1 and 2

is given in Figures 3.2 and 3.3. The pot experiments were conducted during 2015 and 2016

using completely randomized design (CRD) with factorial arrangement and three

replications. The details of each experiment are given below.

3.2. Experiment 1: Influence of foliar applied mepiquat chloride and boron on growth,

productivity and earliness of cotton at different planting densities

This experiment was comprised of three factors i.e. planting density, foliar

application of mepiquat chloride and foliar application of B. The factors and their levels

that were included in this experiment are as follows;

Factor A (Planting density)

P1 = 53333 plants ha-1 (P × P = 25 cm)

P2 = 88888 plants ha-1 (P × P = 15 cm)

29

Factor B (Foliar application of mepiquat chloride)

M0 = Control (no mepiquat chloride)

M1 = 70 ppm mepiquat chloride solution at squaring

M2 = 70 ppm mepiquat chloride solution at flowering

Factor C (Foliar application of boron)

B0 = Control (no B)

B1 = 600 ppm B solution

B2 = 1200 ppm B solution

Foliar application of B solution was performed at five weeks after sowing, while,

mepiquat chloride was applied as per treatments when the crop was at squaring and

flowering stage. Water was sprayed in control. Calibration of spray volume was done using

water. Volume of spray used for mepiquat chloride application at squaring stage was 300

L ha-1 while for B and mepiquat chloride application at flowering stage was 350 L ha-1. The

spray was applied by using a Knapsack hand sprayer at a pressure of 207 kPa.

3.3. Experiment 2: Influence of foliar application of mepiquat chloride and soil

applied boron on growth, productivity and earliness of cotton

This experiment was comprised of two factors i.e. foliar application of mepiquat

chloride and soil applied B. The factors and their levels that were included in this

experiment are as follows;

Factor A (Foliar application of mepiquat chloride)

M0 = Control (no mepiquat chloride)

M1 = 70 ppm mepiquat chloride solution at squaring

M2 = 70 ppm mepiquat chloride solution at flowering

Factor B (Soil application of boron)

B0 = Control (no boron)

B1 = 1.0 kg B ha-1

B2 = 1.5 kg B ha-1

B3 = 2.0 kg B ha-1

B4 = 2.5 kg B ha-1

Boron was applied as basal dose, while, mepiquat chloride was applied when all the

plots had squaring and flowering as per treatments. Water was sprayed in control.

Calibration of spray volume was done using water. The volume of spray used for mepiquat

chloride application at squaring and flowering stage was 300 and 350 L ha -1, respectively.

The spray was applied by using a Knapsack hand sprayer at a pressure of 207 kPa.

30

Table 3.1: Soil physico-chemical properties for experiment 1

Year 2014 2015

Soil textural class Sandy loam

Organic matter (%) 0.96 0.99

Saturation (%) 28 27

pH 8.1 8.0

EC (dSm-1) 1.82 1.76

Total soluble salts (TSS) (mmol L-1) 19.02 18.21

Exchangeable sodium (mmol L-1) 9.40 9.10

CaCO3 (%) 5.23 5.09

Nitrogen (%) 0.048 0.050

Phosphorus (ppm) 7.3 6.9

Potassium (ppm) 255 259

Boron (ppm) 0.49 0.50

Zinc (ppm) 1.67 1.52

Iron (ppm) 5.31 5.13

31

Table 3.2: Soil physico-chemical properties for experiment 2

Year 2014 2015

Soil textural class Sandy loam

Organic matter (%) 1.02 0.97

Saturation (%) 28 28

pH 8.1 8.1

EC (dSm-1) 1.80 1.72

Total soluble salts (TSS) (mmol L-1) 18.30 17.80

Exchangeable sodium (mmol L-1) 8.90 8.8

CaCO3 (%) 5.21 5.12

Nitrogen (%) 0.051 0.049

Phosphorus (ppm) 7.1 6.9

Potassium (ppm) 260 246

Boron (ppm) 0.49 0.52

Zinc (ppm) 1.69 1.48

Iron (ppm) 5.21 5.10

32

Ra

infa

ll (

mm

), R

ela

tive h

um

idit

y (

%)

Max

. a

nd

Min

. T

em

pera

ture

(°C

)

2014

2015

Figure 3.1. Meteorological data during the course of present studies (Source: AgroMet Observatory, Department of Crop Physiology, UAF)

0

10

20

30

40

50

0

50

100

150

R.H. Rainfall Temp. Max. Temp. Min.

0

5

10

15

20

25

30

35

40

45

0

10

20

30

40

50

60

70

80

33

Figure 3.2: Layout for experiment 1

P1 = 53333 plants ha-1 (P × P = 25 cm); P2 = 88888 plants ha-1 (P × P = 15 cm); M0 = Control (no mepiquat chloride); M1 = 70 ppm mepiquat

chloride solution at squaring; M2 = 70 ppm mepiquat chloride solution at flowering; B0 = Control (no boron); B1 = 600 ppm boron solution;

B2 = 1200 ppm boron solution; R = Replication; NEA = Non-experimental area

Sub Water Channel

Mai

n W

ater

Ch

ann

el

R1

N.

E.

A.

P1

B2

M1

P2

B0

M0

P2

B2

M2

P1

B2

M0

P2

B1

M2

P1

B2

M2

P1

B1

M0

P2

B1

M0

P1

B0

M2

P1

B0

M0

P2

B2

M0

P2

B1

M1

P1

B0

M1

P2

B0

M1

P2

B2

M1

P1

B1

M2

P2

B0

M2

P1

B1

M1

N.

E.

A.

Central Path

R2

N.

E.

A.

P2

B1

M2

P2

B2

M1

P2

B0

M2

P1

B2

M1

P1

B1

M2

P2

B0

M0

P2

B1

M1

P1

B2

M2

P1

B0

M2

P2

B2

M0

P2

B2

M2

P1

B0

M1

P1

B1

M0

P1

B0

M0

P1

B2

M0

P2

B0

M1

P2

B1

M0

P1

B1

M1

N.

E.

A.

Sub Water Channel

R3

N.

E.

A.

P1

B0

M2

P2

B2

M0

P2

B1

M2

P2

B0

M0

P1

B0

M0

P2

B2

M1

P1

B1

M0

P1

B1

M2

P1

B0

M1

P1

B2

M2

P2

B0

M2

P2

B1

M0

P1

B2

M0

P1

B2

M1

P1

B1

M1

P2

B1

M1

P2

B2

M2

P2

B0

M1

N.

E.

A.

Main Path

34

Figure 3.3: Layout for experiment 2

M0 = Control (no mepiquat chloride); M1 = 70 ppm mepiquat chloride solution at squaring; M2 = 70 ppm mepiquat chloride solution at

flowering; B0 = Control (no boron); B1 = 1.0 kg boron ha-1; B2 = 1.5 kg boron ha-1; B3 = 2.0 kg boron ha-1; B4 = 2.5 kg boron ha-1; R =

Replication; NEA = Non-experimental area

Sub Water Channel

Mai

n W

ater

Ch

ann

el

R1

N

E

A

B0

M1

B0

M2

B2

M0

B1

M2

B1

M1

B0

M0

B2

M2

B2

M1

B1

M0

B3

M2

B4

M1

B3

M0

B3

M1

B4

M0

B4

M2

N

E

A

Central Path

R2

N

E

A

B4

M1

B3

M0

B2

M2

B2

M1

B4

M2

B0

M1

B0

M2

B2

M0

B3

M1

B4

M0

B1

M2

B1

M1

B0

M0

B1

M0

B3

M2

N

E

A

Sub Water Channel

R3

N

E

A

B1

M2

B1

M1

B3

M0

B2

M2

B2

M0

B3

M1

B4

M1

B0

M1

B1

M0

B2

M1

B4

M2

B4

M0

B3

M2

B0

M2

B0

M0

N

E

A

Main Path

35

3.4. Crop husbandry

3.4.1. Seedbed preparation

A soaking irrigation was applied a week before cotton planting to keep the experimental

land soft and moist to prepare root and seed bed. Seedbed was prepared by cultivating the field

for 3-4 times with tractor mounted cultivator each followed by planking. The beds were

prepared by using bed shaper.

3.4.2. Sowing

Cotton cultivar MNH-886 was sown on 26, May, 2014 and 22, May, 2015. The seed

was sown after delinting with commercial sulphuric acid (1:10 ratio) and treating with

fungicide (dynasty CST 125 FS @ 3 g kg-1 seed) before sowing. The crop was sown at beds

using dibbler by keeping the row to row distance of 75 cm and plant to plant distance was

varied as per treatment. At the time of sowing water was applied up to 15 cm depth of beds and

2-3 seeds were sown per hill about 2.5 cm above the water level. Seed rate of 25 and 15 kg ha-

1 was used for plant to plant distance of 15 and 25 cm, respectively. Thinning was done 25 days

after sowing (DAS) to maintain the plant populations as per treatments.

3.4.3. Fertilization

Recommended NPK fertilizers for cotton (200, 120 and 75 kg ha-1) were applied. All

P, K and 1/3 N was applied at sowing while remaining N was applied at squaring and boll

formation stages. Boron was applied according to the nature of treatments. The sources of

fertilizers used were urea (46% N), diammonium phosphate (18% N: 46% P2O5), sulfate of

potash (50% K2O) and boric acid (17% B).

3.4.4. Irrigation

First irrigation was applied 4 DAS and second irrigation was applied 7 days after first

irrigation. Subsequent irrigations were applied with an interval of 2 weeks according to the

crop and weather conditions. During 2014, eight irrigations were applied besides irrigation

applied at sowing, while, during 2015, five irrigations were applied due to occurrence of high

rainfall (Fig. 3.1).

3.4.5. Plant protection measures

Weeds were kept below economic threshold level by two hoeing (25 and 40 DAS) and

using non-selective herbicide (Glyphosate 48SL @ 1.5 L ha-1) at 55 DAS. Insect pests were

kept below economic threshold level through chemical control. During early vegetative growth

Acetamaprid 20 SL @ 625 g ha-1 was applied to control white fly (Bemisia tabaci). During

early squaring and flowering stages Imidacloprid was applied @ 625 mL ha-1 to control sucking

36

insects [Whitefly (B. tabaci), Jassid (Amrasca devastans) and Thrips (Thrips tabaci)].

Emamectin Benzoate 5% EC was applied @ 500 mL ha-1 during boll formation to control army

worm (Helicoverpa armigera).

3.4.6. Picking

The crop was harvested in two pickings carried out manually. First picking of seed

cotton was done when more than 60% bolls were opened during both the years. Second picking

was done on 9th November in 2014 and 12th November in 2015.

3.5. Procedures for recording data

3.5.1. Agronomic attributes of cotton

The plant growth and development monitoring and mapping was done by adopting the

procedures given by Kerby et al. (2010).

3.5.1.1. Plant height (cm)

Plant height of ten randomly selected plants from each plot was measured from

cotyledonary node of the plant to tip of main stem with the help of meter rod at the time of last

picking and then averaged.

3.5.1.2. Number of main stem nodes per plant

Number of nodes on main stem of ten randomly selected plants from each plot was

counted with cotyledonry node taking as zero and up to the plant terminal node having an

unfolded leaf (2.5 cm diameter) at last picking and then averaged.

3.5.1.3. Internodes length (cm)

The internodes length was calculated by using the following formula;

𝐼𝑛𝑡𝑒𝑟𝑛𝑑𝑒𝑠 𝑙𝑒𝑛𝑔ℎ𝑡 (𝑐𝑚) =𝑃𝑙𝑎𝑛𝑡 ℎ𝑒𝑖𝑔ℎ𝑡

𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑎𝑖𝑛 𝑠𝑡𝑒𝑚 𝑛𝑜𝑑𝑒𝑠

3.5.1.4. Number of monopodial branches

The monopodial branch is one that indirectly bears fruiting structures and arises on

node immediately below the node bearing sympodial branch. Ten plants were selected

randomly from each plot to count the number of monopodial branches and then their average

was calculated.

3.5.1.5. Number of sympodial branches per plant

The sympodial branch is one that directly bears fruiting structures. Total number of

sympodial branches of ten selected plants from each plot was counted at last picking and then

average number of sympodial branches per plant was calculated.

37

3.5.1.6. Node for first effective boll bearing (sympodial) branch

The number of main stem node for first effective sympodial branch (sympodial branch

with one or more retained bolls) of ten randomly selected plants from each plot was counted

with cotyledonry node taking as zero up to the sympodial branch that had a first position

retained boll and then averaged.

3.5.1.7. Number of nodes above white flower (NAWF)

The NAWF were counted 90 days after sowing from ten randomly selected plants from

each plot by counting the number of nodes on main stem from sympodial branch having a white

flower up to the terminal node with an unfolded leaf and then they were averaged.

3.5.1.8. Number of nodes above last cracked boll (NACB)

The NACB were counted from ten randomly selected plants from each plot by selecting

the uppermost first position cracked boll, then counting the number of main stem nodes

between the uppermost first-position cracked boll and the uppermost harvestable boll and

averaged. The NACB were counted when more than 60% of the plants from each plot had

opened bolls.

3.5.2. Phenological development of cotton

3.5.2.1. Number of days to first squaring (days)

Ten plants were selected and tagged randomly from each plot. On appearance of first

visible sized square with naked eye on 50% of selected plants, the number of days from planting

was recorded and then averaged.

3.5.2.2. Number of days to first flowering (days)

The number of days from sowing to the appearance of first flower on 50% of ten

selected plants was recorded in each replication and then they were averaged.

3.5.2.3. Number of days to first boll opening (days)

The ten tagged plants were observed from each plot. The number of days from sowing

to first boll opening of 50% of tagged were recorded and averaged.

3.5.2.4. Boll maturation period (days)

The boll maturation periods corresponds to the duration between appearance of flower

and boll opening. It was calculated by subtracting the number of days to first flower from

number of days to first boll opening for each replication.

3.5.2.5. Mean maturity days (days)

The mean maturity days (MMD) were calculated by using the procedure given by

Christidis and Harrison (1955), which is generalized as follows;

38

𝑀𝑀𝐷 = (𝑊1 − 𝐻1) + (𝑊2 − 𝐻2) + ⋯ + (𝑊𝑛 − 𝐻𝑛)

𝑊1 + 𝑊2 + ⋯ + 𝑊𝑛

where W = Weight of seed cotton, H = Number of days from planting to harvest 1, 2,..n =

Consecutive periodic harvest number

3.5.2.6. Earliness index (%)

Earliness index is the percent of first pick or harvest. This index is referred as maturity

coefficient. It was calculated for each replication using following formula;

𝐸𝑎𝑟𝑙𝑖𝑛𝑒𝑠𝑠 𝑖𝑛𝑑𝑒𝑥 (%) =𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑒𝑒𝑑 𝑐𝑜𝑡𝑡𝑜𝑛 𝑓𝑟𝑜𝑚 𝑓𝑖𝑟𝑠𝑡 𝑝𝑖𝑐𝑘 (𝑘𝑔 ℎ𝑎−1)

𝑇𝑜𝑡𝑎𝑙 𝑠𝑒𝑒𝑑 𝑐𝑜𝑡𝑡𝑜𝑛 𝑤𝑒𝑖𝑔ℎ𝑡 𝑓𝑟𝑜𝑚 𝑎𝑙𝑙 𝑝𝑖𝑐𝑘𝑠 (𝑘𝑔 ℎ𝑎−1)× 100

3.5.2.7. Production rate index (kg ha-1 day-1)

The production rate index for each replication was calculated by using following

formula;

𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 𝑖𝑛𝑑𝑒𝑥 (𝑘𝑔 ℎ𝑎−1𝑑𝑎𝑦 −1) =𝑇𝑜𝑡𝑎𝑙 𝑠𝑒𝑒𝑑 𝑐𝑜𝑡𝑡𝑜𝑛 𝑦𝑖𝑒𝑙𝑑 (𝑘𝑔 ℎ𝑎−1)

𝑀𝑒𝑎𝑛 𝑚𝑎𝑡𝑢𝑟𝑖𝑡𝑦 𝑑𝑎𝑦𝑠

3.5.2.8. Thermal time

Phenological development was also assessed on the basis of thermal time besides

calendar time as it has been suggested biologically more meaningful estimate of time required

for growth and development. The growing degree days (GDD) were accumulated from the

seeding date. Using a base temperature of 15.5 ºC, GDD were computed according to Jones

and Wells (1998);

𝐺𝐷𝐷 =∑(𝑇𝑚𝑎𝑥 + 𝑇𝑚𝑖𝑛)

2− 𝑇𝑏

where Tmax and Tmin denote daily maximum and minimum air temperatures (ºC), and Tb is the

base or threshold temperature below which physiological activities of rice are inhibited.

3.5.3. Allometric attributes of cotton

Two randomly selected plants were harvested leaving appropriate borders at 15 days

interval starting from 45 DAS. The above ground material at each harvest was dissected into

respective plant fractions (leaves, stem and reproductive structures). These were then used for

subsequent processing and measurements.

3.5.3.1. Leaf area (cm2)

An appropriate sub sample (5 g) of fresh green leaves was used to record leaf area using

laser leaf area meter (CI-203 Area meter CID, Inc). The leaf area of sub-samples was converted

into total leaf area per plant and expressed in cm2.

39

3.5.3.2. Dry matter production and its distribution (g plant -1)

Fresh and dry weights of component fractions of plants (leaves, stem, and reproductive

structures) were determined using an electronic balance. Due to the large biomass, a sub sample

of each fraction was taken and dried under sun for 48 hours followed by oven drying at 70°C

to a constant weight. The oven dry weight of sub samples of all the fractions was recorded,

converted to vegetative and reproductive dry weight per plant and expressed in grams per plant.

3.5.3.3. Total dry matter (g plant-1)

Total dry matter (TDM) was determined by summing the weight of all components per

plant and then converted to m-2. Total dry matter production was expressed in g m-2.

3.5.3.4. Reproductive-vegetative dry matter ratio

The reproductive-vegetative ratio (RVR) was calculated at 135 DAS by using the

following formula;

𝑅𝑉𝑅 = 𝐷𝑟𝑦 𝑚𝑎𝑡𝑡𝑒𝑟 𝑜𝑓 𝑟𝑒𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑣𝑒 𝑝𝑎𝑟𝑡𝑠 (𝑔)

𝐷𝑟𝑦 𝑚𝑎𝑡𝑡𝑒𝑟 𝑜𝑓 𝑣𝑒𝑔𝑒𝑡𝑎𝑡𝑖𝑣𝑒 𝑝𝑎𝑟𝑡𝑠 (𝑔)

3.5.3.5. Leaf area index

Leaf area index was calculated as the ratio of leaf area to land area as proposed by

Watson (1952);

𝐿𝐴𝐼 =𝐿𝑒𝑎𝑓 𝑎𝑟𝑒𝑎 𝑝𝑒𝑟 𝑝𝑙𝑎𝑛𝑡 (𝑐𝑚2)

𝐿𝑎𝑛𝑑 𝑎𝑟𝑒𝑎 𝑝𝑒𝑟 𝑝𝑙𝑎𝑛𝑡 (𝑐𝑚2)

3.5.3.6. Leaf area duration (days)

Leaf area duration (LAD) is an integral of LAI over the growth period and was

estimated according to Hunt (1978).

𝐿𝐴𝐷 (𝑑𝑎𝑦𝑠) =(𝐿𝐴𝐼2 − 𝐿𝐴𝐼1) × (𝑡2 − 𝑡1)

2

where LAI1 and LAI2 are leaf area indices at times t1 and t2, respectively. Cumulative LAD was

calculated by summing all the LAD values until maturity (LAD1 + LAD2 +....+ LADn).

3.5.3.7. Crop growth rate (g m-2 day-1)

Crop growth rate is defined as the dry matter accumulation per unit ground area per unit

time. It was calculated by using the method of Hunt (1978) and expressed as g m -2 day-1.

𝐶𝐺𝑅 (g 𝑚−2𝑑𝑎𝑦−1) =𝑊2 − 𝑊1

𝑡2 − 𝑡1

where W1 and W2 are the total dry weights at times t1 and t2, respectively. Mean CGR was

calculated by averaging all the CGR values.

40

3.5.3.8. Net assimilation rate (g m-2 day-1)

Net assimilation rate of a plant is the increase in dry matter per unit assimilatory area

per unit time. The NAR was calculated by using the formula of Hunt (1978);

𝑁𝐴𝑅 (𝑔 𝑚−2𝑑𝑎𝑦−1) =𝑇𝐷𝑀

𝐿𝐴𝐷

where TDM = total dry matter (g m-2) and LAD = leaf area duration. Mean NAR was calculated

by averaging all the NAR values.

3.5.4. Boll distribution pattern of cotton

3.5.4.1. Proportion of bolls at first position (%)

The number of bolls at first sympodial positions were counted from ten tagged plants

from each plot and then averaged. The proportion of bolls at first sympodial positions was

calculated by using the following formula;

𝐹𝑖𝑟𝑠𝑡 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛 𝑏𝑜𝑙𝑙𝑠 (%) =𝑁𝑜. 𝑜𝑓 𝑏𝑜𝑙𝑙𝑠 𝑎𝑡 𝑓𝑖𝑟𝑠𝑡 𝑠𝑦𝑚𝑝𝑜𝑑𝑖𝑎𝑙 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛𝑠

𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑏𝑜𝑙𝑙𝑠× 100

3.5.4.2. Proportion of bolls at second position (%)

The number of bolls at second sympodial positions were counted from ten tagged plants

from each plot and then averaged. The proportion of bolls at second sympodial positions was

calculated by using the following formula;

𝑆𝑒𝑐𝑜𝑛𝑑 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛 𝑏𝑜𝑙𝑙𝑠 (%) =𝑁𝑜. 𝑜𝑓 𝑏𝑜𝑙𝑙𝑠 𝑎𝑡 𝑠𝑒𝑐𝑜𝑛𝑑 𝑠𝑦𝑚𝑝𝑜𝑑𝑖𝑎𝑙 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛𝑠


3.5.4.3. Proportion of bolls at outer position (%)

The number of bolls on sympodial branches after the second position were counted

from ten tagged plants from each plot and then averaged. The proportion of bolls at outer

sympodial positions was calculated by using the following formula;

𝑂𝑢𝑡𝑒𝑟 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛 𝑏𝑜𝑙𝑙𝑠 (%) =𝑁𝑜. 𝑜𝑓 𝑏𝑜𝑙𝑙𝑠 𝑎𝑡 𝑜𝑢𝑡𝑒𝑟 𝑠𝑦𝑚𝑝𝑜𝑑𝑖𝑎𝑙 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛𝑠


where, the outer position bolls corresponds to the total number of bolls at third as well as farther

positions.

3.5.5. Yield and related attributes of cotton

3.5.5.1. Plant population

The total number of plants from each plot was counted at harvest and converted to

number of plants m-2.

41

3.5.5.2. Number of unopened bolls per plant

The number of unopened bolls per plant was counted at second picking from ten

randomly selected tagged plants from each plot and then averaged.

3.5.5.3. Number of opened bolls per plant

The number of opened bolls per plant was counted at first and second picking from ten

randomly selected tagged plants from each plot and then averaged after summing the number

of opened bolls at bot pickings.

3.5.5.4. Boll density

Number of opened bolls per plant were converted to number of opened bolls m-2 to

calculate the boll density.

3.5.5.5. Total number of bolls per plant

Total number of bolls were calculated by summing the opened and unopened boll from

ten selected plants from each plot and then they were averaged.

3.5.5.6. Boll weight (g)

Twenty bolls were picked from each plot and weighed with the help of electric weighing

balance followed by averaging.

3.5.5.7. Number of seeds per boll

Seeds obtained from twenty bolls from each plot were counted after ginning and

averaged to determine the number of seeds per bolls.

3.5.5.8. Seed index (g)

Seed index were determined by weighing the hundred fuzzy seeds in grams.

3.5.5.9. Seed cotton yield (kg ha-1)

Cotton was picked from the plants in the net plot area and weighed. The yield obtained

from twenty bolls from each plot was also added to this. The yield per hectare was worked out

based on net plot yield obtained from all pickings.

3.5.5.10. Lint yield (kg ha-1)

The lint yield was calculated by using the following formula;

𝐿𝑖𝑛𝑡 𝑦𝑖𝑒𝑙𝑑 (𝑘𝑔 ℎ𝑎−1) =𝑆𝑒𝑒𝑑 𝑐𝑜𝑡𝑡𝑜𝑛 𝑦𝑖𝑒𝑙𝑑 (𝑘𝑔 ℎ𝑎−1) × 𝐿𝑖𝑛𝑡 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒

100

3.5.5.11. Cotton seed yield (kg ha-1)

The cotton seed yield was calculated by subtracting the lint yield from seed cotton yield

and expressed in kg ha-1.

42

3.5.6. Fiber quality attributes of cotton

3.5.6.1. Ginning out turn (%)

The seed cotton obtained from all pickings was mixed thoroughly from each

replication. A composite sample was taken from this composited harvest, dried in sun and

cleaned by removing the inert matter. The clean and dry samples of seed cotton were weighed

and ginned separately with a single roller electric gin. The lint obtained from each sample was

weighed and its ginning out turn (GOT) was calculated by using following formula;

𝐺𝑂𝑇 (%) =𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑙𝑖𝑛𝑡 (𝑔)

𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑒𝑒𝑑 𝑐𝑜𝑡𝑡𝑜𝑛 (𝑔)× 100

After ginning, 15 g lint samples from each replication were taken and sent to

Department of Fiber and Textile Technology, University of Agriculture, Faisalabad to

determine the physical properties of fiber (fiber length, micronaire, fiber strength, fiber

uniformity ratio and fiber maturity) using high volume instrument analysis (HVI-900

Zellwegar Uster Ltd., Switzerland). The procedures were adopted as described by ASTM

standard (1997).

3.5.6.2. Fiber length (mm)

The fiber length is usually considered as the length at 2.5% span length. HVI-900

length/strength module measures the length at 2.5% span length and 50% span length through

optical system. The 2.5% span length was measured and expressed in mm.

3.5.6.3. Micronaire (µg inch-1)

The fiber fineness is the measure of fiber weight in µg per unit length of fiber. When

the air steam is passed through known mass of fiber confined in the chamber of fixed volume

of module-920, the pressure difference across the chamber helps to determine micronaire value.

The micronaire was measured and expressed in µg inch-1.

3.5.6.4. Fiber strength (g tex-1)

The fiber strength is ratio of breaking strength of a bundle of fiber to its weight. The

length/strength module-920 of HVI-900 measures the fiber strength by principle of contrast

rate of force application on the clamped fiber of the sample taken for fiber length

measurements. The fiber strength was measured and expressed in g tex-1.

3.5.6.5. Fiber uniformity ratio (%)

The length/strength module-920 of HVI-900 measured the 50% and 2.5% span length

and the fiber length uniformity ratio was calculated using following formula and expressed in

percentage;

43

𝐹𝑖𝑏𝑒𝑟 𝑢𝑛𝑖𝑓𝑜𝑟𝑚𝑖𝑡𝑦 𝑟𝑎𝑡𝑖𝑜 =50% 𝑠𝑝𝑎𝑛 𝑙𝑒𝑛𝑔𝑡ℎ (𝑚𝑚)

2.5% 𝑠𝑝𝑎𝑛 𝑙𝑒𝑛𝑔𝑡ℎ (𝑚𝑚)× 100

3.5.6.6. Fiber maturity (%)

This represents the ratio of the matured, half matured and immature fibers in a sample

of lint. The fiber maturity was measured and expressed in percentage.

3.5.7. Plant analysis

3.5.7.1. Photosynthetic pigments of cotton (mg g-1)

Chlorophyll contents (Chl) were determined by methods of Arnon (1949) and Davies

(1976). Fully expanded young leaf blade usually the upper most 4 th leaf (0.5 g) samples of

cotton from each replication were collected randomly during active boll development stage (80

DAS) and soaked in 80% acetone overnight. Absorbance readings (480, 645 and 663 nm) of

supernatant were recorded using spectrophotometer and calculations of chlorophyll and total

carotenoids contents were done by using the following formulae;

𝐶ℎ𝑙 𝑎 (𝑚𝑔 𝑔−1) = [{(0.0127 × 𝐴663) − (0.00269 × 𝐴645) × 𝑉}/𝑊]

𝐶ℎ𝑙 𝑏 (𝑚𝑔 𝑔−1 ) = [{(0.0229 × 𝐴645) − (0.00468 × 𝐴663) × 𝑉}/𝑊]

𝑇𝑜𝑡𝑎𝑙 𝐶ℎ𝑙 (𝑚𝑔 𝑔−1) = [{(0.0202 × 𝐴645) + (0.00802 × 𝐴663) × 𝑉}/𝑊]

𝑇𝑜𝑡𝑎𝑙 𝑐𝑎𝑟𝑜𝑡𝑒𝑛𝑜𝑖𝑑𝑠 (𝑚𝑔 𝑔−1) = (𝐴𝑐𝑎𝑟/𝐸𝑀) × 100

where, A = absorbance, V = volume of sample extract, W = weight of sample, EM = 2500

and 𝐴𝑐𝑎𝑟 = [{A480 + (0.114 × A663) − (0.638 × A645) × V}/𝑊]. The Chl a/b ratio was

calculated by dividing the Chl a by Chl b.

3.5.7.2. Tissue nutrient contents of cotton

3.5.7.2.1. Sampling and sample preparation

The leaves and seed samples from each replication were assayed to determine the

contents of N, P, K, B, Zn, Mn and Fe. For this purpose, fully expanded young leaf blades

usually uppermost 4th leaf samples were collected randomly during active boll development

stage (80 DAS) and seeds were collected after ginning. The seeds were delinted with

commercial sulfuric acid (1:10 ratio) followed by washing for 2-3 times with water and

drying under sun and electric oven at 70 °C for 24 h. Then the leaves and seeds were ground

to powder form (Cyclotec 1093 Sample Mill, Sweden) to pass through a 30-mesh screen and

stored in plastic envelopes for carrying out analysis. The details of nutrients analysis is given

below.

3.5.7.2.2. Nitrogen (mg g-1 DW)

The concentration of N in cotton leaves and seeds from each replication was determined

44

by Kjeldahl method as described by Estefan et al. (2013).

i) Digestion

Dry ground leaves and seeds samples of the size of 0.5 g were weighed and transferred

in 100 mL Pyrex digestion tubes. It was followed by addition of catalyst mixture

[K2SO4:CuSO4.5H2O 10:1 w/w ratio] and 10 mL of concentrated sulfuric acid (98%,

sp.gr.1.84) and stirred with Vortex tube stirrer until mixed well. Tubes were placed in a block-

digester set at 100 °C for 20 minutes, and then tubes were removed to wash down any material

adhering to the neck of the tube with the same concentrated H2SO4. Then the tubes were place

back on the block-digester set at 380 °C for 2 hours until clearing of material. Digestion tubes

were removed; cooled and volume was made up to 100 mL with distilled water after digestion

was complete. Each batch of samples for digestion contained at least one reagent blank (no

plant).

ii) Distillation

Distillation was carried out by dispensing the 1 mL of saturated H3BO3 solution and 1

mL of distilled water in a 100 mL Pyrex evaporating dish. The dish was placed under the

condenser tip and tip was touching the solution. It was followed by addition of 10 mL aliquot

and 10 mL of 10 N solution of NaOH in a 100 mL distillation flask. The flask was immediately

connected to distillation unit and distillation was started.

iii) Titration

An auto Titrator was used to titrate the distillate to pH 5 against 0.01 N H2SO4 and

the volume of the acid was recorded.

iv) Nitrogen concentration

The concentration of nitrogen was determined by using the following formula and

converted to mg g-1 of dry weight;

𝑁(%) =(𝑉1 − 𝐵) × 𝑁 × 𝑉2 × 14.01 × 100

𝑊 × 𝑉3 × 1000

where, V1 = Volume of 0.01 N H2SO4 used for sample titration (mL); V2 = Total volume of

digested sample (mL); V3 = Volume of digested sample utilized for distillation (mL); B=

Volume of digested blank titration (mL); W = Dry weight of plant sample (g); 14.01 = Atomic

weight of nitrogen

3.5.7.2.3. Phosphorus (mg g-1 DW)

The concentration of P in cotton leaves and seeds from each replication was determined

colorimetrically by method described by Estefan et al. (2013).

45

i) Digestion

The cotton leaves and seeds samples were digested using sulfuric acid and catalyst as

described for nitrogen determination in section 3.0.0.0.

ii) Phosphorus concentration

Ammonium-vanadomolybdate reagent was prepared by dissolving 22.5 g ammonium

heptamolybdate in 400 mL distilled water, 1.25 g ammonium metavanadate in 300 mL hot

distilled water, mixing both the solutions, adding 250 mL concentrated nitric acid to the mixture

and bringing the volume up to 1 L by distilled water. 10 mL of clear filtrate after digestion was

pipetted into a 100-mL flask.Then10 mL of ammonium-vanadomolybdate reagent was added

to the filtrate and the solution was diluted to volume with distilled water. A standard curve was

prepared by pipetting 10 ml of 0.5, 1.0, 1.5, 2.0 and 2.5 ppm of standard solutions and

proceeding as for the samples. Then a blank with 10 mL ammonium-vanadomolybdate reagent

was prepared and proceeded as for the samples. Absorbance of the blank, standards, and

samples was read after 30 minutes on the spectrophotometer at 410 nm wavelength. Calibration

curve for standards was prepared by plotting absorbance against the respective P

concentrations. Concentration of P in the unknown samples was read from the calibration

curve. The concentration of P in samples was calculated using the following formula;

𝑃 (𝑚𝑔 𝑔−1) = 𝑝𝑝𝑚 𝑃 (𝑓𝑟𝑜𝑚 𝑐𝑢𝑟𝑣𝑒) ×𝑉1

𝑊×

100

𝑉2

×1

10

where, V1 = total volume of the plant digest (mL), V2 = volume of plant digest used for

measurement (mL), W= weight of dry plant (g)

3.5.7.2.4. Potassium (mg g-1 DW)

The concentration of K in cotton leaves and seeds was determined by following the

procedure of Estefan et al. (2013).

i) Digestion

One gram dry ground leaves and seeds samples was weighed and transferred in 100 mL

Pyrex digestion tubes and 10 mL di-acid mixture [nitric acid and perchloric acid (2:1) on

volume basis] were added into digestion tubes and kept overnight. Next day, digestion tubes

were placed on cold block-digester and heated first at 150 °C for 1 h then temperature was

raised up to 235 °C and digested till the fumes of nitric acid and perchloric acid disappeared

and the solution was colorless. The tubes were cooled; few drops of distilled water were added

and waited for the fumes to be condensed. The solution was transferred to volumetric flask and

46

made the volume up to 100 mL with distilled water. Each batch of samples for digestion

contained one reagent blank (no plant material).

ii) K+ concentration

The digested samples of leaves and seeds were fed to the flame photometer for the

determination of K ion. The instrument was standardized using a series of K standard solutions

(2, 4, 6, 8, 10, 15 ppm). Then a standard curve was prepared by plotting concentration on x-

axis and instrument reading on y- axis. Potassium ion concentration in supernatant liquid was

calculated from the calibration curve using the following formula;

𝐾 (𝑚𝑔 𝑔−1) =𝑝𝑝𝑚 𝐾 (𝑓𝑟𝑜𝑚 𝑐𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝑐𝑢𝑟𝑣𝑒) × 𝑉

𝑊 × 1000

where, V = total volume of the plant digest (mL) and W = weight of dry plant (g)

3.5.7.2.5. Boron (µg g-1 DW)

Samples for leaves and cotton seed B contents were prepared by dry ashing (Chapman

and Pratt, 1961). One gram of ground tissue was placed in a porcelain crucible for ashing at

550°C for 6 h. The ashed samples were then extracted with 10 mL of 0.36 N H2SO4 for 1 h and

after filtration the samples were transferred in plastic vials and 50 mL final volume was made

up by using distilled water. Then 2 mL of the solution was added to the 4 mL of buffer solution

(containing 25% ammonium acetate, 1.5% EDTA and 12.5% acetic acid) and 4 mL of

azomethine-H solution containing 0.45% azomethine-H and 1% of ascorbic acid prepared right

before the analysis. The samples were left to develop color for at least 30 min. A standard curve

was prepared by preparing B standard solutions (0.5-3.0 ppm) using boric acid and a blank

sample with 1 mL distilled water and proceeded as for samples. The absorbance reading of

samples, blank and standard solutions was taken at 420 nm by using a spectrophotometer and

the concentration of B in samples was determined from the calibration curve (Bingham, 1982;

Ho et al., 1986; Malekani and Cresser, 1998). The concentration of B was calculated using the

following formula;

𝐵 (𝑝𝑝𝑚) =𝑝𝑝𝑚 𝐵 (𝑓𝑟𝑜𝑚 𝑐𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝑐𝑢𝑟𝑣𝑒) × 𝑉

𝑊


3.5.7.2.6. Zinc (µg g-1 DW)

Concentration of Zn in leaves and seeds samples of cotton were estimated by the

method of Estefan et al. (2013). Di-acid digestion was carried as described in section 3.0.0.0.

Standards of Zn (0.2, 0.4, 0.8, 1.0 and 1.2 ppm) were prepared by using ZnSO4. Standard curve

was drawn by running the series of standard solutions. The supernatant liquid of samples was

47

decanted to analyze Zn concentration in the aliquots by atomic absorption spectrophotometer.

The supernatant liquid concentrations were calculated according to the calibration curve.

𝑍𝑛 (µ𝑔 𝑔−1) =𝑝𝑝𝑚 𝑍𝑛 (𝑓𝑟𝑜𝑚 𝑐𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝑐𝑢𝑟𝑣𝑒) × 𝑉

𝑊


3.5.7.2.7. Manganese (µg g-1 DW)

The concentration of Mn in cotton leaves and seeds samples were estimated by the


Standards of Mn (0.2, 0.4, 0.8, 1.0 and 1.2 ppm) were prepared by using MnCl2. Standard curve


decanted to analyze Mn concentration in the aliquots by atomic absorption spectrophotometer.


𝑀𝑛 (µ𝑔 𝑔−1) =𝑝𝑝𝑚 𝑀𝑛 (𝑓𝑟𝑜𝑚 𝑐𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝑐𝑢𝑟𝑣𝑒) × 𝑉

𝑊


3.5.7.2.8. Iron (µg g-1 DW)

The concentration of Fe in cotton leaves and seeds samples were estimated by the


Standards of Fe (0.2, 0.4, 0.8, 1.0 and 1.2 ppm) were prepared by using FeSO4. Standard curve


decanted to analyze Fe concentration in the aliquots by atomic absorption spectrophotometer.


𝐹𝑒 (µ𝑔 𝑔−1) =𝑝𝑝𝑚 𝐹𝑒 (𝑓𝑟𝑜𝑚 𝑐𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝑐𝑢𝑟𝑣𝑒) × 𝑉

𝑊


3.5.7.3. Seed protein content (%)

Protein content was assayed by determining the N content in seed samples by Kjeldhal

method and calculated by using the formula of AOAC (1990);

𝑆𝑒𝑒𝑑 𝑝𝑟𝑜𝑡𝑒𝑖𝑛 (%) = 𝑁(%) × 6.25

3.5.7.4. Seed protein yield (kg ha-1)

Seed protein yield was calculated by using the following formula and expressed in kg

ha-1;

𝑆𝑒𝑒𝑑 𝑝𝑟𝑜𝑡𝑒𝑖𝑛 𝑦𝑖𝑒𝑙𝑑 (𝑘𝑔 𝑘𝑔−1) =𝑆𝑒𝑒𝑑 𝑝𝑟𝑜𝑡𝑒𝑖𝑛 (%) × 𝐶𝑜𝑡𝑡𝑜𝑛 𝑠𝑒𝑒𝑑 𝑦𝑖𝑒𝑙𝑑 (𝑘𝑔 ℎ𝑎−1)

100

48

3.5.7.5. Seed oil content (%)

Seed oil content was determined by following the procedure of AOAC (1990). A 3 g of

oven dried ground cotton seed sample was weighed (W1) and wrapped in filter paper. The

wrapped sample was put in extraction tube of Soxhlet’s apparatus along with petroleum ether.

The petroleum ether was continued to pour in extraction tube until it siphoned in the flask of

Soxhlet’s apparatus. Then the water and heater was turned on to start extraction of oil. After 6-

7 siphoning the petroleum ether was allowed to accumulate in extraction tube while flask was

disconnected. The ether remained in the extraction tube was recovered for future use. The

material (oil + ether) in the flask was collected in a weighed petri dish (W2). The petri dish was

placed in an electric oven at 100 °C for 30 minutes after which the petri dish containing oil was

removed from oven, cooled and weighed (W3). The oil percentage was calculated using the

following formula;

𝑂𝑖𝑙 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 (%) = (𝑊3 − 𝑊2

𝑊1

) × 100

3.5.7.6. Seed oil yield (kg ha-1)

The seed oil yield was calculated by using the following formula and expressed in kg

ha-1;

𝑆𝑒𝑒𝑑 𝑜𝑖𝑙 𝑦𝑖𝑒𝑙𝑑 (𝑘𝑔 𝑘𝑔−1) =𝑆𝑒𝑒𝑑 𝑜𝑖𝑙 (%) × 𝐶𝑜𝑡𝑡𝑜𝑛 𝑠𝑒𝑒𝑑 𝑦𝑖𝑒𝑙𝑑 (𝑘𝑔 ℎ𝑎−1)

100

3.5.7.7. Seed ash content (%)

Cotton seed ash content was determined by taking 1 g of well ground sample and it was

placed in clean and already weighed china crucible. The samples were burnt on flame and

placed into muffle furnace at 550 °C for 4 hours, cooled in desiccator and weighed. The ash

content was determined by formula as described in AOAC (1990).

𝐴𝑠ℎ (%) = (𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒 𝑎𝑛𝑑 𝑎𝑠ℎ (𝑔) − 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒(𝑔)

𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 (𝑔)) × 100

3.5.8. Nutrient use efficiency

Nutrient use efficiency of boron was calculated according to Dordas (2006a) using the

following formula;

𝑁𝑈𝐸 =𝑆𝑒𝑒𝑑 𝑐𝑜𝑡𝑡𝑜𝑛 𝑦𝑖𝑒𝑙𝑑 𝑤𝑖𝑡ℎ 𝑏𝑜𝑟𝑜𝑛 𝑎𝑝𝑝𝑙𝑖𝑐𝑎𝑡𝑖𝑜𝑛

𝑆𝑒𝑒𝑑 𝑐𝑜𝑡𝑡𝑜𝑛 𝑦𝑖𝑒𝑙𝑑 𝑤𝑖𝑡ℎ𝑜𝑢𝑡 𝑏𝑜𝑟𝑜𝑛 𝑎𝑝𝑝𝑙𝑖𝑐𝑎𝑡𝑖𝑜𝑛

49

3.5.9. Critical concentration of boron

Critical concentration of B was determined by plotting the graph between the relative

seed cotton yield (95%) vs. B concentration (%) in the corresponding leaf tissue by Boundary

Line Technique (Webb, 1972).

3.5.10. Boron fertilizer requirement of cotton

The B fertilizer requirement of cotton crop was determined by plotting the graph

between the relative seed cotton yield (95%) vs. foliar as well as soil applied B by Boundary

Line Technique (Webb, 1972).

3.6. Soil bioassay: Influence of previously treated cotton crop with mepiquat chloride and

boron on emergence and seedling growth of progeny

Seed obtained from experiment 1 and 2 during both years was used for the

determination of effect of maternal treatment with mepiquat chloride and B on seed quality in

terms of emergence and progeny seedling growth of cotton. The experiments were conducted

by sowing ten seeds in soil filled pots in first week of April during both years (2015 and 2016)

for bioassay studies. At the start 100 mL of water was applied to each pot and then according

to the requirement. The experiments were observed for 21 days. The maximum and minimum

temperature was recorded during the experimental period and averaged. The average maximum

temperature was 31.1 and 33.0 °C, and minimum temperature was 19.3 and 19.7 °C in 2015

and 2016, respectively.

3.7. Procedures for data recording

3.7.1. Emergence

3.7.1.1. Final emergence percentage (%)

Data regarding the number of seedlings emerged were noted daily up to the end of

experiment as per method of Association of Official Seed Analysts (1990). Emergence

percentage was calculated by using following formula for each replication of a treatment at

the end of the experiment after cessation of emergence.

Final emergence percentage (%) = No. of seedlings emerged

Total number of seeds×100

3.7.1.2. Emergence index

The emergence index was calculated as per Association of Official Seed Analysts

(1983) by using the following formula;

Emergence index = 𝑁𝑜. 𝑜𝑓 𝑒𝑚𝑒𝑟𝑔𝑒𝑑 𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔𝑠

𝐷𝑎𝑦𝑠 𝑜𝑓 𝑓𝑖𝑟𝑠𝑡 𝑐𝑜𝑢𝑛𝑡 + − − +

𝑁𝑜. 𝑜𝑓 𝑒𝑚𝑒𝑟𝑔𝑒𝑑 𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔𝑠

𝐷𝑎𝑦𝑠 𝑜𝑓 𝑓𝑖𝑛𝑎𝑙 𝑐𝑜𝑢𝑛𝑡

50

3.7.1.3. Mean emergence time (days)

Equation of Ellis and Roberts (1981) was used to calculate the mean emergence time;

Mean emergence time (days) = ∑𝐷𝑛

𝑁

where, n is the number of emerged seedlings on day D and N is the total number of

germinated/emerged seeds.

3.7.2. Seedling growth

3.7.2.1. Root length of seedling (cm)

Root length of all the seedlings from each replication was measured at the end of

experiment using measuring scale and expressed in cm. Root length was measured from the

point where root and shoot joins together to the end of root. Then average root length was

calculated.

3.7.2.2. Shoot length of seedling (cm)

Shoot length of all the seedlings from each replication was measured at the end of

experiment using scale and expressed in cm. Shoot length was measured from the point where

root and shoot joins together to the end of shoot. Then average shoot length was calculated.

3.7.2.3. Root fresh weight (mg)

Roots were isolated from all the seedlings from each replication and weighed with an

electric weighing balance. The weight was expressed in mg. Afterwards, the average root

fresh weight per seedling was calculated.

3.7.2.4. Shoot fresh weight (mg)

Shoots were isolated from all the seedlings and weighed with an electric weighing

balance. The weight was expressed in mg. Then average shoot fresh weight per seedling was

determined.

3.7.2.5. Root dry weight (mg)

All the detached roots were oven dried at 70o C till constant weight. The average root

dry weight per seedling in mg was calculated.

3.7.2.6. Shoot dry weight (mg)

Separated shoots of all seedlings from each replication were oven dried at 70o C till

constant weight. The average shoot dry weight per plant in mg was calculated.

3.7.2.7. Seedling vigor index

Seedling vigor index was calculated according to the equation of Abdul-Baki and

Anderson (1973);

51

𝑆𝑒𝑒𝑑𝑙𝑖𝑛𝑔 𝑣𝑖𝑔𝑜𝑢𝑟 𝑖𝑛𝑑𝑒𝑥 = 𝐸𝑚𝑒𝑟𝑔𝑒𝑛𝑐𝑒 (%) × 𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔 𝑙𝑒𝑛𝑔𝑡ℎ (𝑐𝑚)

The seedling length was calculated by summing the root length and shoot length.

3.8. Economic analysis

Economic analysis was performed on the basis of variable costs of treatments. The cost

of production of cotton during 2014 and 2015 was calculated for factors which were kept

uniform such as seedbed preparation, sowing, fertilizer, irrigation, plant protection measures

etc. Variable cost incurring on different treatments of B, mepiquat chloride and different

planting densities was calculated separately. The gross income for each treatment was

calculated on the basis of seed cotton yield per hectare according to present market value. Net

field benefit was calculated by subtracting the total variable cost from the total benefits of each

treatment combination. Input and output cost for each treatment combination was converted

into Rs. ha-1. The benefit cost ratio (BCR) for all individual treatments was calculated by using

the following formula (CIMMYT 1988);

BCR =Gross income

Total cost

Net field benefits were calculated by subtracting the variable cost from gross income.

Marginal rate of return (MRR) was calculated by using the following formula (CIMMYT

1988);

𝑀𝑅𝑅 (%) =𝑀𝑎𝑟𝑔𝑖𝑛𝑎𝑙 𝑛𝑒𝑡 𝑏𝑒𝑛𝑒𝑓𝑖𝑡𝑠

𝑀𝑎𝑟𝑔𝑖𝑛𝑎𝑙 𝑐𝑜𝑠𝑡 × 100

3.9. Statistical analysis

The data were analyzed by using the Fisher’s analysis of variance technique (Steel et

al., 1997) using Statistix 8.1 (Analytical software, Statistix; Tallahassee, FL, USA, 1985-2003)

and treatments’ means were compared by using the honest significance difference (HSD)

Tukey’s test at 5% probability. The relationship among different variables was ascertained by

regression and correlation analysis that was performed by using MS-Excel 2013.

52

CHAPTER 4

RESULTS AND DISCUSSION

4.1. Influence of foliar applied mepiquat chloride and boron at different planting densities

4.1.1. Plant growth and architecture

Plant growth and architectural attributes varied significantly by the influence of foliar

applied B and mepiquat chloride, and planting density, during both years (Tables 4.1, 4.2). The

interaction of B with mepiquat chloride was non-significant for plant height, number of main

stem nodes, internodes length, number of monopodial and sympodial branches, and node for

first effective sympodial branch, while, significant for NAWF and NACB, during both years

(Tables 4.1, 4.2). However, the interactions of mepiquat chloride with planting density, B with

planting density and three way interaction among B, mepiquat chloride and planting density

was non-significant for all the growth and architectural attributes, during both years (Tables

4.1, 4.2).

Plant height was increased by foliage applied B (11-13%) while decreased by mepiquat

chloride application (13-14%), as compared to control. Tallest plants were recorded by

application of 1200 ppm B; however, the effect of 600 ppm B solution on plant height was

statistically similar during 2014. Smallest plants were produced by mepiquat chloride

application at squaring stage, during both years (Tables 4.3a, 4.4a). Sowing the cotton at higher

planting density resulted in an increase in plant height by 9-10%, as compared to lower planting

density, during both years (Tables 4.3b, 4.4b). The number of main stem nodes were increased

by foliage applied B (5%) and decreased by mepiquat chloride application (7%). Treatment

with 1200 ppm B caused maximum increase in number of main stem nodes while effect of 600

ppm B solution was at statistically par, during both years (Tables 4.5a, 4.6a). The mepiquat

chloride application at squaring stage caused maximum decrease in number of main stem nodes

and it was followed by mepiquat chloride application at flowering stage (Tables 4.5a, 4.6a).

The number of main stem nodes were lower at higher planting density (7%), as compared to

lower planting density (Tables 4.5b, 4.6b). Application of B enhanced the internodes length

with maximum increase (6-7%) occurring by spraying the 1200 ppm B solution during both

years, while, similar effect was produced by 600 ppm B during 2014 (Tables 4.7a, 4.8a).

However, mepiquat chloride decreased the internodes length (7-8%), as compared to control

during both years. Mepiquat chloride application at squaring stage produced shortest internodes

53

during both years (Tables 4.7a, 4.8a). The internodes length of cotton plants was higher at

higher planting density (17-19%), as compared to lower planting density during both years

(Tables 4.7b, 4.8b).

Number of monopodial branches were increased by B application (7-8%) and decreased

by mepiquat chloride (13-14%), as compared to control, during both years. The highest number

of monopodial branches was recorded by treatment with 1200 ppm B while the effect of 600

ppm B solution was statistically similar (Tables 4.9a, 4.10a). Mepiquat chloride application at

squaring stage decreased the number of monopodial branches to a maximum, during both years

(Tables 4.9a, 4.10a). Likewise, the monopodial branches were decreased (5-7%) at higher

planting density, as compared to lower planting density (Tables 4.9b, 4.10b). The number of

sympodial branches was increased by boron application (6-7%) with maximum number of

sympodial branches produced by 1200 ppm B. However, the effect of 600 B boron solution on

number of sympodial branches was statistically similar, during both years (Tables 4.11a,

4.12b). On the other hand, spraying the mepiquat chloride decreased the number of sympodial

branches (8%) and application of mepiquat chloride at squaring stage caused maximum

decrease. The effect of mepiquat chloride treatment at flowering stage on number of sympodial

branches was statistically similar, during 2014 (Tables 4.11a, 4.12a). Similarly, lesser

sympodial branches (9-10%) were recorded at higher planting density, as compared to lower

planting density, during both years (Tables 4.11b, 4.12b).

Foliar applied B and mepiquat chloride caused a reduction in node for first effective

sympodial branch, as compared to control, during both years, though did not interacted with

each other. Maximum reduction (4-9%) was caused by application of 1200 ppm B and it was

followed by the effect of 600 ppm B (Tables 4.13a, 4.14a). Mepiquat chloride application at

squaring stage caused greatest decrease in node for first effective sympodial branch (5-20%),

during both years, while the effect of mepiquat chloride application at flowering stage was

statistically similar during 2014 (Tables 4.13a, 4.14a). Likewise, increasing the planting

density lead to a reduction in node for first effective sympodial branch (3-6%), during both

years (Tables 4.13b, 4.14b). The NAWF were decreased by application of B and mepiquat

chloride across planting densities as compared to control, during both years. Maximum

decrease in NAWF (26-32%) was noticed by application of 1200 ppm B solution in

combination with mepiquat chloride application at squaring stage, during both years (Tables

4.15a, 4.16a). In case of planting density, a decrease in NAWF (6-9%) was recorded by sowing

the crop at higher planting density, during both years (Tables 4.15b, 4.16b). Application of B

54

Table 4.1: Analysis of variance for influence of foliar applied mepiquat chloride and boron at various planting densities on agronomic


DF: Degree of freedom; ns: Non-significant; *: Significant at p 0.05; **: significant at p 0.01

Table 4.2: Analysis of variance for influence of foliar applied mepiquat chloride and boron at various planting densities on agronomic



Source of variation DF

Mean sum of squares

Plant

height

No. of

nodes

Internodes

length

No. of

monopodial

branches

No. of

sympodial

branches

Node for

first effective

sympodial branch

Nodes above

white flower

Nodes above

cracked boll

Replications 2 46.27 1.542 0.0025 0.0035 3.847 0.3348 0.0008 0.0502

Boron (B) 2 705.55** 9.056** 0.2309** 0.0868** 9.542** 0.5117* 2.9653** 1.5050**

Mepiquat chloride (M) 2 1582.37** 21.292** 0.5036** 0.2917** 18.042** 0.5318* 4.3661** 2.8782**

Planting density (P) 1 1948.44** 72.338** 5.8542** 0.2269** 68.907** 0.5582* 2.5917** 1.4146**

B×M 4 6.53ns 0.222ns 0.0051ns 0.0035 0.250ns 0.0121ns 0.1945** 0.1519**

B×P 2 22.52ns 0.130ns 0.0113ns 0.0012ns 0.005ns 0.0054ns 0.1009ns 0.0214ns

M×P 2 53.87ns 0.060ns 0.0542ns 0.0046ns 0.032ns 0.0012ns 0.0121ns 0.0272ns

B×M×P 4 1.15ns 0.019ns 0.0010ns 0.0081ns 0.046ns 0.0066ns 0.0494ns 0.0497ns

Error 34 40.71 1.556 0.0201 0.0194 1.583 0.1212 0.0469 0.0341

Total 53


Mean sum of squares

Plant

height

No. of

nodes

Internodes

length

No. of

monopodial

branches

No. of

sympodial

branches

Node for

first effective

sympodial branch

Nodes above

white flower

Nodes above

cracked boll

Replications 2 58.59 5.366 0.024 0.005 2.352 0.079 0.025 0.012

Boron (B) 2 1299.56** 12.574** 0.410** 0.154* 12.558** 3.236** 3.970** 1.641**

Mepiquat chloride (M) 2 1761.78** 23.949** 0.413** 0.699** 20.701** 17.073** 2.757** 3.359**

Planting density (P) 1 1942.92** 81.894** 6.331** 0.296** 84.425** 3.724** 2.140** 3.149**

B×M 4 11.53ns 0.095ns 0.004ns 0.013ns 0.036ns 0.377ns 0.174* 0.071*

B×P 2 18.56ns 0.019ns 0.009ns 0.001ns 0.096ns 0.311ns 0.100ns 0.028ns



Error 34 36.16 1.052 0.022 0.039 0.985 0.285 0.061 0.025

Total 53

55

Table 4.3a: Influence of foliar applied mepiquat chloride and boron at various

planting densities on plant height (cm) of cotton (2014)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat

chloride, B: Boron; HSD for MC = 5.2125, HSD for B = 5.2125.

Table 4.3b: Influence of foliar applied mepiquat chloride and boron at various


Values sharing the same case letters do not differ significantly at p ≤ 0.05; P: Planting

density, B: Boron; HSD for P = 3.5245, HSD for B = 5.2125.









Treatments Control MC application

at squaring

MC application

at flowering

Mean (B)

Control 123.66 106.44 113.46 114.52 B

600 ppm B 131.94 112.94 122.55 122.48 A

1200 ppm B 136.55 116.52 127.54 126.87 A

Mean (MC) 130.72 A 111.97 C 121.18 B

Treatments Plant spacing Mean (B)

25 cm 15 cm

Control 109.56 119.49 114.52 B

600 ppm B 116.61 128.34 122.48 A

1200 ppm B 119.68 134.06 126.87 A

Mean (P) 115.28 B 127.30 A


at squaring

MC application

at flowering

Mean (B)

Control 137.40 120.38 129.72 129.17 C

600 ppm B 148.61 127.81 137.09 137.83 B

1200 ppm B 157.35 135.83 145.30 146.16 A

Mean (MC) 147.78 A 128.01 C 137.37 B


25 cm 15 cm

Control 123.99 134.34 129.17 C

600 ppm B 132.15 143.52 137.83 B

1200 ppm B 139.03 153.29 146.16 A

Mean (P) 131.72 B 143.72 A

56


planting densities on number of main stem nodes of cotton (2014)






25 cm 15 cm

Control 32.06 29.56 30.81 B

600 ppm B 32.89 30.61 31.75 AB

1200 ppm B 33.28 31.11 32.19 A

Mean (P) 32.74 A 30.43 B










25 cm 15 cm

Control 33.00 30.50 31.75 B

600 ppm B 33.94 31.44 32.69 A

1200 ppm B 34.61 32.22 33.42 A

Mean (P) 33.85 A 31.39 B




at squaring

MC application

at flowering

Mean (B)

Control 32.17 29.75 30.50 30.81 B

600 ppm B 32.83 30.75 31.67 31.75 AB

1200 ppm B 33.17 31.17 32.25 32.19 A

Mean (MC) 32.72 A 30.56 B 31.47 B


at squaring

MC application

at flowering

Mean (B)

Control 32.75 30.58 31.92 31.75 B

600 ppm B 33.83 31.50 32.75 32.69 A

1200 ppm B 34.67 32.25 33.33 33.42 A

Mean (MC) 33.75 A 31.44 C 32.67 B

57


planting densities on internodes length (cm) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 3.86 3.59 3.73 3.73 B

600 ppm B 4.03 3.68 3.88 3.87 A

1200 ppm B 4.13 3.75 3.97 3.95 A

Mean (MC) 4.01 A 3.67 C 3.86 B


25 cm 15 cm

Control 3.42 4.03 3.73 B

600 ppm B 3.55 4.19 3.87 A

1200 ppm B 3.59 4.31 3.95 A

Mean (P) 3.52 B 4.18 A


at squaring

MC application

at flowering

Mean (B)

Control 4.21 3.95 4.08 4.08 C

600 ppm B 4.40 4.07 4.20 4.22 B

1200 ppm B 4.55 4.23 4.38 4.38 A

Mean (MC) 4.39 A 4.08 C 4.22 B


25 cm 15 cm

Control 3.76 4.41 4.08 C

600 ppm B 3.89 4.56 4.22 B

1200 ppm B 4.02 4.75 4.38 A

Mean (P) 3.89 B 4.57 A

58


planting densities on number of monopodial branches of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 1.88 1.67 1.83 1.79 B

600 ppm B 2.00 1.71 1.88 1.86 AB

1200 ppm B 2.04 1.79 1.96 1.93 A

Mean (MC) 1.97 A 1.72 B 1.89 A


25 cm 15 cm

Control 1.86 1.72 1.79 B

600 ppm B 1.92 1.81 1.86 AB

1200 ppm B 2.00 1.86 1.93 A

Mean (P) 1.93 A 1.80 B


at squaring

MC application

at flowering

Mean (B)

Control 2.67 2.29 2.63 2.53 B

600 ppm B 2.83 2.46 2.67 2.65 AB

1200 ppm B 2.92 2.50 2.71 2.71 A

Mean (MC) 2.81 A 2.42 B 2.67 A


25 cm 15 cm

Control 2.61 2.44 2.53 B

600 ppm B 2.72 2.58 2.65 AB

1200 ppm B 2.78 2.64 2.71 A

Mean (P) 2.70 A 2.56 B

59


planting densities on number of sympodial branches of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 24.08 21.75 22.58 22.81 B

600 ppm B 24.75 22.92 23.75 23.81 AB

1200 ppm B 25.08 23.25 24.33 24.22 A

Mean (MC) 24.64 A 22.64 B 23.56 B


25 cm 15 cm

Control 23.94 21.67 22.81 B

600 ppm B 24.94 22.67 23.81 AB

1200 ppm B 25.33 23.11 24.22 A

Mean (P) 24.74 A 22.48 B


at squaring

MC application

at flowering

Mean (B)

Control 24.75 22.58 23.83 23.72 B

600 ppm B 25.58 23.58 24.75 24.64 A

1200 ppm B 26.50 24.25 25.42 25.39 A

Mean (MC) 25.61 A 23.47 C 24.67 B


25 cm 15 cm

Control 25.00 22.44 23.72 B

600 ppm B 25.94 23.33 24.64 A

1200 ppm B 26.56 24.22 25.39 A

Mean (P) 25.83 A 23.33 B

60


planting densities on node for first effective boll bearing (sympodial) branch of cotton

(2014)





(2014)





(2015)





(2015)




at squaring

MC application

at flowering

Mean (B)

Control 7.33 6.91 7.15 7.13 A

600 ppm B 6.96 6.70 6.87 6.84 AB

1200 ppm B 7.00 6.65 6.84 6.83 B

Mean (MC) 7.10 A 6.75 B 6.95 AB


25 cm 15 cm

Control 7.24 7.02 7.13 A

600 ppm B 6.93 6.76 6.84 AB

1200 ppm B 6.94 6.71 6.83 B

Mean (P) 7.04 A 6.83 B


at squaring

MC application

at flowering

Mean (B)

Control 10.39 8.00 9.20 9.20 A

600 ppm B 9.35 7.58 8.94 8.62 B

1200 ppm B 9.20 7.53 8.37 8.37 B

Mean (MC) 9.65 A 7.71 C 8.83 B


25 cm 15 cm

Control 9.61 8.78 9.20 A

600 ppm B 8.79 8.45 8.62 B

1200 ppm B 8.57 8.16 8.37 B

Mean (P) 8.99 A 8.47 B

61


planting densities on nodes above white flower (NAWF) of cotton (2014)


chloride, B: Boron; HSD for MC = 0.1770, HSD for B = 0.1770, HSD for MC×B interaction = 0.4139.








chloride, B: Boron; HSD for MC = 0.2023, HSD for B = 0.2023, HSD for MC×B interaction

= 0.4729.






at squaring

MC application

at flowering

Mean (B)

Control 5.66 a 4.94 b 5.25 ab 5.28 A

600 ppm B 5.25 ab 4.34 c 5.01 b 4.87 B

1200 ppm B 5.16 b 3.83 d 4.43 c 4.47 C

Mean (MC) 5.36 A 4.37 C 4.89 B


25 cm 15 cm

Control 5.51 5.05 5.28 A

600 ppm B 5.01 4.73 4.87 B

1200 ppm B 4.76 4.18 4.47 C

Mean (P) 5.09 A 4.65 B


at squaring

MC application

at flowering

Mean (B)

Control 7.09 a 6.40 bcd 6.74 ab 6.74 A

600 ppm B 6.44 bc 5.93 de 6.27 cd 6.21 B

1200 ppm B 6.41 bc 5.26 f 5.75 e 5.80 C

Mean (MC) 6.65 A 5.86 C 6.25 B


25 cm 15 cm

Control 6.86 6.62 6.74 A

600 ppm B 6.43 6.00 6.21 B

1200 ppm B 6.07 5.54 5.80 C

Mean (P) 6.45 A 6.05 B

62


planting densities on nodes above cracked boll (NACB) of cotton (2014)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: mepiquat

chloride, P: Planting density, B: Boron; HSD for MC = 0.1510, HSD for B = 0.1510, HSD

for B×MC interaction = 0.3530.




chloride, P: Planting density, B: Boron; HSD for P = 0.1021, HSD for B = 0.1510.




chloride, P: Planting density, B: Boron; HSD for MC = 0.1293, HSD for B = 0.1293, HSD

for MC×B interaction = 0.3023.






at squaring

MC application

at flowering

Mean (B)

Control 4.57 a 4.01 bc 4.22 b 4.27 A

600 ppm B 4.23 ab 3.52 d 4.01 bc 3.92 B

1200 ppm B 4.24 ab 3.12 e 3.72 cd 3.69 C

Mean (MC) 4.35 A 3.55 C 3.98 B


25 cm 15 cm

Control 4.45 4.09 4.27 A

600 ppm B 4.04 3.80 3.92 B

1200 ppm B 3.88 3.51 3.69 C

Mean (P) 4.12 A 3.80 B


at squaring

MC application

at flowering

Mean (B)

Control 5.97 a 5.12 cd 5.35 bc 5.48 A

600 ppm B 5.44 b 4.66 ef 5.19 bc 5.09 B

1200 ppm B 5.37 bc 4.42 f 4.86 de 4.88 C

Mean (MC) 5.59 A 4.73 C 5.13 B


25 cm 15 cm

Control 5.76 5.19 5.48 A

600 ppm B 5.30 4.89 5.09 B

1200 ppm B 5.12 4.65 4.88 C

Mean (P) 5.39 A 4.91 B

63

and mepiquat chloride interactively decreased the NACB, as compared to control, at both

planting densities during both years. Maximum decrease in NACB (26-32%) were caused

by 1200 ppm B solution in combination with mepiquat chloride spray at squaring stage

(Tables 4.17a, 4.18a). Similarly, increasing the planting density resulted in a decrease in

NACB (8-9%), during both years (Tables 4.17b, 4.18b).

4.1.2. Discussion

Plant architecture is the three dimensional arrangement (shape, size and orientation)

of above ground canopy or plant parts that influences the agronomic and physiological

performance of crops by altering the tendency of plants for light interception and use

efficiency, and ultimately photosynthesis (Reihardt and Kuhlemerier, 2002). Plant growth

and architecture also influences the ability of plants to resist the outgrowth of insect pests

and diseases, compete for various resources, requirements of soil fertility and plant

population density, as well as the yield potential of crops (Maddonni et al., 2001; Stewart,

2005). In present study, foliar applied B, mepiquat chloride, and planting density modulated

the plant growth and development of cotton. It was observed that plant height and

internodes length was increased by foliar applied B and higher planting density while

decreased by mepiquat chloride. On the other hand, the number of nodes, sympodial

branches and monopodial branches were increased by B while decreased by mepiquat

chloride application and higher planting density.

The increase in plant growth attributes by foliar B treatment might be due to the

increased cell elongation and cell division typically in the meristematic regions (Miwa and

Fujiwara, 2010b). Boron is involved in synthesis and functioning of cell wall through

dimerization of pectic polysaccharide, rhammnogalacturonan II (RG II), by borate cross

linking which is essential for cell elongation (O’Neill et al., 2004; Miwa and Fujiwara,

2010a). Boron is structural component of cytoskeleton thus regulates the cell division

(Bassil et al., 2004). Similarly, Dordas (2006a) and Gormus (2006) has also reported

similar increase in plant height, number of main stem nodes and internodes length of cotton

in response to foliar applied boron. Increase in plant height and decease in main stem nodes

at higher planting density was probably due to interplant competition for light interception.

Whereas, the decrease in main stem nodes was the cause of increased internodes length and

lesser number of monopodial and sympodial branches. Similar, results have been reported

previously by Obasi and Msaakpa (2005), Ali et al. (2009a) and Kaggwa-Asiimwe et al.

(2013) indicating an increase in plant height and internodes length, with a decrease in

number of main stem nodes, and monopodial and sympodial branches at high planting

64

density. On the other hand, mepiquat chloride application reduced the plant growth

attributes at all levels of B and planting densities. The reduction in internodes elongation

and plant height by mepiquat chloride application is attributed to decreased gibberellic acid

concentration in cells (Wang et al., 2014). In present study, the growth reduction was more

pronounced by mepiquat chloride application at squaring. It might be due to the fact that

plants had already gained more growth till mepiquat chloride application at flowering, as

compared to squaring stage. Similar, reduction in cotton growth was reported by Abbas et

al. (2010), Gwathmey and Clement (2010) and Mao et al. (2014).

4.1.3. Phenological development

4.1.3.1. Calendar time

The days for initiation of squaring did not differ significantly in response to foliar

applied B and mepiquat chloride as well as planting density. Interaction between mepiquat

chloride and B, mepiquat chloride and planting density, B and planting density as well as

three way interaction among mepiquat chloride, B and planting was also non-significant

for days to squaring initiation (Tables 4.19, 4.20). However, mepiquat chloride, B and

planting density significantly varied for days to flowering initiation, days to boll opening

initiation, mean maturity days, earliness index and production rate index. Moreover, the

interaction between mepiquat chloride and B as well as B and planting density was

significant, while, the interaction between mepiquat chloride and planting density, and

three way interaction among mepiquat chloride, B and planting density was non-significant

for production rate index. However, the interactive effect of mepiquat chloride and B, boron

and planting density, mepiquat chloride and planting density, as well as three way

interaction of mepiquat chloride, B and planting density was non-significant for days to

flowering initiation, days to boll opening initiation, mean maturity days and earliness index

(Tables 4.19, 4.20). The boll maturation period was significantly varied for planting

densities but the effect of B, mepiquat chloride and the interactions between B and

mepiquat chloride, B and mepiquat chloride, mepiquat chloride and planting density, and

interaction between B, mepiquat chloride and planting density was non-significant (Tables

4.19, 4.20).

Flowering was commenced earlier (≈2.4 and 2 days during 2014 and 2015,

respectively) by foliar application of B with minimum days for flowering occurring by

foliar application of 1200 ppm B solution, as compared to control; however, the effect of

600 ppm B solution was statistically similar, during both years (Tables 4.23a, 4.24a).

Mepiquat chloride produced similar effect on days to flowering initiation with 3 days earlier

65

flowering occurring by application of mepiquat chloride at squaring stage, as compared to

control during both years (Tables 4.23a, 4.24a). Similarly, earlier flowering (1.5 and 2.2

days during 2014 and 2015, respectively) was occurred at higher planting density, as

compared to lower planting density, during both years (Tables 4.23b, 4.2b). Similar to

flowering, boll opening took less time (2.8 and 2.3 days during 2014 and 2015,

respectively) by application 1200 ppm B solution as compared to control and it was

followed by application of 600 ppm B solution (Tables 4.25a, 4.26a). Mepiquat chloride

application decreased the days to boll opening initiation and the application of mepiquat

chloride at squaring stage was most effective in earlier commencement of boll opening (3.4

and 3 days during 2014 and 2015, respectively) than control (Tables 4.25a, 4.26a). Boll

opening also commenced earlier by sowing the crop at higher planting density by

approximately 3 days as compared to lower planting density, during both years (Tables

4.25b, 4.26b). The boll maturation period was significantly less at higher planting density

as compared to lower planting density, during both years (Tables 27, 28).

Foliar application of B and mepiquat chloride decreased the mean maturity days, as

compared to control, during both years. It was observed that application of 1200 ppm B

caused maximum decrease in mean maturity days (1.5 and 2.1 days during 2014 and 2015,

respectively) and it was followed by application of 600 ppm B solution (Tables 4.29a,

4.30a). Whereas, application of mepiquat chloride at squaring stage decreased the mean

maturity days (2 and 2.1 days during 2014 and 2015, respectively) to a maximum level

(Tables 4.29a, 4.30a). Similarly, lower mean maturity days (≈1.3 and 1 days during 2014

and 2015, respectively) were exhibited by higher planting density, during both years

(Tables 4.29b, 4.30b). The earliness index was improved by foliar application of B (5-8%)

and highest earliness index was recorded by application of 1200 ppm B solution but the

effect 600 ppm B was similar (Tables 4.31a, 4.32a). The earliness index was also increased

(7-8%) by the effect of mepiquat chloride and application of mepiquat chloride at squaring

stage produced highest earliness index, during both years (Tables 4.31a, 4.32a). In case of

planting density, significantly higher earliness index (3-4%) was observed by sowing the

crop at higher planting density, during both years (Tables 4.31b, 4.32b).

The production rate index was substantially improved by application of mepiquat

chloride and B at different planting densities, as compared to control. It was noticed that

application of 1200 ppm B in combination with mepiquat chloride at squaring stage caused

maximum increase in production rate index (34-39%), as compared to control during both

years; however, the effect of 1200 ppm B in combination with mepiquat chloride

66

Table 4.19: Analysis of variance for influence of foliar applied mepiquat chloride and boron at various planting densities on phenology

of cotton (2014)


Table 4.20: Analysis of variance for influence of foliar applied mepiquat chloride and boron at various planting densities on phenology

of cotton (2015)



Mean sum of squares

Days to squaring

initiation

Days to flowering

initiation

Days to boll opening

initiation

Boll maturation

period

Mean maturity days

Earliness index

Production rate index

Replications 2 2.162 5.574 5.597 1.144 5.159 32.186 0.689

Boron (B) 2 0.009ns 25.699** 34.889* 0.921ns 12.511* 78.165* 49.174**

Mepiquat chloride (M) 2 0.024ns 55.005** 63.597** 0.519ns 18.478** 115.513** 46.722**

Planting density (P) 1 5.607ns 30.375** 115.574** 27.449** 21.863** 136.740** 99.933**

B×M 4 0.059ns 0.116ns 0.111ns 0.102ns 0.421ns 2.619ns 3.911**

B×P 2 0.009ns 0.264ns 0.352ns 0.088ns 0.139ns 0.861ns 3.443*

M×P 2 0.101ns 0.681ns 0.421ns 0.130ns 0.248ns 1.574ns 0.315ns

B×M×P 4 0.075ns 0.069ns 0.241ns 0.144ns 0.077ns 0.486ns 0.194ns

Error 34 1.396 2.545 6.641 2.663 2.708 16.915 0.723

Total 53


Mean sum of squares

Days to

squaring

initiation

Days to

flowering

initiation

Days to boll

opening

initiation

Boll

maturation

period

Mean

maturity days

Earliness

index

Production

rate index

Replications 2 1.970 0.542 0.421 1.685 0.7231 4.522 2.3091

Boron (B) 2 0.125ns 16.542** 23.977** 0.699ns 21.8809** 136.691** 36.3743**

Mepiquat chloride (M) 2 0.042ns 48.167** 51.810** 0.338ns 20.7573** 129.728** 33.1549**

Planting density (P) 1 5.671ns 67.782** 132.227** 10.667* 10.8541* 67.827* 35.9660**

B×M 4 0.021ns 0.208ns 0.171ns 0.018ns 1.1534ns 7.214ns 2.2176*

B×P 2 0.032ns 1.727ns 2.116ns 0.042ns 0.0824ns 0.514ns 2.4730*

M×P 2 0.032ns 0.241ns 0.366ns 0.014ns 0.1326ns 0.830ns 0.1999ns

B×M×P 4 0.081ns 0.852ns 0.921ns 0.014ns 0.1874ns 1.168ns 0.0748ns

Error 34 1.424 2.375 3.289 1.999 1.5515 9.697 0.5977

Total 53

67

Table 4.21: Influence of foliar applied mepiquat chloride and boron on days to

squaring initiation (days) of cotton at various planting densities (2014)

MC: mepiquat chloride, P: Planting density, B: Boron.

Table 4.22: Influence of foliar applied mepiquat chloride and boron at various

planting densities on days to squaring initiation (days) of cotton (2015)



planting densities on days to flowering initiation (days) of cotton (2014)







Treatments Plant spacing

25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 34.87 34.73 34.83 34.18 34.40 34.02 34.51

600 ppm B 34.63 34.77 35.03 34.27 34.00 34.10 34.47

1200 ppm B 34.77 34.73 34.93 34.00 34.27 34.23 34.49

Mean (MC×P) 34.76 34.74 34.93 34.15 34.22 34.12

Mean (P) 34.81 34.16


25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 36.83 37.00 36.83 36.17 36.00 36.33 36.53

600 ppm B 36.83 36.67 36.67 36.17 36.00 36.33 36.44

1200 ppm B 37.00 36.83 37.00 36.33 36.33 36.17 36.61

Mean (MC×P) 36.89 36.83 36.83 36.22 36.11 36.28

Mean (P) 36.85 36.20


at squaring

MC application

at flowering

Mean (B)

Control 57.75 54.50 57.58 56.61 A

600 ppm B 56.00 53.25 56.08 55.11 B

1200 ppm B 55.25 52.17 55.33 54.25 B

Mean (MC) 56.33 A 53.31 B 56.33 A


25 cm 15 cm

Control 57.50 55.72 56.61 A

600 ppm B 55.78 54.44 55.11 B

1200 ppm B 54.94 53.56 54.25 B

Mean (P) 56.07 A 54.57 B

68






planting densities on days to flower initiation (days) of cotton (2015)




planting densities on days to boll opening initiation (days) of cotton (2014)








at squaring

MC application

at flowering

Mean (B)

Control 59.58 56.83 59.42 58.61 A

600 ppm B 58.50 55.83 58.50 57.61 AB

1200 ppm B 57.67 54.58 57.83 56.69 B

Mean (MC) 58.58 A 55.75 B 58.58 A


25 cm 15 cm

Control 59.61 57.61 58.61 A

600 ppm B 58.50 56.72 57.61 AB

1200 ppm B 58.17 55.22 56.69 B

Mean (P) 58.76 A 56.52 B


at squaring

MC application

at flowering

Mean (B)

Control 99.67 96.25 99.42 98.44 A

600 ppm B 97.92 94.83 97.92 96.89 AB

1200 ppm B 97.00 93.42 96.58 95.67 B

Mean (MC) 98.19 A 94.83 B 97.97 A


25 cm 15 cm

Control 100.06 96.83 98.44 A

600 ppm B 98.33 95.44 96.89 AB

1200 ppm B 97.00 94.33 95.67 B

Mean (P) 98.46 A 95.54 B

69










planting densities on boll maturation period (days) of cotton (2014)


density, B: Boron; HSD for P = 0.9015.


planting densities on boll maturation period (days) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 103.08 100.08 102.75 101.97 A

600 ppm B 101.75 98.92 101.50 100.72 AB

1200 ppm B 100.83 97.50 100.67 99.67 B

Mean (MC) 101.89 A 98.83 B 101.64 A


25 cm 15 cm

Control 103.44 100.50 101.97 A

600 ppm B 102.00 99.44 100.72 AB

1200 ppm B 101.61 97.72 99.67 B

Mean (P) 102.35 A 99.22 B


25 cm 15 cm

Control 42.56 41.11 41.83

600 ppm B 42.56 41.00 41.78

1200 ppm B 42.06 40.78 41.42

Mean (P) 42.39 A 40.96 B


25 cm 15 cm

Control 43.83 42.89 43.36

600 ppm B 43.50 42.72 43.11

1200 ppm B 43.44 42.50 42.97

Mean (P) 43.59 A 42.70 B

70


planting densities on mean maturity days of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 142.04 140.53 141.28 141.28 A

600 ppm B 140.83 138.68 140.24 139.92 B

1200 ppm B 140.91 138.54 139.87 139.77 B

Mean (MC) 141.26 A 139.25 B 140.46 AB


25 cm 15 cm

Control 141.83 140.74 141.28 A

600 ppm B 140.56 139.27 139.92 B

1200 ppm B 140.50 139.05 139.77 B

Mean (P) 140.96 A 139.69 B


at squaring

MC application

at flowering

Mean (B)

Control 143.72 142.53 143.17 143.14 A

600 ppm B 142.70 140.36 141.79 141.62 B

1200 ppm B 142.33 139.45 141.23 141.00 B

Mean (MC) 142.92 A 140.78 B 142.06 A


25 cm 15 cm

Control 143.58 142.71 143.14 A

600 ppm B 142.01 141.23 141.62 B

1200 ppm B 141.52 140.48 141.00 B

Mean (P) 142.37 A 141.47 B

71


planting densities on earliness index (%) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 69.89 73.68 71.79 71.79 B

600 ppm B 72.92 78.30 74.40 75.21 A

1200 ppm B 72.72 78.65 75.33 75.56 A

Mean (MC) 71.84 B 76.88 A 73.84 AB


25 cm 15 cm

Control 70.42 73.16 71.79 B

600 ppm B 73.60 76.81 75.21 A

1200 ppm B 73.76 77.37 75.56 A

Mean (P) 72.60 B 75.78 A


at squaring

MC application

at flowering

Mean (B)

Control 65.69 68.67 67.07 67.14 B

600 ppm B 68.26 74.10 70.52 70.96 A

1200 ppm B 69.18 76.37 71.93 72.49 A

Mean (MC) 67.71 B 73.04 A 69.84 B


25 cm 15 cm

Control 66.06 68.23 67.14 B

600 ppm B 69.99 71.93 70.96 A

1200 ppm B 71.19 73.80 72.49 A

Mean (P) 69.08 B 71.32 A

72


planting densities on production rate index (kg ha-1 day-1) of cotton (2014)


chloride, B: Boron; HSD for MC = 0.6948, HSD for B = 0.6948, HSD for MC×B

interaction = 1.6245.




density, B: Boron; HSD for P = 0.4698, HSD for B = 0.6948, HSD for B×P interaction =

1.2099.









density, B: Boron; HSD for P = 0.4271, HSD for B = 0.6316, HSD for P×B interaction =

1.1000.


at squaring

MC application

at flowering

Mean (B)

Control 17.14 e 19.03 d 18.58 de 18.25 C

600 ppm B 18.76 de 21.57 bc 20.04 cd 20.12 B

1200 ppm B 18.89 d 23.81 a 21.95 b 21.55 A

Mean (MC) 18.27 C 21.47 A 20.19 B


25 cm 15 cm

Control 17.02 d 19.49 c 18.25 C

600 ppm B 19.13 c 21.12 b 20.12 B

1200 ppm B 19.70 c 23.39 a 21.55 A

Mean (P) 18.61 B 21.34 A


at squaring

MC application

at flowering

Mean (B)

Control 15.86 f 17.44 de 16.85 ef 16.72 C

600 ppm B 17.12 def 19.71 bc 18.45 cd 18.42 B

1200 ppm B 17.38 de 21.29 a 19.94 ab 19.54 A

Mean (MC) 16.78 C 19.48 A 18.41 B


25 cm 15 cm

Control 15.81 d 17.62 c 16.72 C

600 ppm B 18.01 bc 18.83 b 18.42 B

1200 ppm B 18.40 bc 20.67 a 19.54 A

Mean (P) 17.41B 19.04 A

73

application at flowering stage produced statistically similar results during 2014 (Tables

4.33a, 4.34a). The production rate index was increased by increasing the planting density

but application of B improved the production rate index at both planting densities (16 and

18% at lower and higher planting density, respectively), as compared to control. However,

the treatment with 1200 ppm B at higher planting density produced the highest production

rate index (Tables 4.33b, 4.34b).


The heat unit accumulation from sowing to squaring did not differ significantly by

the influence of B, mepiquat chloride, planting density as well as the interactions between

B and mepiquat chloride, B and planting density, mepiquat chloride and planting density,

and three way interaction among B, mepiquat chloride and planting density, during both

years (Tables 4.35, 4.36). The heat unit accumulation from sowing to flowering and sowing

to boll opening was significantly affected by B, mepiquat chloride and planting density

during both years. Moreover, the interaction between B and planting density was significant

for heat unit accumulation from sowing to flowering during 2015 but non-significant during

2014. The interactions between B and mepiquat chloride, mepiquat chloride and planting

density, and three way interaction of B, mepiquat chloride and planting density was non-

significant for heat unit accumulation from sowing to flowering and sowing to boll opening,

during both years; however, the interaction between B and planting density was also non-

significant for heat unit accumulation form sowing to boll opening, during both years

(Tables 4.35, 4.36).

The heat unit accumulation form squaring to flowering was significantly affected

by B and mepiquat chloride during both years; while, planting density and interaction

between B and planting density was also significant during 2015. However, the effect of

planting density, and interaction between B and planting density during 2014, and

interactions between B and mepiquat chloride, mepiquat chloride and planting density, and

three way interaction among B, mepiquat chloride and planting density was non-significant

for heat unit accumulation from squaring to flowering, during both years (Tables 4.35,

4.36). Heat unit accumulation form flowering to boll opening significantly differed by

planting density during 2014 but did not affect significantly during 2015. Furthermore, the

effect of B, mepiquat chloride and interactions between B and mepiquat chloride, B and

planting density, mepiquat chloride and planting density and three way interaction among

B, mepiquat chloride and planting density was non-significant for heat unit accumulation

form flowering to boll opening during both years (Tables 4.35-4.36).

74

The foliar application of B decreased the heat unit accumulation from sowing to

flowering (40 and 20 GDD during 2014 and 2015, respectively), as compared to control,

and application of 1200 ppm B was found most effective in this regard but 600 ppm B

produced similar results, during both years (Tables 4.39a, 4.40a). Similarly, mepiquat

chloride application at squaring stage caused the highest reduction in heat unit

accumulation from sowing to flowering (51 and 34 GDD during 2014 and 2015,

respectively), as compared to control (Tables 4.39a, 4.40a). Increase in planting density

behaved similarly with a decrease in heat unit accumulation from sowing to flowering (26

and 42 GDD during 2014 and 2015, respectively), as compared to lower planting density.

However, during 2015 boron application and higher planting density interactively

decreased the heat unit accumulation and application of 1200 ppm B at higher planting

density caused maximum decrease (Tables 4.39b, 4.40b). Less heat units were accumulated

from squaring to flowering in response to foliar applied boron with minimum heat units

accumulated by the effect of 1200 ppm B (342 and 331 GDD during 2014 and 2015,

respectively). However, the effect of 600 ppm B was statistically similar during both years

(Tables 4.41, 4.42a). Similarly, mepiquat chloride application decreased the heat units from

squaring to flowering, as compared to control during both years. It was observed that

application of mepiquat chloride at squaring stage caused minimum heat unit accumulation

from squaring to flowering (330 and 319 GDD during 2014 and 2015, respectively) (Tables

4.41, 4.42a). However, during 2014 the planting density did not affect the heat unit

accumulation from squaring to flowering but during 2015 significantly interacted with

foliar boron. Lowest heat units were accumulated by the influence of 1200 ppm B at higher

planting density (323 GDD) but the effect of application of 600 ppm B at higher planting

density was similar (Table 4.42b).

Heat unit accumulation form sowing to boll opening were significantly decreased

by application of B (39 and 37 GDD during 2014 and 2015, respectively), as compared to

control, and 1200 ppm B solution was superior among all with minimum heat units

accumulated (1684 and 1588 GDD during 2014 and 2015, respectively), although the effect

of 600 ppm B was statistically at par, during both years (Tables 4.43a, 4.44a). Mepiquat

chloride application also decreased the heat unit accumulation from sowing to boll opening

(49 GDD during both years), as compared to control. Foliar application of mepiquat

chloride at squaring stage resulted in minimum heat unit accumulation (1670 and 1575

GDD during 2014 and 2015, respectively) from sowing to boll opening (Tables 4.43a,

75

Table 4.35: Analysis of variance for influence of foliar applied mepiquat chloride and

boron at various planting densities on thermal time of cotton (2014)



boron at various planting densities on thermal time of cotton (2015)



Mean sum of squares

Sowing-squaring

Sowing-flowering

Squaring-flowering

Sowing-boll

opening

Flowering-boll opening

Replications 2 712.02 2054.0 353.0 927.7 360.72

Boron (B) 2 3.15ns 7350.1** 7285.3** 6821.2* 128.72ns

Mepiquat chloride (M) 2 4.99ns 14394.6** 14428.4** 13752.7** 14.39ns

Planting density (P) 1 1865.72ns 8960.9** 2648.9ns 22693.5** 3128.17*

B×M 4 21.46ns 241.0ns 320.2ns 47.2ns 307.28ns

B×P 2 4.82ns 293.7ns 370.1ns 10.7ns 208.39ns

M×P 2 33.21ns 9.2ns 58.4ns 282.9ns 334.06ns

B×M×P 4 23.74ns 300.4ns 452.7ns 59.1ns 236.44ns

Error 34 454.64 615.5 1074.8 1347.3 724.15

Total 53


Mean sum of squares

Sowing-

squaring

Sowing-

flowering

Squaring-

flowering

Sowing-

boll

opening

Flowering-

boll opening

Replications 2 389.17 317.1 436.8 99.0 754.89

Boron (B) 2 12.52ns 1992.3* 2319.1** 6284.5** 1426.17ns


Planting density (P) 1 1134.56ns 23668.1** 14438.4** 34302.2** 945.85ns

B×M 4 78.74ns 304.8ns 290.5ns 40.1ns 538.83ns

B×P 2 93.25ns 2105.2** 1774.3** 557.0ns 529.80ns

M×P 2 37.21ns 406.9ns 258.2ns 91.2ns 667.35ns

B×M×P 4 40.81ns 183.0ns 350.4ns 265.4ns 770.80ns

Error 34 442.82 579.7 299.0 840.3 568.14

Total 53

76

Table 4.37: Influence of foliar applied mepiquat chloride and boron on thermal time

(GDD) taken from sowing to squaring initiation of cotton at various planting densities

(2014)



(GDD) taken from sowing to squaring initiation of cotton at various planting densities

(2015)


Table 4.39a: Influence of foliar applied mepiquat chloride and boron on thermal time

(GDD) taken from sowing to flowering initiation of cotton at various planting densities

(2014)



Table 4.39b: Influence of foliar applied mepiquat chloride and boron on thermal time


(2014)




25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 659.12 656.52 657.88 646.79 650.79 643.64 652.46

600 ppm B 655.25 657.28 661.65 647.87 643.23 644.59 651.64

1200 ppm B 657.23 656.51 660.42 643.23 648.28 647.64 652.22

Mean (MC×P) 657.20 656.77 659.98 645.96 647.43 645.29

Mean (P) 657.98 646.23


25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 605.41 608.06 605.41 593.46 591.22 597.37 600.15

600 ppm B 606.58 601.92 601.92 610.42 591.22 596.96 601.50

1200 ppm B 608.07 605.84 608.07 596.96 596.94 594.22 601.68

Mean (MC×P) 606.68 605.27 605.13 600.28 593.13 596.18

Mean (P) 605.70 596.53


at squaring

MC application

at flowering

Mean (B)

Control 1055.25 996.24 1051.08 1034.19 A 600 ppm B 1032.78 991.18 1024.59 1016.18 A

1200 ppm B 1010.50 959.04 1012.02 993.85 B Mean (MC) 1032.84 A 982.15 B 1029.23 A


25 cm 15 cm

Control 1051.56 1016.82 1034.19 A

600 ppm B 1025.71 1006.65 1016.18 A

1200 ppm B 1005.60 982.11 993.85 B

Mean (P) 1027.62 A 1001.86 B

77



(2015)





(2015)


density, B: Boron; HSD for P = 13.301, HSD for B = 19.671, HSD for B×P = 34.255.


(GDD) taken from squaring to flowering initiation of cotton at various planting

densities (2014)





densities (2015)




at squaring

MC application

at flowering

Mean (B)

Control 967.62 925.05 965.44 952.70 A

600 ppm B 951.04 909.49 951.06 937.20 AB

1200 ppm B 938.10 919.00 940.81 932.63 B

Mean (MC) 952.25 A 917.85 B 952.44 A


25 cm 15 cm

Control 968.33 a 937.08 ab 952.70 A

600 ppm B 951.00 ab 923.39 bc 937.20 AB

1200 ppm B 966.01 a 899.26 c 932.63 B

Mean (P) 961.78 A 919.91 B


at squaring

MC application

at flowering

Mean (B)

Control 402.30 342.59 400.32 381.73 A

600 ppm B 381.22 340.93 371.47 364.54 AB

1200 ppm B 360.27 306.65 357.98 341.63 B

Mean (MC) 381.26 A 330.05 B 376.59 A


at squaring

MC application

at flowering

Mean (B)

Control 368.19 325.41 364.05 352.55 A

600 ppm B 342.54 312.92 351.62 335.69 B

1200 ppm B 335.59 317.61 339.66 330.95 B

Mean (MC) 348.77 A 318.65 B 351.78 A

78



densities (2015)


chloride, B: Boron; HSD for P = 9.5519, HSD for B = 14.127, HSD for B×P = 24.601.


(GDD) taken from sowing to boll opening initiation of cotton at various planting

densities (2014)





densities (2014)





densities (2015)




25 cm 15 cm

Control 362.04 a 343.06 ab 352.55 A

600 ppm B 347.53 ab 323.86 bc 335.69 B

1200 ppm B 358.69 a 303.22 c 330.95 B

Mean (P) 356.08 A 323.38 B


at squaring

MC application

at flowering

Mean (B)

Control 1738.90 1691.76 1736.33 1722.33 A 600 ppm B 1715.00 1670.00 1716.66 1700.55 AB

1200 ppm B 1703.88 1648.97 1697.74 1683.53 B Mean (MC) 1719.26 A 1670.25 B 1716.91 A


25 cm 15 cm

Control 1743.70 1700.96 1722.33 A

600 ppm B 1720.71 1680.39 1700.55 AB

1200 ppm B 1703.54 1663.52 1683.53 B

Mean (P) 1722.65 A 1681.63 B


at squaring

MC application

at flowering

Mean (B)

Control 1643.40 1595.30 1638.22 1625.64 A

600 ppm B 1622.61 1576.20 1618.16 1605.66 AB

1200 ppm B 1606.93 1553.46 1604.63 1588.34 B

Mean (MC) 1624.32 A 1574.99 B 1620.34 A

79



densities (2015)




(GDD) taken from flowering to boll opening initiation of cotton at various planting

densities (2014)



Table 4.46: Influence of foliar applied mepiquat chloride and boron on thermal time (GDD)

taken from flowering to boll opening initiation of cotton at various planting densities (2015)

P: Planting density, B: Boron.


25 cm 15 cm

Control 1649.16 1602.11 1625.64 A

600 ppm B 1626.24 1585.08 1605.66 AB

1200 ppm B 1619.70 1556.98 1588.34 B

Mean (P) 1631.70 A 1581.39 B


25 cm 15 cm

Control 692.15 684.14 688.14

600 ppm B 695.00 673.75 684.37

1200 ppm B 697.95 681.41 689.68

Mean (P) 695.03 A 679.77 B


25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 683.84 678.15 680.51 667.72 662.34 665.04 672.93

600 ppm B 678.78 674.43 672.50 664.36 658.98 661.71 668.46

1200 ppm B 677.98 610.39 672.70 659.69 658.54 654.94 655.71

Mean (MC×P) 680.20 654.32 675.23 663.92 659.95 660.56

Mean (P) 669.92 661.48

80

4.44a). Likewise, heat unit accumulation from sowing to boll opening was decreased (41

and 50 GDD during 2014 and 2015, respectively) by increasing the planting density. Least

heat unit accumulation (1682 and 1581 GDD during 2014 and 2015, respectively) from

sowing to boll opening took place when the crop was sown at higher planting density, as

compared to lower planting density, during both years (Tables 4.43b, 4.44b). Heat unit

accumulation from flowering to boll opening was influenced by planting density only

during 2014. It was observed that at higher planting density less heat units were

accumulated (15 GDD), as compared to lower planting density (Table 4.45).

4.1.4. Discussion

Phenological alterations were induced by foliage applied B, mepiquat chloride and

planting density. These alterations were assessed through plant architectural modification

(NAWF and NACB), calendar days as well as thermal time.

The results revealed that application of B and mepiquat chloride, and varying the

planting density significantly induced structural modifications that were indicative of

earlier maturity. It was observed that foliar applied B and mepiquat chloride significantly

interacted in decreasing the NAWF and NACB. This might be due to enhanced reserve

remobilization by B (Saleem et al., 2016b) and mepiquat chloride (Gwathmey and Clement,

2010) which caused earlier physiological cutout as indicated by a decrease in NAWF.

Moreover, higher boll retention and boll load on cotton plants causes a shift of balance from

vegetative to reproductive growth thus leading to earlier physiological cutout (Gwathmey

and Craig, 2003). However, in case of B no previous studies are available regarding earlier

physiological cutout for comparison. However, Johnson et al. (2006) and Dodds et al.

(2010) reported a decrease in NAWF and NACB, respectively, by the influence of mepiquat

chloride. Increasing the planting density also caused earlier physiological cutout although

it did not interact with B and mepiquat chloride. Earlier physiological cutout at higher

planting density might be due to higher inter-plant competition that did not allow the plants

to get highly vegetative. Moreover, high planting density enhances the retention of first

position bolls and earlier boll retention leading to earliness in maturity (Wilson et al., 2007).

The calendar and thermal time required for squaring was non-significant for all the

treatments; however, days to flowering, boll opening and mean maturity days were

significantly decreased by foliar application of B, mepiquat chloride as well as higher

planting density. The earlier initiation of flowering by B might be associated with its role

in flower production as its deficiency causes abortion of the apical meristems resulting in

lack of flower development (Loomis and Durst, 1991). Mepiquat chloride application

81

decreases the vegetative growth and exalts assimilate and nutrient partitioning to the

reproductive structures thus boosting the production of flowers and bolls (Kerby et al.,

1996). On the other hand, increasing the planting density decreases the production of

monopodial and late season flowers and bolls that assists in the achievement of earlier

maturity with a concomitant decrease in days to flowering and boll opening (Jones and

Wells, 1998; Siebert et al., 2006). The results of present study further revealed that the

earlier maturity by the influence of either foliar applied B, mepiquat chloride or planting

density was associated with earlier flowering rather than reduction in boll maturation

period.

Moreover, B and mepiquat chloride treated plants especially at higher planting

density accumulated less heat units for the commencement of different growth stages i.e.

flowering and boll opening etc. This might be due to earlier shift in vegetative to

reproductive growth by the influence of B, mepiquat chloride and increasing planting

density. This also indicates that foliar applied B and mepiquat chloride as well as increasing

the planting density decreases the thermal time requirement to initiate different growth

stages.

The earliness index was significantly increased by foliar application of B and

mepiquat chloride, and increasing the planting density as well. The increase in earliness

index was associated with earlier boll opening by B, mepiquat chloride and planting density

treatments. Similar results were reported by Eleyan et al. (2014), that foliar application of

B improved the earliness index (upto 4%) in cotton. Likewise, Gwathmey and Craig (2003)

observed an increase in earliness index (percent of first pick) by application of mepiquat

chloride. Saleem et al. (2009) found an increase in earliness index by decreasing the row

spacing or increasing the plant density.

Production rate index is an important index of measuring earliness in relation to

yield and is associated with mean maturity days. Foliar application of B and mepiquat

chloride significantly interacted in improving the production rate index. It was observed

that both B and mepiquat chloride decreased the mean maturity days but did not influence

the boll maturation period. This indicates that the earliness in maturity was not achieved at

the expense of yield which might be the reason of enhanced production rate index by the

effect of B and mepiquat chloride. Similarly, B application significantly interacted with

planting density in improving the production rate index. Increasing the planting density

decreased the mean maturity days but it also decreased the boll maturation period.

Although, the bolls per plant and average boll weight was decreased at higher planting

82

density as compared to lower planting density but boll density was increased. Moreover, B

application further increased the boll density and also ameliorated boll weight at higher

planting density which ultimately resulted in enhanced production rate index. However,

Saleem et al. (2009) reported that production rate index was decreased by increasing the

planting density, although seed cotton yield was increased and mean maturity days were

decreased.

4.1.5. Allometric attributes

4.1.5.1. Dry matter accumulation

4.1.5.1.1. Vegetative dry matter

The pattern of vegetative dry matter accumulation exhibited an increase with

advancement of temporal crop growth (upto 120 DAS) and then declined with further

increase in time (135 DAS), during both years (Figures 4.1, 4.2). Foliar application of B

enhanced the vegetative dry matter as compared to control, during both years. An

increasing trend in production of vegetative dry matter was noticed by the influence of

boron upto 105 DAS and then started declining with further increase in duration, during

both years. Accumulation of vegetative dry matter was highest from 90-105 DAS either

with or without mepiquat chloride application at both planting densities, during 2014.

However, during 2015 maximum vegetative dry matter was accumulated from 75-90 DAS

under control and mepiquat chloride application at flowering stage, while, under mepiquat

chloride application at squaring maximum vegetative dry matter accumulation occurred

from 90-105 DAS, at both planting densities (Figures 4.1, 4.2).

Varying the planting density caused a differential accumulation of vegetative dry

matter until maturity. Increasing the planting density resulted in an increase in vegetative

dry matter accumulation from initial growth stages until maturity (45-135 DAS). Moreover,

the effect of B in increasing and mepiquat chloride in decreasing the vegetative dry matter

was more pronounced at lower and higher planting densities, respectively. Furthermore,

highest vegetative dry matter was recorded at 120 DAS, during both years (Figures 4.1,

4.2).

The effect of foliar applied B, mepiquat chloride and planting density was

significant on maximum vegetative dry matter accumulation (120 DAS). However, the

interactive effect of B and mepiquat chloride, B and planting density, mepiquat chloride

and planting density and three way interaction among B, mepiquat chloride and planting

density was non-significant on maximum vegetative dry matter, during both years (Tables

4.47, 4.48). Foliar applied B enhanced the accumulation of vegetative dry matter (10-14%),

83


boron at various planting densities on allometric attributes of cotton (2014)

DF: Degree of freedom; ns: Non-significant; *: Significant at p 0.05; significant at p 0.01



DF: Degree of freedom; ns: Non-significant; **: significant at p 0.01


Mean sum of squares

Vegetative

dry matter

Reproductive

dry matter

Total

dry

matter

Reproductive-

vegetative dry

matter ratio

Replications 2 1988 349 1832 0.003 Boron (B) 2 8135** 44067** 76288** 0.085** Mepiquat chloride (M) 2 18199** 16562** 513ns 0.582** Planting density (P) 1 95774** 213391** 538937** 0.040** B×M 4 173ns 524ns 705ns 0.004ns B×P 2 94ns 2220* 3184ns 0.006ns M×P 2 648ns 194ns 221ns 0.004ns B×M×P 4 22ns 146ns 157ns 0.001ns

Error 34 474 580 1326 0.008 Total 53


Mean sum of squares

Vegetative

dry matter

Reproductive

dry matter

Total dry

matter

Reproductive

-vegetative

dry matter

ratio

Replications 2 409 209 119 0.008 Boron (B) 2 18101** 49174** 107585** 0.050** Mepiquat chloride (M) 2 21456** 14021** 1146ns 0.374** Planting density (P) 1 56742** 113951** 274534** 0.065** B×M 4 91ns 698ns 569ns 0.004ns B×P 2 68ns 428ns 881ns 0.002ns

M×P 2 1491ns 27ns 994ns 0.003ns B×M×P 4 57ns 128ns 171ns 0.001ns Error 34 617 958 1273 0.009 Total 53

84


planting densities on vegetative dry matter (g m-2) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 448.41 396.17 424.32 422.97 C

600 ppm B 482.50 412.83 443.93 446.42 B

1200 ppm B 501.50 432.79 461.93 465.41 A

Mean (MC) 477.47 A 413.93 C 443.39 B


25 cm 15 cm

Control 382.47 463.46 422.97 C

600 ppm B 405.30 487.54 446.42 B

1200 ppm B 420.68 510.14 465.41 A

Mean (P) 402.82 B 487.04 A


at squaring

MC application

at flowering

Mean (B)

Control 502.13 440.06 466.37 469.52 C

600 ppm B 542.49 470.45 500.78 504.57 B

1200 ppm B 572.89 501.68 523.90 532.82 A

Mean (MC) 539.17 A 470.73 C 497.02 B


25 cm 15 cm

Control 439.32 499.72 469.52 C

600 ppm B 471.30 537.85 504.57 B

1200 ppm B 499.04 566.60 532.82 A

Mean (P) 469.89 B 534.72 A

85

Veg

eta

tiv

e d

ry

ma

tter (

g m

-2)

Figure 4.1: Influence of foliar applied mepiquat chloride and boron at various

planting densities on vegetative dry matter (g m-2) of cotton during 2014 (a) 25 cm

(b) 15 cm

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135

Control MC at squaring MC at flowering

Control 600 ppm boron 1200 ppm boron (a)

0.0

100.0

200.0

300.0

400.0

500.0

600.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135


Control 600 ppm boron 1200 ppm boron (b)

86

Veg

eta

tiv

e d

ry

ma

tter (

g m

-2)


planting densities on vegetative dry matter (g m-2) of cotton during 2015 (a) 25 cm

(b) 15 cm

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135


Control 600 ppm boron 1200 ppm boron

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



(a)

(b)

87

as compared to control, with highest dry matter accumulation in response to application of

1200 ppm B solution, during both years (Tables 4.49a, 4.50a). Conversely, mepiquat

chloride application decreased the vegetative dry matter accumulation (13%), as compared

to control, during both years. The least vegetative dry matter was produced when the cotton

plants were treated with mepiquat chloride at squaring stage (Tables 4.49a, 4.50a). In case

of planting densities, higher vegetative dry matter (14-21%) was recorded at higher planting

density, during both years (Tables 4.49b, 4.50b).

4.1.5.1.2. Reproductive dry matter

The periodic data indicated that that there was a linear increase in accumulation of

reproductive dry matter upto maturity (45-135 DAS), during both years. Cotton plants

accumulated higher reproductive dry matter by foliar B treatment, as compared to control.

The effect of foliar applied B in enhancing the reproductive dry matter accumulation was

increased with time until maturity, during both years. It was observed that reproductive dry

matter accumulated most actively during 90-105 DAS either with or without mepiquat

chloride at lower planting density during both years while at higher planting density during

2015. Whereas, during 2014 maximum reproductive dry matter was accumulated during

75-90 DAS at higher planting density and it was followed by 90-105 DAS (Figures 4.3,

4.4).

Reproductive dry matter production per m2 was improved by increasing the planting

density, during both years. The effect of foliar B on production of reproductive dry matter

was more pronounced at higher planting density as compared to lower planting density.

However, the effect of mepiquat chloride was more pronounced at higher planting density

during initial growth stages (upto 90 DAS) while at lower planting density at later growth

stages until maturity (90-135 DAS), during both years (Figures 4.3, 4.4).

Total reproductive dry matter was significantly affected by foliar applied B,

mepiquat chloride and planting density during both years, and interactive effect of B with

planting density during 2014. However, the interactive effect of B with mepiquat chloride,

mepiquat chloride with planting density and three way interaction among B, mepiquat

chloride and planting density was non-significant during both years (Tables 4.47, 4.48).

Foliar application of B improved the reproductive dry matter (18-20%), as compared to

control, with highest dry matter production occurring due to application of 1200 ppm boron,

during both years (Tables 4.51a, 4.52a). Likewise, the mepiquat chloride application

improved the reproductive dry matter (10-11%), as compared to control. Mepiquat chloride

application at squaring stage produced the highest reproductive dry matter, during both the

88


planting densities on reproductive dry matter (g m-2) of cotton (2014)







34.275.










at squaring

MC application

at flowering

Mean (B)

Control 517.32 573.33 546.56 545.74 C

600 ppm B 595.18 641.24 605.52 613.98 B

1200 ppm B 604.10 683.05 638.62 641.92 A

Mean (MC) 572.20 C 632.54 A 596.90 B


25 cm 15 cm

Control 487.50 e 603.98 c 545.74 C

600 ppm B 559.16 d 668.80 b 613.98 B

1200 ppm B 566.39 d 717.46 a 641.92 A

Mean (P) 537.68 B 663.41 A


at squaring

MC application

at flowering

Mean (B)

Control 487.21 524.69 512.48 508.13 C

600 ppm B 552.15 602.23 578.72 577.70 B

1200 ppm B 568.81 647.87 614.79 610.49 A

Mean (MC) 536.06 B 591.60 A 568.67 A


25 cm 15 cm

Control 465.04 551.22 508.13 C

600 ppm B 534.55 620.85 577.70 B

1200 ppm B 558.92 662.05 610.49 A

Mean (P) 519.50 B 611.38 A

89

Rep

ro

du

cti

ve d

ry

ma

tter (

g m

-2)


planting densities on reproductive dry matter (g m-2) of cotton during 2014 (a) 25

cm (b) 15 cm

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

900.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



(a)

90

Rep

ro

du

cti

ve d

ry

ma

tter (

g m

-2)


planting densities on reproductive dry matter (g m-2) of cotton during 2015 (a) 25

cm (b) 15 cm

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



(a)

(b)

91

years (Tables 4.51a, 4.52a). Moreover, the reproductive dry matter m-2 was increased by

increasing the planting density. However, application of B improved the dry matter at both

planting densities (19 and 16% at lower and higher planting density, respectively), as

compared to control. Highest reproductive dry matter was recorded by foliar application of

1200 ppm B at higher planting density (Tables 4.51b, 4.52b).

4.1.5.1.3. Total dry matter

The pattern of TDM showed a temporal increase, upto maturity (45-135 DAS),

during both years. Foliar application of B improved the TDM when compared with control

and the extent of improvement was increased with time, during both years. Mepiquat

chloride application did not impose any effect in improving the TDM production. It was

noticed that, highest TDM was accumulated during 90-105 DAS either under mepiquat

chloride treated or untreated plants, during both years. The planting densities altered the

TDM accumulation during both years. Moreover, foliar applied B improved the TDM

accumulation more when applied at higher planting density as compared to lower planting

density (Figures 4.5, 4.6).

Total dry matter significantly differed by the influence of foliar application of B

and planting density but the effect of mepiquat chloride, and interactive effect between B

and mepiquat chloride, B and planting density, mepiquat chloride and planting density and

interaction among B, mepiquat chloride and planting density was non-significant, during

both years (Tables 4.47, 4.48). The results revealed that B improved the TDM accumulation

and application of 1200 ppm B resulted in greatest improvement in TDM production (13-

16%), as compared to control during both years (Tables 4.53, 4.54). Moreover, increasing

the planting density than normal lead to increase in TDM production m-2 (15-22%), during

both years (Tables 4.53, 4.54).

4.1.5.1.4. Reproductive-vegetative dry matter ratio

The ratio of reproductive to vegetative dry matter was significantly affected by the

influence of B, mepiquat chloride and planting density. However, the interaction between

B and mepiquat chloride, B and planting density, mepiquat chloride and planting and three

way interaction among B, mepiquat chloride and planting density was non-significant

regarding reproductive-vegetative dry matter ratio, during both years (Tables 4.47, 4.48).

Foliar applied B exalted the reproductive to vegetative dry matter ratio, as compared to

control. The highest reproductive to vegetative dry matter ratio was recorded by the

influence of 1200 ppm B (1.46 and 1.21 during 2014 and 2015, respectively) and it was

followed by 600 ppm B (Tables 4.55a, 4.56a). Likewise, mepiquat chloride substantially

92


planting densities on total dry matter (g m-2) of cotton (2014)




planting densities on total dry matter (g m-2) of cotton (2015)




25 cm 15 cm

Control 863.28 1049.43 956.35 C

600 ppm B 950.57 1133.37 1041.97 B

1200 ppm B 968.89 1199.35 1084.12 A

Mean (P) 927.58 B 1127.38 A


25 cm 15 cm

Control 897.39 1031.13 964.26 C

600 ppm B 990.34 1125.67 1058.01 B

1200 ppm B 1038.26 1196.99 1117.62 A

Mean (P) 975.33 B 1117.93 A

93

To

tal

dry

ma

tter (

g m

-2)


planting densities on total dry matter (g m-2) of cotton during 2014 (a) 25 cm (b) 15

cm

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



94

To

tal

dry

ma

tter (

g m

-2)


planting densities on total dry matter (g m-2) of cotton during 2015 (a) 25 cm (b) 15

cm

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



95


planting densities on reproductive-vegetative dry matter ratio of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 1.18 1.49 1.34 1.34 B

600 ppm B 1.28 1.64 1.42 1.45 A

1200 ppm B 1.26 1.67 1.45 1.46 A

Mean (MC) 1.24 C 1.60 A 1.40 B


25 cm 15 cm

Control 1.30 1.37 1.34 B

600 ppm B 1.44 1.45 1.45 A

1200 ppm B 1.42 1.50 1.46 A

Mean (P) 1.39 B 1.44 A


at squaring

MC application

at flowering

Mean (B)

Control 1.00 1.23 1.13 1.12 B

600 ppm B 1.06 1.36 1.21 1.21 A

1200 ppm B 1.04 1.37 1.22 1.21 A

Mean (MC) 1.04 C 1.32 A 1.18 B


25 cm 15 cm

Control 1.09 1.16 1.12 B

600 ppm B 1.18 1.24 1.21 A

1200 ppm B 1.17 1.25 1.21 A

Mean (P) 1.15 B 1.22 A

96

improved the ratio of reproductive to vegetative dry matter, as compared to control. Highest

reproductive to vegetative dry matter ratio (1.60 and 1.32 during 2014 and 2015,

respectively) was recorded by application of mepiquat chloride at squaring stage (Tables

4.55a, 4.56a). Similarly, planting densities differed regarding reproductive to vegetative

dry matter ratio, during both years. Higher reproductive to vegetative dry matter ratio (1.44

and 1.22 during 2014 and 2015, respectively) was observed at higher planting density as

compared to lower planting density (Tables 4.55b, 4.56b).

4.1.5.2. Crop growth rate

The temporal pattern of CGR exhibited that CGR was first increased and then

declined with further increase in time upto maturity. Crop growth rate was enhanced by

foliar applied B, as compared to control. The extent of influence of B on CGR was

decreased with increase in time from 45 to 135 DAS at both planting densities, during both

years. The peak values of CGR were obtained between 90-105 DAS with or without

mepiquat chloride application at both planting densities, during both years. Initially, the

crop treated with mepiquat chloride at squaring stage exhibited less CGR (45-60 DAS) as

compared to control and then started increasing with increase in time (upto 90-105 DAS)

and afterwards declined (120-135 DAS). On the other hand, mepiquat chloride application

at flowering caused a decrease in CGR between 60-75 DAS, afterwards increased upto 90-

105 DAS, and then declined with further increase in time upto 120-135 DAS (Figures 4.7,

4.8).

Planting densities showed a differential pattern of CGR, during both years. Higher

CGR was observed at higher planting density during initial growth stages while decreased

at later growth stages as compared to lower planting density, during both years. Likewise,

influence of B and mepiquat chloride in increasing and decreasing the CGR, respectively,

was higher at higher planting density during early growth stages while later on opposite

was observed (Figures 4.7, 4.8).

The effect of foliar B and planting density on mean CGR was significant while

effect of mepiquat chloride, and interactive effects of B with mepiquat chloride, B with

planting density, mepiquat chloride with planting density as well as three way interaction

among B, mepiquat chloride and planting density was non-significant during both years

(Tables 4.57, 4.58). The CGR was improved by B application (15-19%), as compared to

control and 1200 ppm B caused maximum increase (Tables 4.59, 4.60). On the other hand,

higher mean CGR (10-17%) was recorded at higher planting density, during both years

(Tables 4.59, 4.60).

97

4.1.5.3. Leaf area and leaf area index

The temporal pattern of leaf area and LAI depicted a sharp increase with a decline

with advancement of maturity, during both years. Higher leaf area and LAI was produced

by B application, as compared to control. It was observed that there was a linear increase

in leaf area and LAI upto 120 DAS after which a decline occurred (135 DAS), during both

years. The mepiquat chloride application at different growth stages affected the leaf area

and LAI differently. Mepiquat chloride application at squaring caused a reduction in leaf

area and LAI at earlier growth stages (45 DAS) while mepiquat chloride application at

flowering reduced leaf area and LAI at 75 DAS and then started increasing afterwards. The

peak values of leaf area and LAI were recorded at 120 DAS (Figures 9-12).

The planting densities differed in their effect on leaf area and LAI during both years.

It was observed that higher leaf area was recorded at lower planting density while higher

LAI was noticed at higher planting density. Moreover, the effect of B and mepiquat chloride

on leaf area as well as LAI was more pronounced at higher planting density, during both

years (Figures 9-12).

Maximum LAI (120 DAS) was significantly affected by foliar applied B, mepiquat

chloride and planting density; however, the interactive effect between B and mepiquat

chloride, B and planting density, mepiquat chloride and planting density as well as three

way interaction among B, mepiquat chloride and planting density was non-significant,

during both years (Tables 4.57, 4.58). Leaf area index was increased by B application with

maximum LAI (3.79 and 4.05 during 2014 and 2015, respectively) produced by 1200 ppm

B (Tables 4.61a, 4.62a). On the other hand, mepiquat chloride application decreased the

LAI. Lowest LAI (3.38 and 3.66 during 2014 and 2015, respectively) was recorded by

application of mepiquat chloride at squaring stage (Tables 4.61a, 4.62a). Whereas, higher

LAI (3.98 and 4.34 during 2014 and 2015, respectively) was noticed by sowing the crop at

higher planting density, during both years (Tables 4.61b, 4.62b).

4.1.5.4. Leaf area duration

Leaf area duration significantly differed by the influence of B, mepiquat chloride

and planting density but the interactive effect between B and mepiquat chloride, B and

planting density, mepiquat chloride and planting density as well as interaction among B,

mepiquat chloride and planting density was non-significant, during both years (Tables 4.57,

4.58). Leaf area duration was improved by foliar application of B, as compared to control

during both years. Maximum value of LAD (243 and 261 days during 2014 and 2015,

respectively) was recorded by application of 1200 ppm B (Tables 4.63a, 4.64a). On the

98








Mean sum of squares

Crop growth

rate

Leaf area

index

Leaf area

duration

Net

assimilation

rate

Replications 2 0.178 0.007 81.5 0.013 Boron (B) 2 9.045** 0.541** 2502.0** 0.137ns Mepiquat chloride (M) 2 0.080ns 1.139** 6113.5** 1.458** Planting density (P) 1 32.449** 7.099** 48097.3** 0.647** B×M 4 0.087ns 0.005ns 19.2ns 0.006ns B×P 2 0.371ns 0.022ns 58.2ns 0.041ns M×P 2 0.026ns 0.020ns 173.2ns 0.007ns B×M×P 4 0.020ns 0.005ns 16.5ns 0.001ns

Error 34 0.161 0.029 128.1 0.058 Total 53


Mean sum of squares

Crop growth

rate

Leaf area

index

Leaf area

duration

Net

assimilation

rate

Replications 2 0.063 0.002 117.9 0.081 Boron (B) 2 12.553** 0.520** 2865.9** 0.337ns Mepiquat chloride (M) 2 0.053ns 0.985** 5715.9** 0.805** Planting density (P) 1 11.408** 10.872** 74881.4** 10.323** B×M 4 0.079ns 0.004ns 10.1ns 0.030ns B×P 2 0.106ns 0.019ns 152.8ns 0.062ns M×P 2 0.099ns 0.014ns 122.9ns 0.031ns

B×M×P 4 0.024ns 0.001ns 51.4ns 0.024ns Error 34 0.181 0.032 81.5 0.130 Total 53

99


planting densities on mean crop growth rate (g m-2 d-1) of cotton (2014)




planting densities on mean crop growth rate (g m-2 d-1) of cotton (2015)




25 cm 15 cm

Control 8.31 9.73 9.02 C

600 ppm B 9.27 10.62 9.95 B

1200 ppm B 9.48 11.35 10.42 A

Mean (P) 9.02 B 10.57 A


25 cm 15 cm

Control 8.54 9.39 8.97 C

600 ppm B 9.57 10.38 9.98 B

1200 ppm B 10.07 11.17 10.62 A

Mean (P) 9.40 B 10.31 A

100

Cro

p g

ro

wth

ra

te (

g m

-2 d

-1)


planting densities on crop growth rate (g m-2 d-1) of cotton during 2014 (a) 25 cm (b)

15 cm

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5



0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5



101

Cro

p g

ro

wth

ra

te (

g m

-2 d

-1)


planting densities on crop growth rate (g m-2 d-1) of cotton during 2015 (a) 25 cm

(b) 15 cm

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5



0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5



102


planting densities on leaf area index of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 3.68 3.22 3.44 3.44 C

600 ppm B 3.90 3.37 3.55 3.61 B

1200 ppm B 4.05 3.54 3.78 3.79 A

Mean (MC) 3.88 A 3.38 C 3.59 B


25 cm 15 cm

Control 3.11 3.77 3.44 C

600 ppm B 3.25 3.97 3.61 B

1200 ppm B 3.39 4.19 3.79 A

Mean (P) 3.25 B 3.98 A


at squaring

MC application

at flowering

Mean (B)

Control 3.95 3.46 3.73 3.71 C

600 ppm B 4.14 3.69 3.87 3.90 B

1200 ppm B 4.29 3.83 4.04 4.05 A

Mean (MC) 4.13 A 3.66 C 3.88 B


25 cm 15 cm

Control 3.30 4.13 3.71 C

600 ppm B 3.45 4.35 3.90 B

1200 ppm B 3.57 4.54 4.05 A

Mean (P) 3.44 B 4.34 A

103

Lea

f a

rea

(cm

2)


planting densities on leaf area (cm2) of cotton during 2014 (a) 25 cm (b) 15 cm

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



104

Lea

f a

rea

(cm

2)


planting densities on leaf area (cm2) of cotton during 2015 (a) 25 cm (b) 15 cm

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135


Control 600 ppm boron 1200 ppm boron (a

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



105

Lea

f a

rea

in

dex


planting densities on leaf area index of cotton during 2014 (a) 25 cm (b) 15 cm

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



106

Lea

f a

rea

in

dex


planting densities on leaf area index of cotton during 2015 (a) 25 cm (b) 15 cm

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



0.0

1.0

2.0

3.0

4.0

5.0

6.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



107


planting densities on leaf area duration (days) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 249.28 215.71 232.30 232.43 C

600 ppm B 266.26 227.95 243.09 245.77 B

1200 ppm B 275.69 237.19 254.94 255.94 A

Mean (MC) 263.74 A 226.95 C 243.44 B


25 cm 15 cm

Control 204.25 260.61 232.43 C

600 ppm B 216.16 275.37 245.77 B

1200 ppm B 224.19 287.69 255.94 A

Mean (P) 214.87 B 274.56 A


at squaring

MC application

at flowering

Mean (B)

Control 266.11 231.13 249.64 248.96 C

600 ppm B 280.93 245.54 260.14 262.21 B

1200 ppm B 292.46 255.93 274.18 274.19 A

Mean (MC) 279.83 A 244.20 C 261.32 B


25 cm 15 cm

Control 214.72 283.20 248.96 C

600 ppm B 224.78 299.64 262.21 B

1200 ppm B 234.13 314.24 274.19 A

Mean (P) 224.55 B 299.02 A

108

other hand, mepiquat chloride application decreased the LAD, as compared to control

during both years. Minimum LAD (246 and 262 days during 2014 and 2015, respectively)

was recorded when mepiquat chloride was applied at squaring stage (Tables 4.63a, 4.64a).

However, LAD was higher (275 and 299 days during 2014 and 2015, respectively) at higher

planting density as compared to lower planting density, during both years (Tables 4.63b,

4.64b).

4.1.5.5. Net assimilation rate

Foliar applied mepiquat chloride and planting density significantly affected the

NAR however, the effect of B and interactions of B with mepiquat chloride, B with planting

density, mepiquat chloride and planting density, as well as three way interaction among B,

mepiquat chloride and planting density was non-significant, during both years (Tables 4.57,

4.58). It was observed that application of B improved the NAR (2-4%) non-significantly,

as compared to control. However, application of mepiquat chloride significantly enhanced

the NAR, as compared to control during both years. Highest increase in NAR (6-8%) was

recorded by application of mepiquat chloride at squaring stage and it was followed by

application of mepiquat chloride at flowering stage (Tables 4.65, 4.66). On the other hand,

NAR decreased at higher planting density (3-13%) as compared to lower planting density,

during both years (Tables 4.65, 4.66).

4.1.6. Discussion

The results revealed that foliar application of B improved the vegetative,

reproductive and total dry matter, whereas, mepiquat chloride reduced vegetative dry

matter accumulation, increased the reproductive dry matter while imposed no effect on

TDM, at both planting densities. However, both B and mepiquat chloride improved the

reproductive-vegetative dry matter ratio, as compared to control, at both planting densities.

The improvement in dry matter production and dry matter partitioning by foliage applied

B might be attributed to improved rate of photosynthesis. It has been observed that B

application improves the leaf chlorophyll content, stomatal conductance, intercellular CO2

concentration, transpiration rate and rate of photosynthesis (Ahmed et al., 2014). Similarly,

Qiong et al. (2002) described that application of B improved the photosynthetic rate in

peanut which consequently increased the dry matter accumulation. Similar increase in dry

matter production of cotton by B application has been reported by (Rosolem and Costa,

2000; Fontes et al., 2008; Ahmed et al., 2011).

Mepiquat chloride application did not affect the TDM production as compared to

control, rather the dry matter was first decreased immediately after its application and then

109


planting densities on mean net assimilation rate (g m-2 d-1) of cotton (2014)


density, B: Boron; HSD for P = 0.1330, HSD for MC = 0.1967.


planting densities on mean net assimilation rate (g m-2 d-1) of cotton (2015)


density, B: Boron; HSD for P = 0.1991, HSD for MC = 0.2944.


25 cm 15 cm

Control 7.02 6.82 6.92 B

MC application at squaring 7.57 7.38 7.47 A

MC application at flowering 7.23 6.96 7.09 B

Mean (P) 7.27 A 7.05 B


25 cm 15 cm

Control 7.30 6.50 6.90 B

MC application at squaring 7.76 6.89 7.33 A

MC application at flowering 7.58 6.62 7.10 AB

Mean (P) 7.55 A 6.67 B

110

again started increasing with advancement of crop growth. The decrease in dry matter by

mepiquat chloride was associated with decrease in vegetative growth that lead to decrease

in vegetative dry matter production. However, with the passage of time the plants started

regaining the vegetative growth that led to increase in vegetative dry matter and TDM

accumulation. Moreover, at latter growth stages there was a sudden increase in reproductive

growth and reproductive dry matter that balanced the TDM and equalized it to TDM of

control plants. Similar, results have been reported by Zhao and Oosterhuis (2000), de-

Almeida and Rosolem (2012), Gonias et al. (2012) and Mao et al. (2014) that mepiquat

chloride did not affect the TDM significantly.

In this study reproductive-vegetative dry matter ratio was improved by foliar

application of B indicating enhanced dry matter partitioning to the reproductive growth.

This might be attributed to enhanced fruit retention at lower sympodial branches and distal

positions at sympodial branches which led to earlier shift of balance to reproductive growth

with subsequent decrease in vegetative growth. Similar results were reported by (Zhao and

Oosterhuis, 2002) that B application enhanced the partitioning of photo-assimilates to the

reproductive structures. Likewise, in present study mepiquat chloride improved the dry

matter partitioning to reproductive parts. Similar, results have been reported by Zhao and

Oosterhuis (2000), Gonias et al. (2012) and Mao et al. (2014) that mepiquat chloride

improved the dry matter partitioning to the reproductive growth and it was attributed to

shift in balance from vegetative to reproductive growth. In this study, it was observed that

increasing the planting density enhanced the vegetative, reproductive and total dry matter

production per m2, as well as reproductive-vegetative dry matter ratio. This indicates that

enhancing the planting density resulted in an increase in dry matter partitioning from

vegetative to reproductive growth. This is attributed to earlier initiation of reproductive

growth which led to enhanced dry matter partitioning to the reproductive growth. Similar,

results were reported by Ali et al. (2009a), Wang et al. (2011) and Kaggwa-Asiimwe et al.

(2013) that increasing the planting density increased the TDM accumulation per unit area

with an enhanced dry matter partitioning to the reproductive structures.

Crop growth rate exhibited similar trend as was observed for TDM accumulation.

It was observed that B application enhanced the mean CGR while mepiquat chloride

decreased the CGR, as compared to control. Whereas, higher mean CGR was recorded at

higher planting density.

In this study, it was observed that LAD was enhanced by foliar application of B

while decreased by mepiquat chloride application. On the other hand, higher planting

111

density exhibited higher LAD, as compared to lower planting density. Leaf area duration

corresponds to the duration for which the assimilatory structures remain active. Higher

LAD of cotton by B application is attributed to higher leaf area and LAI. Leaf area is

important in terms of photosynthetic surface. It has been observed that higher the leaf area

higher will be the photosynthetic surface that consequently results in higher dry matter

accumulation. Similar results were reported by Zhao and Oosterhuis (2003) that B

improved the leaf area and rate of leaf net photosynthesis ultimately improving the dry

matter accumulation. However, mepiquat chloride application decreased the LAD which

was associated with lower leaf area and LAI. However, the dry matter accumulation and

CGR were least affected by mepiquat chloride despite of lower LAD. It might be attributed

to improved photosynthetic rate, higher specific leaf area and higher reproductive growth

in response to mepiquat chloride (Zhao and Oosterhuis, 2000). Increasing the planting

density resulted in a decrease in leaf area while increased the LAI and LAD. Similarly,

Kaggwa-Asiimwe et al. (2013) reported that LAI was increased with increasing planting

density.

The NAR was significantly enhanced by mepiquat chloride while foliar applied B

improved the NAR non-significantly. However, increasing the planting density caused a

reduction in NAR. The enhanced NAR by mepiquat chloride might be attributed to

enhanced photosynthetic rate with lower assimilatory surface. The improvement in

photosynthetic rate might be supported by enhanced chlorophyll contents and improved

light penetration within plant canopy (Gonias et al., 2012). However, the non-significant

improvement in NAR by B application might also be associated with enhanced

photosynthetic rate due to improved leaf area and leaf chlorophyll contents. On the other

hand, decrease in NAR by increasing the planting density may be explained by the fact that

high planting density decreases the biosynthesis of photosynthetic pigments along with a

decrease in rate of photosynthesis. However, in this study the dry matter accumulation per

unit area was increased at higher planting density while NAR was decreased. This might

be because the increase in planting density decreases the leaf area per plant that results in

a decrease in photosynthetic rate on per plant basis. However, the dry matter accumulation

per unit area is increased because of high LAI.

4.1.7. Boll distribution pattern

The proportion of bolls at first position was significantly affected by increasing the

planting density; however, the effect of foliar applied B and mepiquat chloride, and

interactions between B and mepiquat chloride, B and planting density, mepiquat chloride

112

and planting density, and three way interaction of B, mepiquat chloride and planting density

was non-significant, during both years (Tables 4.67, 4.68). The proportion of bolls at

second position was significantly affected by B, mepiquat chloride and planting density but

the interactive effects of B with mepiquat chloride, B with planting density, mepiquat

chloride with planting density and three way interaction among B, mepiquat chloride and

plating density was non-significant, during both years (Tables 4.67, 4.68). The proportion

of bolls at outer sympodial positions significantly differed by the influence of B, mepiquat

chloride, planting density and interaction between B and mepiquat chloride. However, the

interactive effect of B with mepiquat chloride, mepiquat chloride with planting density and

three way interaction of B, mepiquat chloride and planting density was non-significant


The percent of first position bolls at sympodial branches was remained unaffected

by foliar B and mepiquat chloride application while higher percent of first position bolls

(≈72 and 71% during 2014 and 2015, respectively) was observed at higher planting density,

during both the years (Tables 4.69, 4.70). The percent of second position bolls was

decreased by foliar application of B with lowest percentage of second position bolls (≈21%

during both years) occurring by application of 1200 ppm B solution. However, the effect

of 600 ppm B solution was at par during both years (Tables 4.71a, 4.72a). Likewise,

application of mepiquat chloride decreased the proportion of second position bolls, as

compared to control during both years. Treatment with mepiquat chloride at squaring stage

produced the least percent of bolls at second position (≈22% during both years) but the

effect of mepiquat chloride application at flowering stage was statistically similar during

both years (Tables 4.71a, 4.72a). However, increasing the planting density positively

influenced the proportion of bolls at second position. It was noticed that higher proportion

of bolls at second position (≈23%) was occurred at higher planting density, during both

years (Tables 4.71b, 4.72b).

The percent of outer position bolls was interactively increased by foliar application

of B and mepiquat chloride as compared to control, during both years. Foliar application of

1200 ppm B solution in combination with mepiquat chloride at squaring stage produced the

highest percentage of outer position bolls (≈7 and 9% during 2014 and 2015, respectively).

However, the effect of 600 ppm B in combination with mepiquat chloride at squaring stage

during both years and 1200 ppm B in combination with mepiquat chloride at flowering

stage during 2015 was statistically similar (Tables 4.735a, 4.74a). In case of planting

density lesser proportion of bolls at outer sympodial positions (≈5 and 6% during 2014 and

113


boron at various planting densities on boll distribution pattern at sympodial branches

of cotton (2014)



boron at various planting densities on boll distribution pattern at sympodial branches

of cotton (2015)



Mean sum of squares

1st position

bolls

2nd position

bolls

Outer

position

bolls

Replications 2 1.396 1.115 0.022

Boron (B) 2 6.495ns 15.139* 1.804**

Mepiquat chloride (M) 2 6.852ns 17.445** 2.435**

Planting density (P) 1 28.616** 30.842** 118.845**

B×M 4 1.098ns 1.318ns 0.308*

B×P 2 0.560ns 1.088ns 0.123ns

M×P 2 0.034ns 0.051ns 0.053ns

B×M×P 4 0.269ns 0.605ns 0.090ns

Error 34 3.140 2.633 0.090

Total 53


Mean sum of squares

1st position

bolls

2nd position

bolls

Outer

position

bolls

Replications 2 6.285 4.112 0.283

Boron (B) 2 7.403ns 18.688** 2.567**

Mepiquat chloride (M) 2 5.631ns 18.556** 3.740**

Planting density (P) 1 50.113** 34.961** 168.82**

B×M 4 0.126ns 0.582ns 0.220*

B×P 2 1.061ns 1.785ns 0.113ns

M×P 2 0.005ns 0.073ns 0.040ns

B×M×P 4 0.463ns 0.551ns 0.013ns

Error 34 2.874 2.410 0.080

Total 53

114


planting densities on percent of first position bolls (%) of cotton (2014)




planting densities on percent of first position bolls (%) of cotton (2015)




planting densities on percent of second position bolls (%) of cotton (2014)








25 cm 15 cm

Control 70.32 71.86 71.09

600 ppm B 71.33 72.39 71.86

1200 ppm B 71.39 73.15 72.27

Mean (P) 71.01 B 72.47 A


25 cm 15 cm

Control 68.65 70.18 69.41

600 ppm B 69.35 71.13 70.24

1200 ppm B 69.44 71.91 70.68

Mean (P) 69.15 B 71.07 A


at squaring

MC application

at flowering

Mean (B)

Control 24.32 21.91 22.73 23.00 A

600 ppm B 22.18 21.21 21.95 21.78 AB

1200 ppm B 22.46 19.94 21.17 21.19 B

Mean (MC) 23.00 A 21.02 B 21.95 AB


25 cm 15 cm

Control 22.35 23.63 23.00 A

600 ppm B 20.74 22.82 21.78 AB

1200 ppm B 20.60 21.78 21.19 B

Mean (P) 21.23 B 22.74 A

115










planting densities on percent of outer position bolls (%) of cotton (2014)


chloride, B: Boron; HSD for MC = 0.2445, HSD for B = 0.2445, HSD for MC×B = 0.5716.






at squaring

MC application

at flowering

Mean (B)

Control 23.85 22.32 23.01 23.06 A

600 ppm B 22.70 20.88 21.63 21.74 B

1200 ppm B 22.49 19.78 20.89 21.06 B

Mean (MC) 23.02 A 20.99 B 21.84 AB


25 cm 15 cm

Control 22.03 24.09 23.06 A

600 ppm B 20.80 22.68 21.74 B

1200 ppm B 20.61 21.50 21.06 B

Mean (P) 21.15 B 22.76 A


at squaring

MC application

at flowering

Mean (B)

Control 5.65 d 6.05 cd 6.06 cd 5.92 B

600 ppm B 6.07 cd 6.66 ab 6.36 bc 6.36 A

1200 ppm B 5.95 cd 7.16 a 6.50 bc 6.54 A

Mean (MC) 5.89 C 6.62 A 6.31 B


25 cm 15 cm

Control 7.33 4.51 5.92 B

600 ppm B 7.93 4.79 6.36 A

1200 ppm B 8.01 5.07 6.54 A

Mean (P) 7.76 A 4.79 B

116











at squaring

MC application

at flowering

Mean (B)

Control 7.16 d 7.82 c 7.60 cd 7.53 C

600 ppm B 7.66 cd 8.39 ab 8.01 bc 8.02 B

1200 ppm B 7.54 cd 8.87 a 8.39 ab 8.27 A

Mean (MC) 7.45 C 8.36 A 8.00 B


25 cm 15 cm

Control 9.32 5.73 7.53 C

600 ppm B 9.85 6.19 8.02 B

1200 ppm B 9.95 6.59 8.27 A

Mean (P) 9.71 A 6.17 B

117

2015, respectively) was observed at higher planting density (Tables 4.735b, 4.74b).

4.1.8. Discussion

A differential spatial horizontal distribution of bolls on sympodial branches was

observed by the influence of foliar applied B, mepiquat chloride and planting density.

Boron as well as mepiquat chloride application did not, affect percent of first position,

decreased the percent of second position bolls while significantly interacted in increasing

the percent of outer position bolls at sympodial branches across both planting densities.

This indicates that the B and mepiquat chloride increases the boll load by increasing the

fruiting positions and boll retention at distal positions. This might be due to the enhanced

photosynthesis and assimilate translocation from source to sink by foliar application of B

and mepiquat chloride. It has been observed that boron deficiency is associated with

decrease in photosynthesis, dry matter partitioning, fruiting sites and fruit retention (Zhao

and Oosterhuis, 2003; Ahmed et al., 2014). Whereas, mepiquat chloride decreases the

vegetative growth and makes the photo-assimilates available for reproductive growth;

moreover, it improves the light penetration and distribution within plant canopy which

assists in the greater boll retention at lower sympodial branches (Zhao and Oosterhuise,

2000; Gonias et al., 2012; Mao et al., 2015). Gwathmey and Clement (2010) reported that

mepiquat chloride increased the boll retention at lower and middle sympodial branches

while decreased at upper branches; however, it did not affect the first position bolls.

Planting density concentrated the bolls at first and second positions relative to lower

planting density while decreased the percent of outer position bolls. This indicates that the

plants in higher planting density produced shorter sympodial branches with fewer fruiting

positions and also for less time as compared to plants in lower planting density. These

results are in accordance with Gwathmey and Clement (2010) who reported that high boll

load was occurred at first and second positions at higher planting density due to more

competition for resources.


The plants m-2 were significantly affected by planting density; however, the effect

of B, mepiquat chloride and planting density as well as the interactions between B and

mepiquat chloride, B and planting density, mepiquat chloride and planting density, and

three way interaction among B, mepiquat chloride and planting density was non-significant,

during both years (Tables 4.75, 4.76). The number of opened bolls per plant and per m2,

and total bolls per plant were significantly affected by B, mepiquat chloride, planting

density and the interaction of B with mepiquat chloride and B with planting density, while,

118

the interactive effect of mepiquat chloride with planting density and three way interaction

among B, mepiquat chloride and planting density was non-significant, during both years

(Tables 4.75, 4.76).

Effect of foliar applied B and planting density on number of unopened bolls per

plant was significant during both years while the effect of mepiquat chloride was significant

during 2014 only. Furthermore the interactive effect of B with mepiquat chloride, B with

planting density, mepiquat chloride with planting density and three way interaction among

B, mepiquat chloride and planting density was non-significant, during both years (Tables

4.75, 4.76). The average boll weight was significantly affected by B, mepiquat chloride,

planting density and interaction between B and mepiquat chloride. Nonetheless, the

interactive effect of B with planting density, mepiquat chloride with planting density and

three way interaction among B, mepiquat chloride and planting density was non-significant,


The number of plants m-2 was increased by decreasing the intra-row plant spacing,

during both years (Tables 4.77, 4.78). The number of opened bolls per plant and m -2, and

total bolls per plant were increased by application of B and mepiquat chloride, as compared

to control; however, application of B in combination with mepiquat chloride caused more

increase, as compared to their sole application, during both years. The greatest increase in

number of opened bolls per plant (31-32%), boll density (30-31%) and total number bolls

per plant (26-28%) was caused by foliar application of 1200 ppm B in combination with

mepiquat chloride application at squaring stage during both years. However, application of

600 ppm B in combination with mepiquat chloride application at squaring stage produced

statistically similar results for number of opened bolls per plant and total bolls per plant

during both years; while, application of 1200 ppm B in combination with mepiquat chloride

application at flowering produced similar results for these traits during 2014 (Tables 4.79a-

4.82a, 4.85a, 4.86a). It was observed that increasing the planting density decreased the

number of opened and total bolls per plant while increased the boll density. Foliar

application of B at both planting densities improved the number of opened bolls per plant

(11-14 and 14-16% at lower and higher planting density, respectively), total number of

bolls per plant (11-13 and 13-15% at lower and higher planting density, respectively), as

well as boll density (11-15 and 14-15% at lower and higher planting density, respectively),

as compared to their respective controls. The greatest number of opened bolls per plant and

total bolls per plant were occurred by foliar application of 1200 ppm B at lower planting

density, while the effect of 600 ppm B at lower planting density was statistically similar,

119

Table 4.75: Analysis of variance for influence of foliar applied mepiquat chloride and boron

at various planting densities on yield related attributes of cotton (2014)



at various planting densities on yield related attributes of cotton (2015)


Table 4.77: Influence of foliar applied mepiquat chloride and boron at various planting

densities on number of plants m-2

of cotton (2014)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; P: Planting density, B: Boron; HSD for P = 0.1972.


densities on number of plants m-2

of cotton (2015)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; P: Planting density, B: Boron; HSD for P = 0.1972.


Mean sum of squares

Plants

m-2

Opened

bolls per

plant

Opened

bolls m-2

Unopene

d bolls

per plant

Total bolls

per plant

Boll

weight

Replications 2 0.500 1.091 74.7 0.024 1.340 0.007

Boron (B) 2 0.042ns 30.016** 1106.8** 0.181** 34.790** 0.422**

Mepiquat chloride (M) 2 0.014ns 40.527** 1708.5** 0.1134* 40.675** 0.277**

Planting density (P) 1 153.352** 341.009** 10514.4** 7.223** 447.494** 1.450**

B×M 4 0.056ns 2.895* 91.5* 0.021ns 3.040* 0.029*

B×P 2 0.144ns 3.645* 151.4* 0.010ns 4.034* 0.011ns

M×P 2 0.005ns 0.590ns 50.9ns 0.012ns 0.623ns 0.004ns

B×M×P 4 0.046ns 0.463ns 10.3ns 0.008ns 0.552ns 0.004ns

Error 34 0.127 0.942 30.0 0.028 1.004 0.010

Total 53


Mean sum of squares

Plants

m-2

Opened

bolls per

plant

Opened

bolls m-2

Unopened

bolls per

plant

Total

bolls per

plant

Boll

weight

Replications 2 0.500 0.514 57.84 0.026 0.663 0.005

Boron (B) 2 0.042ns 25.010** 1042.63** 0.103* 28.171** 0.272**

Mepiquat chloride (M) 2 0.014ns 23.656** 950.30** 0.024ns 24.267** 0.221**

Planting density (P) 1 153.35** 453.560** 1797.47** 5.320** 557.128** 0.507**

B×M 4 0.056ns 1.557* 76.20** 0.003ns 1.501* 0.042*

B×P 2 0.144ns 1.918* 54.21* 0.003ns 1.935* 0.004ns

M×P 2 0.005ns 0.334ns 19.66ns 0.0001ns 0.335ns 0.002ns


Error 34 0.127 0.557 18.24 0.024 0.496 0.014

Total 53


25 cm 15 cm

Control 5.15 8.18 6.66

600 ppm B 5.10 8.17 6.63

1200 ppm B 5.11 8.07 6.59

Mean (P) 5.12 B 8.14 A


25 cm 15 cm

Control 5.22 8.06 6.64

600 ppm B 5.23 8.07 6.65

1200 ppm B 5.22 8.07 6.65

Mean (P) 5.22 B 8.07 A

120


planting densities on number of opened bolls per plant of cotton (2014)








1.3805.










1.0616.


at squaring

MC application

at flowering

Mean (B)

Control 17.83 e 19.92 cd 18.87 de 18.87 C

600 ppm B 19.42 de 21.83 abc 20.33 bcd 20.53 B

1200 ppm B 19.00 de 23.50 a 21.75 ab 21.42 A

Mean (MC) 18.75 C 21.75 A 20.32 B


25 cm 15 cm

Control 21.19 b 16.56 d 18.87 C

600 ppm B 23.56 a 17.50 d 20.53 B

1200 ppm B 23.61 a 19.22 c 21.42 A

Mean (P) 22.79 A 17.76 B


at squaring

MC application

at flowering

Mean (B)

Control 15.63 e 16.96 de 16.46 de 16.35 C

600 ppm B 16.79 de 19.13 ab 17.50 cd 17.81 B

1200 ppm B 17.04 de 20.25 a 18.75 bc 18.68 A

Mean (MC) 16.49 C 18.78 A 17.57 B


25 cm 15 cm

Control 18.92 b 13.78 d 16.35 C

600 ppm B 21.03 a 14.58 d 17.81 B

1200 ppm B 21.58 a 15.78 c 18.68 A

Mean (P) 20.51 A 14.71 B

121


planting densities on number of opened bolls per m-2 of cotton (2014)








7.7890.










6.0759.


at squaring

MC application

at flowering

Mean (B)

Control 115.05 d 130.61 bc 120.96 cd 122.20 C

600 ppm B 124.61 cd 139.42 b 130.17 bc 131.40 B

1200 ppm B 123.20 cd 151.25 a 138.96 b 137.80 A

Mean (MC) 120.95 C 140.42 A 130.03 B


25 cm 15 cm

Control 109.02 d 135.39 b 122.20 C

600 ppm B 119.88 c 142.92 b 131.40 B

1200 ppm B 120.64 c 154.96 a 137.80 A

Mean (P) 116.51 B 144.42 A


at squaring

MC application

at flowering

Mean (B)

Control 100.06 d 108.41 c 105.86 cd 104.77 C

600 ppm B 107.91 cd 121.87 b 111.47 c 113.75 B

1200 ppm B 109.22 c 130.47 a 120.03 b 119.91 A

Mean (MC) 105.73 C 120.25 A 112.45 B


25 cm 15 cm

Control 98.66 d 110.89 c 104.77 C

600 ppm B 109.86 c 117.64 b 113.75 B

1200 ppm B 112.60 bc 127.22 a 119.91 A

Mean (P) 107.04 B 118.58 A

122


planting densities on number of unopened bolls per plant of cotton (2014)












planting densities on total number of bolls per plant of cotton (2014)





at squaring

MC application

at flowering

Mean (B)

Control 2.98 3.05 3.12 3.05 B

600 ppm B 3.22 3.13 3.26 3.20 A

1200 ppm B 3.16 3.17 3.39 3.24 A

Mean (MC) 3.12 B 3.12 B 3.26 A


25 cm 15 cm

Control 3.41 2.69 3.05 B

600 ppm B 3.59 2.81 3.20 A

1200 ppm B 3.58 2.89 3.24 A

Mean (P) 3.53 A 2.80 B


25 cm 15 cm

Control 3.20 2.57 2.89 B

600 ppm B 3.33 2.69 3.01 AB

1200 ppm B 3.32 2.72 3.02 A

Mean (P) 3.29 A 2.66 B


at squaring

MC application

at flowering

Mean (B)

Control 20.82 d 22.97 c 21.98 cd 21.92 C

600 ppm B 22.63 cd 24.97 ab 23.59 bc 23.73 B

1200 ppm B 22.16 cd 26.67 a 25.14 ab 24.66 A

Mean (MC) 21.87 C 24.87 A 23.57 B

123





1.4256.










1.0019.


planting densities on average boll weight (g) of cotton (2014)





25 cm 15 cm

Control 24.60 b 19.24 d 21.92 C

600 ppm B 27.15 a 20.31 d 23.73 B

1200 ppm B 27.19 a 22.12 c 24.66 A

Mean (P) 26.31 A 20.56 B


at squaring

MC application

at flowering

Mean (B)

Control 18.45 e 19.86 d 19.39 d 19.23 C

600 ppm B 19.79 de 22.12 ab 20.54 cd 20.82 B

1200 ppm B 20.03 de 23.27 a 21.81 bc 21.70 A

Mean (MC) 19.42 C 21.75 A 20.58 B


25 cm 15 cm

Control 22.12 b 16.34 d 19.23 C

600 ppm B 24.36 a 17.27 d 20.82 B

1200 ppm B 24.91 a 18.50 c 21.70 A

Mean (P) 23.80 A 17.37 B


at squaring

MC application

at flowering

Mean (B)

Control 2.70 c 2.81 c 2.80 c 2.77 B

600 ppm B 2.83 bc 3.13 a 3.01 ab 2.99 A

1200 ppm B 2.87 bc 3.13 a 3.18 a 3.06 A

Mean (MC) 2.80 B 3.03 A 3.00 A

124















25 cm 15 cm

Control 2.92 2.62 2.77 B

600 ppm B 3.18 2.80 2.99 A

1200 ppm B 3.21 2.91 3.06 A

Mean (P) 3.10 A 2.78 B


at squaring

MC application

at flowering

Mean (B)

Control 2.75 c 2.87 c 2.85 c 2.82 B

600 ppm B 2.87 c 3.16 ab 2.95 bc 2.99 A

1200 ppm B 2.88 c 3.12 ab 3.19 a 3.06 A

Mean (MC) 2.84 B 3.05 A 3.00 A


25 cm 15 cm

Control 2.92 2.73 2.82 B

600 ppm B 3.10 2.88 2.99 A

1200 ppm B 3.15 2.98 3.06 A

Mean (P) 3.06 A 2.86 B

125

during both years (Tables 4.79b, 4.80b, 4.85b, 4.86b). However, highest boll density was

observed by application of 1200 ppm B at higher planting density, during both years

(Tables 4.81b, 4.82b). The number of unopened bolls per plant was increased by application

of 1200 ppm B but the effect of 600 ppm B was statistically similar during both years

(Tables 4.83a, 4.84). On the other hand, application of mepiquat chloride at flowering stage

produced highest number of unopened bolls during 2014 while there was no effect of

mepiquat chloride during 2015 (Table 4.83a). In case of planting density the less number

of unopened bolls were produced at higher planting density as compared to lower planting

density, during both years (Tables 4.83b, 4.84).

Application of B and mepiquat chloride enhanced the average boll weight during

both years, as compared to control. Greatest increase in boll weight (16-18%) was recorded

by application of 1200 ppm B when applied in combination with mepiquat chloride at

flowering stage during both years; however the effect of 1200 ppm B in combination with

mepiquat chloride application at squaring as well as 600 ppm B in combination with

mepiquat chloride application at squaring during both years, and 600 ppm B in combination

with mepiquat chloride application at flowering during 2014, was statistically at par (Tables

4.87a, 4.88a). In case of effect of planting density, average boll weight of cotton was

decreased (6-11%) by planting the crop at higher density, across B and mepiquat chloride

treatments, as compared to lower planting density (Tables 4.87b, 4.88b).

The number of seeds per boll and seed index of cotton was significantly affected by

foliar applied B, foliar applied mepiquat chloride and planting density while the interactions

between B and mepiquat chloride, B and planting density, mepiquat chloride and planting

density and three way interaction among B, mepiquat chloride and planting density was

non-significant, during both years (Tables 4.89, 4.90). The seed cotton yield, lint yield and

cotton seed yield was significantly affected by B, mepiquat chloride, planting density,

interactions of B with mepiquat chloride, and B with planting density; while, the interactive

effect of mepiquat chloride with planting density and three way interaction of B, mepiquat

chloride and planting was non-significant for these traits, during both years (Tables 4.89,

4.90).

The number of seeds per boll and seed index of cotton was significantly affected by

foliar applied B, foliar applied mepiquat chloride and planting density while the interactions


density and three way interaction among B, mepiquat chloride and planting density was

non-significant, during both years. The seed cotton yield, lint yield and cotton seed yield

126

was significantly affected by B, mepiquat chloride, planting density, interactions B with

mepiquat chloride, and B with planting density; while, the interactive effect of mepiquat

chloride with planting density and three way interaction of B, mepiquat chloride and

planting was non-significant for these traits, during both years (Tables 4.89, 4.90).

The number of seeds per boll and seed index was increased by foliar application of

B as compared to control, during both years. It was noticed that application of 1200 ppm B

caused highest increase in number of seeds per boll and seed index, while, the effect of 600

ppm B was statistically at par during both years (Tables 4.91a, 4.92a, 4.93a, 4.94a).

Likewise application of mepiquat chloride increased the number of seeds per boll and seed

index during both years, as compared to control. The highest number of seeds per boll and

seed index was observed by application of mepiquat chloride at squaring stage,

nevertheless, the effect of mepiquat chloride application at flowering was statistically at

par, during both years (Tables 44.91a, 4.92a, 4.93a, 4.94a). Moreover, the number of seeds

per boll as well as seed index was decreased by increasing the planting density, during both

years (Tables 4.91b, 4.92b, 4.93b, 4.94b).

Seed cotton yield, lint yield and cotton seed yield was improved by the foliar

application of B, mepiquat chloride alone and in combination, as compared to control, and

it was noticed that application of B and mepiquat chloride in combination caused greater

improvement in yield as compared to their sole application, during both years. It was

noticed that application of 1200 ppm B in combination with mepiquat chloride at squaring

stage caused highest increase in seed cotton yield (30-35%) (Tables 4.95a, 4.96a), lint yield

(37-42%) (Tables 4.97a, 4.98a) as well as cotton seed yield (26-31%) (Tables 4.99a,

4.100a). Nevertheless, the effect of 1200 ppm B in combination with mepiquat chloride at

flowering produced similar results in improving yield, during both years (Tables 4.95a-

4.100a). Likewise, increasing the planting density resulted in an increase in seed cotton

yield (Tables 4.95b, 4.96b), lint yield (Tables 4.97b, 4.98b) and cotton seed yield (Tables

4.99b, 4.100b). Furthermore, application of B at both planting densities enhanced the seed

cotton yield (14-15 and 15-19% at lower and higher planting density, respectively), lint

yield (18-19 and 19-24% at lower and higher planting density, respectively) and cotton seed

yield (12-13 and 13-15% at lower and higher planting density, respectively), as compared

to their respective controls. Highest seed cotton yield, lint yield and cotton seed yield was

recorded by application of 1200 ppm B at higher planting density, as compared to control

during both years (Tables 4.95b-4.100b).

127


boron at various planting densities on yield and related attributes cotton (2014)



boron at various planting densities on yield and related attributes of cotton (2015)



Mean sum of squares

Seeds per

boll

Seed

index

Seed cotton

yield

Lint

yield

Cotton

seed yield

Replications 2 1.988 0.010 6254 1167 9945

Boron (B) 2 19.578** 0.931** 837046** 208898** 209860** Mepiquat chloride (M) 2 52.649** 0.688** 761459** 132990** 258997** Planting density (P) 1 8.059** 1.006** 1711940** 130776** 896402** B×M 4 0.480ns 0.041ns 67986** 12020* 23190* B×P 2 1.936ns 0.022ns 62785* 11343* 20772* M×P 2 0.244ns 0.010ns 4338ns 864ns 1348ns B×M×P 4 0.308ns 0.020ns 3302ns 230ns 1802ns Error 34 1.510 0.103 13483 3164 5953

Total 53


Mean sum of squares

Seeds per

boll

Seed

index

Seed cotton

yield

Lint

yield

Cotton

seed yield

Replications 2 0.324 0.210 40666 10470 9872 Boron (B) 2 13.676** 1.028** 590989** 130520** 166095** Mepiquat chloride (M) 2 52.412** 0.881** 538557** 90811** 187082**

Planting density (P) 1 8.153** 1.595** 623584** 57216** 303026** B×M 4 0.159ns 0.022ns 35325* 6275* 12479* B×P 2 1.458ns 0.011ns 47491* 9570* 14430* M×P 2 0.017ns 0.007ns 2614ns 259ns 1230ns B×M×P 4 0.344ns 0.036ns 1846ns 621ns 473ns Error 34 1.028 0.136 10177 2245 4212 Total 53

128


planting densities on number of seeds per boll of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 24.35 25.60 24.98 24.97 A

600 ppm B 25.48 26.08 25.62 25.72 B

1200 ppm B 25.64 27.57 27.90 27.04 B

Mean (MC) 25.15 B 26.42 A 26.17 A


25 cm 15 cm

Control 25.83 24.11 24.97 A

600 ppm B 26.90 24.55 25.72 B

1200 ppm B 27.97 26.11 27.04 B

Mean (P) 26.90 A 24.92 B


at squaring

MC application

at flowering

Mean (B)

Control 23.72 24.99 24.53 24.41 B

600 ppm B 24.95 26.31 24.97 25.41 A

1200 ppm B 25.12 26.48 26.84 26.15 A

Mean (MC) 24.60 B 25.93 A 25.44 A


25 cm 15 cm

Control 25.45 23.37 24.41 B

600 ppm B 26.45 24.37 25.41 A

1200 ppm B 27.02 25.27 26.15 A

Mean (P) 26.31 A 24.34 B

129


planting densities on seed index (g) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 7.01 7.37 7.38 7.25 B

600 ppm B 7.39 7.70 7.49 7.53 A

1200 ppm B 7.44 7.92 7.76 7.70 A

Mean (MC) 7.28 B 7.66 A 7.54 A


25 cm 15 cm

Control 7.39 7.12 7.25 B

600 ppm B 7.70 7.36 7.53 A

1200 ppm B 7.81 7.60 7.70 A

Mean (P) 7.63 A 7.36 B


at squaring

MC application

at flowering

Mean (B)

Control 6.97 7.35 7.21 7.18 B

600 ppm B 7.27 7.68 7.52 7.49 A

1200 ppm B 7.33 7.81 7.78 7.64 A

Mean (MC) 7.19 B 7.62 A 7.51 A


25 cm 15 cm

Control 7.35 7.00 7.18 B

600 ppm B 7.64 7.35 7.49 A

1200 ppm B 7.84 7.45 7.64 A

Mean (P) 7.61 A 7.26 B

130


planting densities on seed cotton yield (kg ha-1) (2014)








165.21.










143.53.


at squaring

MC application

at flowering

Mean (B)

Control 2435 e 2673 d 2624 de 2578 C

600 ppm B 2642 de 2990 bc 2810 cd 2814 B

1200 ppm B 2661 d 3296 a 3068 b 3008 A

Mean (MC) 2579 C 2986 A 2834 B


25 cm 15 cm

Control 2412 d 2743 c 2578 C

600 ppm B 2688 c 2941 b 2814 B

1200 ppm B 2766 c 3251 a 3008 A

Mean (P) 2622 B 2978 A


at squaring

MC application

at flowering

Mean (B)

Control 2278 f 2485 de 2413 def 2392 C

600 ppm B 2442 ef 2766 bc 2615 cd 2608 B

1200 ppm B 2473 de 2968 a 2814 ab 2752 A

Mean (MC) 2398 C 2740 A 2614 B


25 cm 15 cm

Control 2270 d 2514 bc 2392 C

600 ppm B 2557 c 2658 b 2608 B

1200 ppm B 2602 bc 2902 a 2752 A

Mean (P) 2476 B 2691 A

131


planting densities on lint yield (kg ha-1) of cotton (2014)








80.029.










67.409.


at squaring

MC application

at flowering

Mean (B)

Control 920 e 1012 de 1004 de 979 C

600 ppm B 1023 de 1178 bc 1102 cd 1101 B

1200 ppm B 1047 d 1307 a 1226 ab 1193 A

Mean (MC) 997 C 1165 A 1111 B


25 cm 15 cm

Control 935 d 1022 c 979 C

600 ppm B 1073 bc 1129 b 1101 B

1200 ppm B 1116 b 1270 a 1193 A

Mean (P) 1042 B 1140 A


at squaring

MC application

at flowering

Mean (B)

Control 854 e 936 cde 918 de 903 C

600 ppm B 938 cde 1069 b 1012 bc 1006 B

1200 ppm B 959 cd 1167 a 1090 ab 1072 A

Mean (MC) 917 C 1057 A 1007 B


25 cm 15 cm

Control 864 d 942 c 903 C

600 ppm B 999 bc 1013 b 1006 B

1200 ppm B 1020 b 1124 a 1072 A

Mean (P) 961 B 1026 A

132


planting densities on cotton seed yield (kg ha-1) (2014)








109.78.










92.330.


at squaring

MC application at

flowering

Mean (B)

Control 1515 d 1662 cd 1620 cd 1599 C 600 ppm B 1619 cd 1813 b 1707 bc 1713 B 1200 ppm B 1614 cd 1989 a 1842 ab 1815 A Mean (MC) 1583 C 1821 A 1723 B


25 cm 15 cm

Control 1477 d 1721 bc 1599 C

600 ppm B 1614 c 1812 b 1713 B

1200 ppm B 1649 c 1980 a 1815 A

Mean (P) 1580 B 1838 A


at squaring

MC application

at flowering

Mean (B)

Control 1424 d 1548 c 1495 cd 1489 C

600 ppm B 1504 cd 1698 ab 1603 bc 1601 B

1200 ppm B 1514 cd 1801 a 1725 ab 1680 A

Mean (MC) 1481 C 1682 A 1607 B


25 cm 15 cm

Control 1405 c 1572 b 1489 C

600 ppm B 1558 b 1645 b 1601 B

1200 ppm B 1582 b 1778 a 1680 A

Mean (P) 1515 B 1665 A

133

4.1.10. Discussion

The yield and related attributes of cotton were substantially improved by foliar

applied B and mepiquat chloride at both planting densities. It was observed that foliage

applied B and mepiquat chloride significantly interacted in improving the seed cotton yield,

lint yield and cotton seed yield. The increase in yield by B and mepiquat chloride is

attributed to increase in number of opened bolls and average boll weight. Furthermore,

number of seeds per boll and seed index was also improved by foliar application of B and

mepiquat chloride although B and mepiquat chloride did not interact in this regard. The

increase in number of bolls and boll weight might be the due to improved reproductive

growth and better assimilate partitioning. Besides, it is known that fibers are produced on

seed surface and thus the seed size and number of seeds are the function of yield (seed

cotton yield, lint yield as well as cotton seed yield) (Xiao-yu et al., 2016). In this study, the

number and size of cotton seed, and number of bolls was increased by B and mepiquat

chloride which seems to be the basic reason of yield increase.

It is known that B is involved in reproductive growth mainly in the pollen

development, pollen germination and pollen tube growth (Lee et al., 2009) thus affecting

the seed set and boll retention. Furthermore, B is involved in sugar synthesis, metabolism

and translocation thus affecting the source-sink relationship (Mengel and Kirkby, 2001;

Barker and Pilbeam, 2007). The improvement in boll size by B nutrition is attributed to

improved assimilate translocation during boll development. Number of seeds, seed weight

and number of bolls were further improved by application of mepiquat further leading to

improved yield. Mepiquat chloride causes a shift in balance from vegetative to reproductive

growth and alters the source-sink relationship indicating the bolls on treated plants as larger

sink for photosynthates (Gwathmey and Clement, 2010). In present study, the highest

number of bolls was notice by mepiquat chloride application at squaring stage but boll

weight was increased most by mepiquat chloride application at flowering stage. It seems to

be due to high boll load at plants receiving mepiquat chloride spray at squaring that might

have not met the full requirement of assimilates for boll development and vice versa for

mepiquat chloride treatment at flowering stage. Moreover, the number of seeds per boll

were also higher by application of mepiquat chloride at flowering stage which contributed

to higher boll weight.

Increasing the planting density resulted in a decrease in number of bolls and boll

weight per plant while substantially improved the number of bolls m-2 ultimately resulting

in improved seed cotton yield. Likewise, the lint yield and cotton seed yield was also

134

improved at higher planting density. However, the increase in lint yield was related to

higher seed cotton yield because the lint percentage was decreased in response to increase

in planting density. Furthermore, the decrease in lint percentage is attributed to decrease in

number of seeds and seed size at higher planting density. Decrease in number of bolls at

higher plant density is attributed to high LAI which causes mutual shading of plant canopy

leading to high boll shedding (Jost et al., 2006). Moreover, at very high LAI the biomass

partitioning to the reproductive structures is reduced consequently resulting in decreased

yield. However, according to Jost and Cothren (2001) greater yield reductions due to

reduced biomass partitioning for lint yield at high planting densities occur when the LAI is

>5. However, in present study the LAI remained <5 during both years due to which the

yield was increased as compared to lower planting density. Foliar applied B significantly

interacted with planting density. Boron application at both planting densities improved the

number of bolls per plant and boll weight which shows that B application ameliorated the

negative effects of higher planting density on boll retention. The enhanced boll retention

by B at higher planting density is attributed to its role in assimilate partitioning from source

to sink (Zhao and Oosterhuis, 2003). Therefore, enhanced assimilate translocation by B

application seems to be the reason of enhanced boll retention and boll weight, as compared

to control, at higher planting density. Furthermore, as discussed earlier that as the B is

involved in pollen tube development, pollen viability and seed set thus it enhanced the

number of seeds at higher planting density leading to higher fiber production and more

yield. On the other hand, although mepiquat chloride did not interact with planting density

but its effect was significant across the planting densities. This shows that mepiquat

chloride provided the yield benefit at both planting densities by reducing the excessive

vegetative growth, especially at higher planting density.

4.1.11. Fiber quality attributes

The fiber quality attributes were invariably affected by B, mepiquat chloride and

planting density during both years. It was observed that ginning out turn and micronaire

was significantly affected by B and planting density, while, the effect of mepiquat chloride,

interaction of B with mepiquat chloride, B with planting density, mepiquat chloride with

planting density, and three way interaction of B, mepiquat chloride and planting density

was non-significant, during both years (Tables 4.101 and 4.102). Fiber maturity was

significantly affected by B during 2014 and by planting density during both years, but, the

effect of mepiquat chloride and interactions of B with mepiquat chloride, B with planting

density, mepiquat chloride with planting density and three way interaction among B,

135

mepiquat chloride and planting density was non-significant during both years; moreover,

the effect of B was also non-significant during 2015 (Tables 4.101 and 4.102). Fiber length

was only affected by planting density during 2014; while, the effect of B, mepiquat

chloride, interactive effect between B and mepiquat chloride, B and planting density,

mepiquat chloride and planting density, and interaction among B, mepiquat chloride and

planting density was non-significant during both years (Tables 4.101 and 4.102).

Micronaire and fiber strength did not differ significantly by the influence of B, mepiquat

chloride, planting density, interactive effect of B and mepiquat chloride, B and planting

density, mepiquat chloride and planting density, and interaction among B, mepiquat

chloride and planting density during both years (Tables 4.101 and 4.102).

Boron application improved the ginning out turn, as compared to control, during

both years. Highest ginning out turn (39.7 and 38.9% during 2014 and 2015, respectively)

was recorded by foliar application of 1200 ppm B, while, the effect of 600 ppm B was

statistically similar during both years (Tables 103, 104). Ginning out turn was significantly

lower (38.2 and 38.1% during 2014 and 2015, respectively) at higher planting density, as

compared to lower planting density (Table 103, 104). Fiber length was significantly

affected by planting density during 2014 only and increasing the planting density decreased

the fiber length (Tables 105, 106). Micronaire was improved most at highest B application

rate (1200 ppm B) but 600 ppm B solution produced similar results, during both years

(Tables 107, 108). Planting density induced similar effect on micronaire as on other traits.

Higher planting density decreased the micronaire value, as compared to lower planting

density, during both years (Table 107, 108). Fiber maturity was improved by 1200 ppm B

and statistically similar results were recorded by application of 600 ppm B during 2014

only (Tables 4.113, 4.114). However, fiber maturity was decreased by increasing the

planting density, during both years (Tables 4.113, 4.114).

4.1.12. Discussion

The fiber quality attributes were invariably affected by B. Moreover, B application

improved some of the fiber quality traits i.e. ginning out turn, fiber length, fiber maturity

and micronaire while did not affect the fiber uniformity ratio and fiber strength. Ahmad et

al. (2009a) reported that foliar application of B improved the ginning out turn, staple length

and micronaire. Whereas, Ahmed et al. (2013) reported a non-significant improvement in

fiber quality attributes such as ginning out turn, fiber length, uniformity ratio, fiber strength

and fiber fineness by B application. Zhao and Oosterhuis (2002) also noticed a non-

significant effect of B on fiber quality attributes and opined that it is a genetically controlled

136

Table 4.101: Analysis of variance for influence of foliar applied mepiquat chloride

and boron at various planting densities on fiber quality of cotton (2014)



at various planting densities on fiber quality of cotton (2015)


Source of

variation DF

Mean sum of squares

Ginning

out

turn

Fiber

length

Micronaire Fiber

strength

Fiber

uniformity

ratio

Fiber

maturity

Replications 2 3.849 3.167 0.012 2.023 6.286 0.796 Boron (B) 2 13.258** 0.438ns 0.117* 0.234ns 0.126ns 11.241* Mepiquat

chloride (M)

2 1.271ns 0.111 ns 0.013ns 0.048ns 0.636ns 2.463ns

Planting

density (P)

1 29.526** 3.604* 0.156* 0.209ns 0.987ns 13.50*

B×M 4 0.133ns 0.071 ns 0.001ns 0.011ns 0.015ns 0.379ns B×P 2 0.091ns 0.046 ns 0.005ns 0.013ns 0.011ns 0.389ns

M×P 2 0.134ns 0.021ns 0.003ns 0.003ns 0.046ns 0.056ns B×M×P 4 0.067ns 0.111 ns 0.001ns 0.006ns 0.007ns 0.361ns Error 34 1.322 0.837 0.028 1.633 3.245 2.404 Total 53

Source of

variation DF

Mean sum of squares

Ginning

out

turn

Fiber

length

Micronaire Fiber

strength

Fiber

uniformity

ratio

Fiber

maturity

Replications 2 2.223 0.136 0.005 0.414 1.487 3.130 Boron (B) 2 6.577** 0.431ns 0.080* 0.205ns 0.576ns 4.519ns

Mepiquat

chloride (M)

2 0.526 0.122ns 0.005ns 0.127ns 0.304ns 1.685ns

Planting

density (P)

1 5.993* 0.690ns 0.135* 1.889ns 3.034ns 14.519**

B×M 4 0.387ns 0.006ns 1.852E-04ns 0.013ns 0.041ns 0.296ns B×P 2 0.244ns 0.031ns 5.556E-04ns 0.067ns 0.145ns 0.074ns M×P 2 0.007ns 0.087ns 0.00001ns 0.005ns 0.012ns 0.241ns

B×M×P 4 0.149ns 0.017 ns 5.556E-04ns 0.003ns 0.052ns 0.296ns Error 34 0.921 0.852 0.021 0.699 2.913 1.757 Total 53

137


planting densities on ginning out turn (%) of cotton (2014)




planting densities on ginning out turn (%) of cotton (2015)




planting densities on fiber length (mm) of cotton (2014)




planting densities on fiber length (mm) of cotton (2015)

P: Planting density, B: Boron.


25 cm 15 cm

Control 38.80 37.24 38.02 B

600 ppm B 39.92 38.36 39.14 A

1200 ppm B 40.37 39.05 39.71 A

Mean (P) 39.70 A 38.22 B


25 cm 15 cm

Control 38.07 37.46 37.76 B

600 ppm B 39.04 38.12 38.58 A

1200 ppm B 39.18 38.71 38.94 A

Mean (P) 38.76 A 38.10 B


25 cm 15 cm

Control 26.89 26.49 26.69

600 ppm B 27.15 26.58 26.86

1200 ppm B 27.29 26.71 27.00

Mean (P) 27.11 A 26.59 B


25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 26.63 26.77 26.73 26.53 26.57 26.60 26.64

600 ppm B 26.80 27.03 27.13 26.67 26.70 26.67 26.83

1200 ppm B 26.80 27.17 27.20 26.83 26.83 26.83 26.94

Mean (MC×P) 26.74 26.99 27.02 26.68 26.70 26.70

Mean (P) 26.92 26.69

138


planting densities on micronaire (µg inch-1) of cotton (2014)




densities on micronaire (µg inch-1

) of cotton (2015)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: mepiquat chloride, P: Planting density, B: Boron; HSD for P = 0.0794, HSD for B = 0.1175.


densities on fiber strength (g tex-1

) of cotton (2014)



densities on fiber strength (g tex-1

) of cotton (2015)



25 cm 15 cm

Control 4.48 4.41 4.44 B

600 ppm B 4.62 4.49 4.56 AB

1200 ppm B 4.66 4.54 4.60 A

Mean (P) 4.59 A 4.48 B


25 cm 15 cm

Control 4.41 4.32 4.37 B

600 ppm B 4.49 4.39 4.44 AB

1200 ppm B 4.56 4.44 4.50 A

Mean (P) 4.49 A 4.39 B


25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 23.50 23.70 23.63 23.40 23.50 23.53 23.54

600 ppm B 23.80 23.73 23.82 23.57 23.60 23.67 23.70

1200 ppm B 23.77 23.80 23.83 23.63 23.80 23.77 23.77

Mean (MC×P) 23.69 23.75 23.76 23.53 23.63 23.66

Mean (P) 23.73 23.61


25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 23.27 23.50 23.53 22.87 23.07 23.07 23.22

600 ppm B 23.43 23.53 23.60 22.97 23.13 23.10 23.29

1200 ppm B 23.47 23.57 23.60 23.30 23.30 23.33 23.43

Mean (MC×P) 23.39 23.53 23.58 23.04 23.17 23.17

Mean (P) 23.50 23.13

139


densities on fiber uniformity ratio (%) of cotton (2014)



planting densities on fiber uniformity ratio (%) of cotton (2015)



planting densities on fiber maturity (%) of cotton (2014)




planting densities on fiber maturity (%) of cotton (2015)




25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 52.00 52.37 52.40 51.90 52.17 52.03 52.14

600 ppm B 52.13 52.57 52.43 51.93 52.20 52.03 52.22

1200 ppm B 52.13 52.63 52.57 51.97 52.27 52.30 52.31

Mean (MC×P) 52.09 52.52 52.47 51.93 52.21 52.12

Mean (P) 52.36 52.09


25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application

at squaring

MC

application

at flowering

Mean

(B)

Control 51.27 51.57 51.70 50.97 51.40 51.23 51.36

600 ppm B 51.87 51.80 51.83 51.03 51.23 51.23 51.50

1200 ppm B 51.67 52.07 52.07 51.43 51.50 51.53 51.71

Mean (MC×P) 51.60 51.81 51.87 51.14 51.38 51.33

Mean (P) 51.76 51.29


25 cm 15 cm

Control 81.78 80.67 81.22 B

600 ppm B 83.11 81.89 82.50 A

1200 ppm B 83.00 82.33 82.67 A

Mean (P) 82.63 A 81.63 B


25 cm 15 cm

Control 81.89 81.00 81.44

600 ppm B 82.56 81.44 82.00

1200 ppm B 83.00 81.89 82.44

Mean (P) 82.48 A 81.44 B

140

character. However, Sabino et al. (1996) observed a significant effect of B on fiber length

and micronaire. However, mepiquat chloride did not impose a significant effect on fiber

quality. This might be due to the fact that mepiquat chloride have no direct effect on fiber

quality. Previous reports have shown an inconsistent effect of mepiquat chloride on fiber

quality. Çopur et al. (2010) reported that mepiquat chloride increased the lint percentage

but imposed a non-significant effect on fiber length, fineness, strength and uniformity.

Dodds et al. (2010) observed that mepiquat chloride decreased the lint percentage,

increased the fiber length while did not affect the micronaire, fiber strength and fiber

uniformity ratio of cotton. Similar to B, planting density also affected the fiber quality

attributes invariably. Awan et al. (2011) reported that some fiber traits were significantly

affected by planting density while most of the fiber quality attributes were non-significant.

It was perceived that fiber strength and ginning out turn was increased significantly at 30

and 20 cm row spacing, respectively; however, staple length, uniformity index and fiber

fineness were not affected significantly. Similarly, Jahedi et al. (2013) reported that fiber

length and fiber strength was decreased by increasing planting density showing an inverse

relationship.

4.1.13. Photosynthetic pigments

The photosynthetic pigments (chlorophyll a, b, total chlorophyll and carotenoids)

significantly differed by B, mepiquat chloride and planting density, and interactive effect

of B with mepiquat chloride. However, chlorophyll a, b and total chlorophyll did not affect

significantly by interactive effect of B with planting density, mepiquat chloride with

planting density and interaction among B, mepiquat chloride and planting density during

both years (Tables 4.115, 4.116). On the other hand, carotenoids were also significantly

affected by the interactive effect of mepiquat chloride with planting density during 2014

but did not affect during 2015. Moreover, the interaction between B and planting density,

and three way interaction among B, mepiquat chloride and planting density was non-

significant for carotenoids, during both years (Tables 4.115, 4.116). Boron application

significantly affected the chlorophyll a/b ratio during both years but mepiquat chloride and

planting density affected only during 2015. The chlorophyll a/b ratio did not differ

significantly by interactive effect of B and mepiquat chloride, B and planting density,

mepiquat chloride and planting density, and three way interaction of B, mepiquat chloride

and planting density during both years (Tables 4.115, 4.116).

Photosynthetic pigments were improved by foliar application of B and mepiquat

chloride as well as their combination, as compared to control. It was observed that the

141

highest increase in chlorophyll a (44-47%), chlorophyll b (53-57%), total chlorophyll (47-

49%) and carotenoids contents (36-46%) was caused by application of 1200 ppm B in

combination with mepiquat chloride at squaring stage, during both years. However, the

effect of 1200 ppm B in combination with mepiquat chloride application at flowering stage

was statistically similar on all the photosynthetic pigments, during 2015 (Tables 4.117a-

122a, 4.125a, 4.126a). In case of planting density the biosynthesis of chlorophyll a (6-15%),

chlorophyll b (5-7%) and total chlorophyll (6-13%) was decreased at higher planting

density, as compared to lower planting density during both years (4.117b-4.122b).

However, the carotenoids contents were improved by application of mepiquat chloride at

both planting densities (19 and 22% at lower and higher planting density, respectively), as

compared to the respective controls during 2014. The highest carotenoids content was

recorded by application of mepiquat chloride at squaring stage at lower planting density

and it was statistically at par with mepiquat chloride application at flowering stage at lower

planting density (Tables 4.125b, 4.126b). The chlorophyll a/b ratio was decreased by

application of B with highest decrease caused by application of 1200 ppm B solution,

during both years (Tables 4.123, 4.124a). Likewise, application of mepiquat chloride

caused a reduction in chlorophyll a/b ratio during 2015. The greatest decrease was caused

by application of mepiquat chloride at squaring while the effect of mepiquat chloride at

flowering was statistically similar (Table 4.124a). During 2015, the chlorophyll a/b ratio

was decreased by sowing the crop at higher planting density (Table 4.124b).

4.1.14. Discussion

Foliar applied B and mepiquat chloride significantly interacted in improving the

photosynthetic pigments in cotton leaves. A linear increase in chlorophyll a, b, total

chlorophyll and carotenoids contents was noticed by increase in B dosage. Furthermore,

mepiquat chloride application further enhanced the biosynthesis of photosynthetic

pigments. Boron deficiency exerts negative effects on hill reaction and net photosynthetic

rate, and increases the accumulation of starch and sugars in leaves which results in

deterioration of structure of chloroplast and reduces the biosynthesis of chlorophyll

contents (Sharma and Ramchandra, 1990; Han et al., 2008; Hao et al., 2012). However, B

application to plant in B deficient soil improves the leaf chlorophyll content (Rehman et

al., 2016). Seth and Arey (2014) reported that B nutrition of Vigna radiata improved the

biosynthesis of chlorophyll and carotenoids contents. The increase in chlorophyll content

has been reported by application of mepiquat chloride that may be the result of higher

specific leaf weight or it may be due to enhanced biosynthesis of chlorophyll (Reddy et al.,

142


at various planting densities on photosynthetic pigments of cotton (2014)



at various planting densities on photosynthetic pigments of cotton (2015)


Source of variation DF Mean sum of squares

Chl a Chl b Total Chl Chl a/b Carotenoids

Replications 2 0.00004 0.00009 0.00007 0.0103 0.00007 Boron (B) 2 0.02591** 0.00608** 0.05727** 0.0446** 0.00215** Mepiquat chloride (M) 2 0.07194** 0.01261** 0.13862** 0.0066ns 0.00701** Planting density (P) 1 0.01534** 0.00107** 0.02535** 0.0258ns 0.00445** B×M 4 0.00233** 0.00046** 0.00447** 0.0018ns 0.00020**

B×P 2 0.00052ns 0.00007ns 0.00091ns 0.0014ns 0.00001ns M×P 2 0.00039ns 0.00004ns 0.00074ns 0.0020ns 0.00025** B×M×P 4 0.00079ns 0.00004ns 0.00101ns 0.0032ns 0.00004ns Error 34 0.00042 0.00006 0.00055 0.0081 0.00004 Total 53


Mean sum of squares

Chl a Chl b Total

Chl

Chl a/b Carotenoids

Replications 2 0.00048 0.00004 0.00078 0.004 0.00003

Boron (B) 2 0.06701** 0.01102** 0.13472** 0.073** 0.00518** Mepiquat chloride (M) 2 0.10041* 0.01362** 0.18445** 0.040** 0.00672** Planting density (P) 1 0.16445** 0.00445** 0.21914** 1.042** 0.00602** B×M 4 0.00440** 0.00049** 0.00782** 0.004 0.00056** B×P 2 0.00045ns 0.00010ns 0.00056ns 0.011ns 0.00017ns M×P 2 0.00046ns 0.00005ns 0.00083ns 0.003ns 0.00001ns B×M×P 4 0.00119ns 0.00016ns 0.00214ns 0.008ns 0.00006ns Error 34 0.00061 0.00007 0.00095 0.006 0.00010

Total 53

143


planting densities on chlorophyll a content (mg g-1) of cotton (2014)



= 0.0390.















at squaring

MC application

at flowering

Mean (B)

Control 0.44 g 0.52 de 0.53 cd 0.50 C

600 ppm B 0.47 fg 0.59 b 0.57 bc 0.54 B

1200 ppm B 0.49 ef 0.64 a 0.59 b 0.57 A

Mean (MC) 0.47 B 0.58 A 0.57 A


25 cm 15 cm

Control 0.51 0.48 0.50 C

600 ppm B 0.56 0.52 0.54 B

1200 ppm B 0.58 0.56 0.57 A

Mean (P) 0.55 A 0.52 B


at squaring

MC application

at flowering

Mean (B)

Control 0.54 e 0.62 d 0.62 d 0.59 C

600 ppm B 0.59 d 0.73 bc 0.69 c 0.67 B 1200 ppm B 0.60 d 0.79 a 0.76 ab 0.71 A Mean (MC) 0.58 C 0.71 A 0.69 B


25 cm 15 cm

Control 0.64 0.54 0.59 C 600 ppm B 0.73 0.61 0.67 B 1200 ppm B 0.77 0.66 0.71 A

Mean (P) 0.71 A 0.60 B

144


planting densities on chlorophyll b content (mg g-1) of cotton (2014)


















at squaring

MC application

at flowering

Mean (B)

Control 0.16 f 0.20 cd 0.21 c 0.19 C

600 ppm B 0.18 e 0.23 b 0.22 b 0.21 B

1200 ppm B 0.19 de 0.25 a 0.23 b 0.22 A

Mean (MC) 0.18 C 0.23 A 0.22 B


25 cm 15 cm

Control 0.19 0.18 0.19 C

600 ppm B 0.21 0.20 0.21 B

1200 ppm B 0.23 0.22 0.22 A

Mean (P) 0.21 A 0.20 B


at squaring

MC application

at flowering

Mean (B)

Control 0.17 e 0.21 d 0.20 d 0.19 C

600 ppm B 0.19 d 0.25 bc 0.23 c 0.22 B

1200 ppm B 0.20 d 0.27 a 0.26 ab 0.24 A

Mean (MC) 0.19 C 0.24 A 0.23 B


25 cm 15 cm

Control 0.20 0.19 0.19 C

600 ppm B 0.23 0.22 0.22 B

1200 ppm B 0.25 0.23 0.24 A

Mean (P) 0.23 A 0.21 B

145


planting densities on total chlorophyll content (mg g-1) of cotton (2014)



= 0.0447.















at squaring

MC application

at flowering

Mean (B)

Control 0.61 f 0.72 cd 0.73 c 0.68 C

600 ppm B 0.65 e 0.81 b 0.79 b 0.75 B

1200 ppm B 0.67 de 0.89 a 0.82 b 0.80 A

Mean (MC) 0.64 C 0.81 A 0.78 B


25 cm 15 cm

Control 0.71 0.66 0.68 C

600 ppm B 0.78 0.72 0.75 B

1200 ppm B 0.81 0.78 0.80 A

Mean (P) 0.76 A 0.72 B


at squaring

MC application

at flowering

Mean (B)

Control 0.71 e 0.83 d 0.82 d 0.79 C

600 ppm B 0.78 d 0.98 bc 0.92 c 0.89 B

1200 ppm B 0.80 d 1.06 a 1.01 ab 0.96 A

Mean (MC) 0.76 C 0.95 A 0.92 B


25 cm 15 cm

Control 0.84 0.73 0.79 C

600 ppm B 0.96 0.83 0.89 B

1200 ppm B 1.02 0.89 0.96 A

Mean (P) 0.94 A 0.82 B

146


planting densities on chlorophyll a/b ratio of cotton (2014)






density, B: Boron; HSD for MC = 0.0653, HSD for B = 0.0653.




chloride, B: Boron; HSD for P = 0.0441, HSD for B = 0.0653.


planting densities on carotenoids content (mg g-1) of cotton (2014)





25 cm 15 cm

Control 2.69 2.63 2.66 A

600 ppm B 2.64 2.58 2.61 AB

1200 ppm B 2.57 2.55 2.56 B

Mean (P) 2.63 2.59


at squaring

MC application

at flowering

Mean (B)

Control 3.12 3.00 3.10 3.07 A

600 ppm B 3.05 2.97 2.99 3.00 B

1200 ppm B 3.00 2.91 2.93 2.95 B

Mean (MC) 3.06 A 2.96 B 3.00 AB


25 cm 15 cm

Control 3.20 2.94 3.07 A

600 ppm B 3.17 2.84 3.00 B

1200 ppm B 3.07 2.83 2.95 B

Mean (P) 3.15 A 2.87 B


at squaring

MC application

at flowering

Mean (B)

Control 0.15 e 0.17 c 0.17 c 0.16 C

600 ppm B 0.15 e 0.19 ab 0.18 b 0.18 B

1200 ppm B 0.16 d 0.20 a 0.20 a 0.19 A

Mean (MC) 0.15 B 0.19 A 0.19 A

147




density, B: Boron; HSD for P = 0.0035, HSD for B = 0.0051, HSD for MC×P interaction

= 0.0089.










25 cm 15 cm

Control 0.16 c 0.15 d 0.16 C

MC application at squaring 0.20 a 0.18 b 0.18 B

MC application at flowering 0.19 a 0.18 b 0.19 A

Mean (P) 0.19 A 0.17 B


at squaring

MC application

at flowering

Mean (B)

Control 0.16 e 0.18 cd 0.18 cd 0.17 C

600 ppm B 0.17 de 0.20 bc 0.20 bc 0.19 B

1200 ppm B 0.18 cd 0.23 a 0.22 ab 0.21 A

Mean (MC) 0.17 B 0.21 A 0.20 A


25 cm 15 cm

Control 0.19 0.16 0.17 C

600 ppm B 0.20 0.18 0.19 B

1200 ppm B 0.22 0.20 0.21 A

Mean (P) 0.20 A 0.18 B

148

1996; Rosolem et al., 2013). Present study results showed that higher chlorophyll a, b, total

chlorophyll and carotenoid contents were noticed by mepiquat chloride application at

squaring than flowering stage which might be due to greater reduction in leaf area by

mepiquat chloride application at squaring stage or due to higher specific leaf weight.

However, in this study higher planting density significantly decreased the leaf chlorophyll

and carotenoids contents as compared to lower planting density. Similar results were

reported by Ren et al. (2017) that increasing the planting density of maize from 30,000 to

135,000 plants ha-1 declined the chlorophyll a, b, total chlorophyll and carotenoids contents

along with decrease in net photosynthesis and number of chloroplasts, damaged membrane

structure of mesophyll cells and number of grana.

4.1.15. Tissue nutrient contents

4.1.15.1. Macronutrients

The macronutrients content (nitrogen, phosphorus and potassium) in leaf and seed

tissues was significantly affected by application of B, mepiquat chloride and planting

density. However, the interactive effects of B and mepiquat chloride, B and planting

density, mepiquat chloride and planting density as well as B, mepiquat chloride and

planting density was non-significant, during both years (Tables 4.127, 4.128).

Foliar applied B and mepiquat chloride improved the contents of macronutrients in

leaf and seed tissues of cotton at both planting densities, as compared to control during both

years. Highest increase in N contents in leaf (10%) and cotton seed tissues (4-5%) was

noticed by application of 1200 ppm B. However, application of 600 ppm B produced

statistically similar results for cotton seed N contents during both years (Tables 4.129a,

4.130a, 4.131a, 4.132a). Likewise, mepiquat chloride application at squaring stage caused

the greatest improvement in N contents in leaf (12%) and cotton seed tissues (4%), as

compared to control. However, the effect of mepiquat chloride at flowering was statistically

similar for leaf N during 2014 and seed N during both years (Tables 4.129a, 4.130a, 4.131a,

4.132a). However, increasing the planting density decrease the N contents in leaf (4-9%)

and seed tissues (2%), as compared to lower planting density (Tables 4.129b, 4.130b,

4.131b, 4.132b).

Similarly, leaf P content (12-16%) and cotton seed P content (10-12%) were

enhanced by application of 1200 ppm B, as compared to control. However, application of

600 ppm B produced statistically similar results for cotton seed P content during 2015

(Tables 4.133a, 4.134a, 4.135a, 4.136a). Mepiquat chloride application at squaring stage

caused similar increase in P contents in leaf (7-10%) and seed tissues (8-12%), as compared

149


and boron at various planting densities on contents of macronutrients in leaves and

seed tissues of cotton (2014)



and boron at various planting densities on contents of macronutrients in leaves and

seed tissues of cotton (2015)



Mean sum of squares

Nitrogen Phosphorus Potassium

Leaf Seed Leaf Seed Leaf Seed

Replications 2 75.609 0.263 0.013 0.019 8.150 17.850

Boron (B) 2 17.841** 9.389** 0.200** 0.589** 23.383** 21.438**

Mepiquat chloride (M) 2 23.739** 7.125** 0.048** 0.406** 26.942** 22.184**

Planting density (P) 1 10.543** 6.970* 0.286** 0.552** 39.424** 55.025**

B×M 4 1.034ns 0.203ns 0.005ns 0.009ns 0.675ns 0.504ns

B×P 2 0.052ns 0.116ns 0.0026ns 0.013ns 0.226ns 1.069ns

M×P 2 1.964ns 0.005ns 0.003ns 0.005ns 1.241ns 0.160ns


Error 34 0.843 1.267 0.007 0.017 1.225 1.325

Total 53


Mean sum of squares



Replications 2 0.792 1.797 0.022 0.021 0.384 0.239

Boron (B) 2 23.018** 8.836** 0.115** 0.841** 16.079** 14.799**

Mepiquat chloride (M) 2 31.596** 8.112** 0.081** 0.772** 18.815** 16.378**

Planting density (P) 1 63.614** 6.476* 0.698** 1.319** 21.711** 33.418**

B×M 4 0.793ns 0.046ns 0.006ns 0.052ns 0.121ns 0.143ns

B×P 2 0.315ns 0.034ns 0.001ns 0.004ns 0.026ns 0.130ns

M×P 2 0.020ns 0.021ns 0.001ns 0.008ns 0.018ns 0.041ns


Error 34 1.218 1.334 0.006 0.029 1.039 0.744

Total 53

150


planting densities on leaf nitrogen content (mg g -1 DW) of cotton (2014)




planting densities on leaf nitrogen content (mg g-1 DW) of cotton (2014)












at squaring

MC application

at flowering

Mean (B)

Control 18.63 20.45 20.04 19.71 C

600 ppm B 19.66 21.49 20.82 20.66 B

1200 ppm B 20.10 23.28 21.71 21.70 A

Mean (MC) 19.46 C 21.74 A 20.85 B


25 cm 15 cm

Control 20.20 19.21 19.71 C

600 ppm B 21.09 20.22 20.66 B

1200 ppm B 22.09 21.31 21.70 A

Mean (P) 21.13 A 20.24 B


at squaring

MC application

at flowering

Mean (B)

Control 20.79 22.79 22.15 21.91 C

600 ppm B 21.72 24.10 23.84 23.22 B

1200 ppm B 22.32 25.58 24.57 24.16 A

Mean (MC) 21.61 B 24.16 A 23.52 A


25 cm 15 cm

Control 23.05 20.76 21.91 C

600 ppm B 24.40 22.04 23.22 B

1200 ppm B 25.09 23.22 24.16 A

Mean (P) 24.18 A 22.01 B

151


planting densities on seed nitrogen content (mg g-1 DW) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 31.09 32.58 31.75 31.81 B

600 ppm B 32.01 32.97 32.50 32.49 AB

1200 ppm B 32.49 33.80 33.47 33.25 A

Mean (MC) 31.86 B 33.12 A 32.58 AB


25 cm 15 cm

Control 32.15 31.47 31.81 B

600 ppm B 32.79 32.20 32.49 AB

1200 ppm B 33.70 32.80 33.25 A

Mean (P) 32.88 A 32.16 B


at squaring

MC application

at flowering

Mean (B)

Control 30.41 31.69 31.02 31.04 B

600 ppm B 31.26 32.56 31.87 31.90 AB

1200 ppm B 31.64 33.08 32.56 32.43 A

Mean (MC) 31.10 B 32.45 A 31.82 AB


25 cm 15 cm

Control 31.43 30.65 31.04 B

600 ppm B 32.24 31.55 31.90 AB

1200 ppm B 32.73 32.12 32.43 A

Mean (P) 32.13 A 31.44 B

152


planting densities on leaf phosphorus content (mg g-1 DW) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 1.27 1.39 1.36 1.34 C

600 ppm B 1.41 1.46 1.42 1.43 B

1200 ppm B 1.47 1.61 1.58 1.55 A

Mean (MC) 1.38 B 1.48 A 1.45 A


25 cm 15 cm

Control 1.40 1.28 1.34 C

600 ppm B 1.51 1.34 1.43 B

1200 ppm B 1.62 1.48 1.55 A

Mean (P) 1.51 A 1.37 B


at squaring

MC application

at flowering

Mean (B)

Control 1.22 1.37 1.27 1.29 C

600 ppm B 1.32 1.42 1.37 1.37 B

1200 ppm B 1.34 1.50 1.49 1.44 A

Mean (MC) 1.29 B 1.43 A 1.38 A


25 cm 15 cm

Control 1.39 1.18 1.29 C

600 ppm B 1.48 1.25 1.37 B

1200 ppm B 1.56 1.33 1.44 A

Mean (P) 1.48 A 1.25 B

153


planting densities on seed phosphorus content (mg g-1 DW) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 3.36 3.70 3.64 3.57 C

600 ppm B 3.66 3.89 3.80 3.79 B

1200 ppm B 3.76 4.05 3.98 3.93 A

Mean (MC) 3.59 C 3.88 A 3.81 A


25 cm 15 cm

Control 3.69 3.45 3.57 C

600 ppm B 3.86 3.72 3.79 B

1200 ppm B 4.04 3.81 3.93 A

Mean (P) 3.86 A 3.66 B


at squaring

MC application

at flowering

Mean (B)

Control 3.18 3.37 3.38 3.31 B

600 ppm B 3.39 3.84 3.69 3.64 A

1200 ppm B 3.39 3.93 3.83 3.72 A

Mean (MC) 3.32 B 3.71 A 3.63 A


25 cm 15 cm

Control 3.47 3.15 3.31 B

600 ppm B 3.78 3.50 3.64 A

1200 ppm B 3.89 3.54 3.72 A

Mean (P) 3.71 A 3.40 B

154


planting densities on leaf potassium content (mg g-1 DW) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 19.56 21.75 20.60 20.64 C

600 ppm B 20.84 22.89 21.99 21.91 B

1200 ppm B 21.53 24.61 22.58 22.91 A

Mean (MC) 20.64 C 23.09 A 21.73 B


25 cm 15 cm

Control 21.43 19.85 20.64 C

600 ppm B 22.89 20.93 21.91 B

1200 ppm B 23.70 22.12 22.91 A

Mean (P) 22.67 A 20.97 B


at squaring

MC application

at flowering

Mean (B)

Control 19.36 21.45 20.75 20.52 C

600 ppm B 20.61 22.45 21.52 21.53 B

1200 ppm B 21.29 23.48 22.45 22.41 A

Mean (MC) 20.42 C 22.46 A 21.57 B


25 cm 15 cm

Control 21.15 19.89 20.52 C

600 ppm B 22.20 20.85 21.53 B

1200 ppm B 23.01 21.81 22.41 A

Mean (P) 22.12 A 20.85 B

155


planting densities on seed potassium content (mg g-1 DW) of cotton (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 17.04 19.16 18.52 18.24 C

600 ppm B 18.36 20.04 19.31 19.24 B

1200 ppm B 18.91 21.68 20.67 20.42 A

Mean (MC) 18.10 B 20.29 A 19.50 A

Treatments 53333 plants ha-1

88888 plants ha-1

Mean (B)

25 cm 15 cm

Control 19.51 16.97 18.24 C

600 ppm B 20.21 18.26 19.24 B

1200 ppm B 21.20 19.64 20.42 A

Mean (P) 20.31 A 18.29 B


at squaring

MC application

at flowering

Mean (B)

Control 16.37 18.01 17.39 17.26 C

600 ppm B 17.38 19.23 18.35 18.32 B

1200 ppm B 17.91 20.13 19.14 19.06 A

Mean (MC) 17.22 B 19.12 A 18.29 A


25 cm 15 cm

Control 18.10 16.41 17.26 C

600 ppm B 19.15 17.49 18.32 B

1200 ppm B 19.75 18.37 19.06 A

Mean (P) 19.00 A 17.43 B

156

to control. However, the effect of mepiquat chloride at flowering was statistically similar,

during both years (Tables 4.133a, 4.134a, 4.135a, 4.136a). However, similar to N,

increasing the planting density decreased the P contents in leaf (10-15%) and seed tissues

(5-8%), during both years (Tables 4.133b, 4.134b, 4.135b, 4.136b).

Highest increase in K contents in leaf (9-11%) and seed tissues (10-12%) were noticed by

application of 1200 ppm B solution, as compared to control (Tables 4.137a, 4.138a, 4.139a,

4.140a). Similarly, mepiquat chloride application at squaring stage caused maximum

increase in K contents in leaf (10-12%) and seed tissues (11-12%), as compared to control.

However, the effect of mepiquat chloride at flowering was statistically similar for seed K

contents during both years (Tables 4.137a, 4.138a, 4.139a, 4.140a). On the other hand,

sowing the crop at higher planting density caused a reduction in K contents in both leaf (6-

8%) and seed tissues (6-10%) of cotton during both years (Tables 4.202-4.225).

4.1.15.2. Micronutrients

Leaf and cotton seed B, Zn, Mn, and cotton seed Fe contents in leaves and cotton

seed were significantly affected by boron, mepiquat chloride, planting density. Leaf Fe

content was improved by boron and planting density during both years while the effect of

mepiquat chloride was significant during 2015 while non-significant during 2014.

However, leaf and cotton seed B content were also significantly affected by interactive

effects of B with mepiquat chloride and B with planting density during both years while by

interaction between mepiquat chloride with planting density during 2015 only but the three

way interaction among B, mepiquat chloride and planting density was non-significant,

during both years (Tables 4.141, 4.142). On the other hand, Zn, Mn and Fe contents in leaf

and cotton seed did not differ significantly by interactive effect between B and mepiquat

chloride, B and planting density, mepiquat chloride and planting density and three way

interaction among B, mepiquat chloride and planting density, during both years (Tables

4.141, 4.142).

The leaf and cotton seed B contents were substantially improved by application of

B and mepiquat chloride alone as well as in combination, as compared to control. It was

observed that highest increase in leaf B contents (59-63%) and cotton seed B contents (59-

60%) was occurred when the crop was treated with 1200 ppm B in combination with

mepiquat chloride application at squaring stage, during both years (Tables 4.143a, 4.144a,

4.145a, 4.146a). Conversely, sowing the crop at higher planting caused a reduction in leaf

and cotton seed B contents as compared to lower planting density, during both years.

However, application of B at both planting densities improved the leaf B content (29-38

157

and 40-42% at lower and higher planting density, respectively) and seed B content (28-35

and 36-38% at lower and higher planting density, respectively) with maximum contents

occurring by application of 1200 ppm B at lower planting density. Whereas, 600 ppm B at

lower planting density produced similar results for cotton seed B contents during 2015

(Tables 4.143b, 4.144b, 4.145b, 4.146b). Similarly, application of mepiquat chloride at

both planting densities improved the leaf (14 and 9% at lower and higher planting density,

respectively) and cotton seed B contents (15 and 11% at lower and higher planting density,

respectively), as compared to control during 2015. Maximum B contents in leaf and cotton

seed was recorded by application of mepiquat chloride at squaring stage at lower plating

density, as compared to their respective controls, while the effect of mepiquat chloride at

flowering stage at lower plating density was statistically similar (Tables 4.144c, 4.146c).

Application of B improved the Zn contents in leaves (9-13%) and cotton seed (10-

11%), as compared to control during both years. The greatest increase in Zn contents was

resulted by application of 1200 ppm B solution during both years (Tables 4.147a, 4.148a,

4.149a, 4.150a). Similarly, application of mepiquat chloride improved the leaf and seed Zn

contents, during both years. It was noticed that application of mepiquat chloride at squaring

stage caused greatest increase in leaf (7-9%) and seed Zn contents (8-9%), as compared to

control. Furthermore, application of mepiquat chloride at flowering stage produced similar

results for leaf Zn during both years, while for seed Zn during 2014 (Tables 4.147a, 4.148a,

4.149a, 4.150a). However, higher planting density caused a reduction in Zn contents in both

leaves (9-11%) and seed (5-7%), as compared to lower planting density, during both years

(Tables 4.147b, 4.148b, 4.149b, 4.150b).

Leaf and seed Mn contents were decreased in response to foliar applied B, during

both years. Application of 1200 ppm B declined the Mn contents most in leaves (11-13%)

and seed (10-11%), during both years (Tables 4.151a, 4.152a, 4.53a, 4.154a). Similarly,

mepiquat chloride spray decreased the leaf and seed Mn contents, during both years. It was

noticed that application of mepiquat chloride at squaring stage caused maximum decrease

in Mn contents in leaf (6%) and cotton seed (5-6%), as compared to control. Furthermore,

application of mepiquat chloride at flowering stage produced similar results (Tables 4.151a,

4.152a, 4.53a, 4.154a). Furthermore, leaf Mn content (6-9%) and seed Mn content (7-9%)

were further decreased in response to increase in planting density, during both years (Tables

4.151b, 4.152b, 4.53b, 4.154b). Foliar applied B improved the leaf Fe content (9-14%) and

seed Fe content (11-14%) with maximum increase occurring at 1200 ppm B, during both

years (Tables 4.155, 4.156a, 4.157a, 4.158a). Application of mepiquat chloride improved

158

Table 4.141: Analysis of variance for influence of foliar applied mepiquat chloride and boron at various planting densities on contents of



Table 4.142: Analysis of variance for influence of foliar applied mepiquat chloride and boron at various planting densities on contents of




Mean sum of squares

Boron Zinc Manganese Iron

Leaf Seed Leaf Seed Leaf Seed Leaf Seed

Replications 2 0.384 0.23 1.284 15.5084 11.017 0.7427 25.18 3.46

Boron (B) 2 640.227** 648.99** 89.641** 99.2148** 194.171** 21.0170** 2283.46** 2654.39**

Mepiquat chloride (M) 2 174.517** 241.71** 48.010** 68.6778** 46.813** 6.4502* 110.47 181.36*

Planting density (P) 1 152.679** 1250.89** 153.925** 74.0611** 244.524** 44.0285** 474.25* 738.96**

B×M 4 8.780** 6.06* 2.063ns 3.1305ns 8.801ns 0.1522ns 30.84ns 16.16ns

B×P 2 7.312* 8.72* 1.511ns 0.9814ns 0.155ns 0.3179ns 1.83ns 4.75ns



Error 34 2.135 2.08 2.911 3.2044 6.079 1.6762 64.53 50.16

Total 53


Mean sum of squares



Replications 2 6.625 0.198 0.028 1.012 11.460 0.952 187.361 335.492

Boron (B) 2 625.232** 599.689** 42.034** 75.701** 138.251** 26.668** 1018.180** 1426.913**

Mepiquat chloride (M) 2 143.403** 173.879** 23.515** 52.117** 37.915** 5.121* 200.742* 353.354**

Planting density (P) 1 542.831** 967.401** 240.245** 123.216** 133.010** 29.113** 680.534** 500.931**

B×M 4 7.084** 9.922** 1.680ns 0.522ns 4.856ns 0.069ns 30.291ns 63.680ns

B×P 2 5.532* 6.881* 2.135ns 1.859ns 2.890ns 0.239ns 6.530ns 29.281ns

M×P 2 6.018* 7.004* 0.071ns 1.137ns 5.161ns 0.399ns 25.701ns 18.910ns


Error 34 1.592 1.870 2.752 4.183 5.134 1.342 38.711 43.801

Total 53

159

Table 4.143a: Influence of foliar applied mepiquat chloride and boron at various planting

densities on leaf boron content (µg g-1 DW) of cotton (2014)


chloride, B: Boron; HSD for MC = 1.1938, HSD for B = 1.1938, HSD for MC×P interaction =

2.7914.

Table 4.143b: Influence of foliar applied mepiquat chloride and boron at various planting


Values sharing the same case letters do not differ significantly at p ≤ 0.05; P: Planting density,

B: Boron; HSD for P = 0.8072, HSD for B = 1.1938, HSD for B×P interaction = 2.0790.





= 2.4103.




chloride, B: Boron; HSD for P = 0.6970, HSD for B = 1.0308, HSD for P×B interaction =

1.7951.


at squaring

MC application

at flowering

Mean (B)

Control 31.50 g 35.96 f 35.34 f 34.27 C

600 ppm B 39.60 e 44.80 bc 42.46 cd 42.29 B

1200 ppm B 41.30 de 50.03 a 46.42 b 45.92 A

Mean (MC) 37.47 C 43.60 A 41.41 B


25 cm 15 cm

Control 36.68 d 31.86 e 34.27 C

600 ppm B 43.69 b 40.89 c 42.29 B

1200 ppm B 47.15 a 44.69 b 45.92 A

Mean (P) 42.50 A 39.14 B


at squaring

MC application

at flowering

Mean (B)

Control 27.32 f 30.71 e 29.82 e 29.29 C

600 ppm B 33.66 d 39.23 bc 38.16 c 37.02 B

1200 ppm B 36.85 c 44.40 a 41.33 b 40.86 A

Mean (MC) 32.61 C 38.11 A 36.44 B


25 cm 15 cm

Control 31.95 d 26.62 e 29.29 C

600 ppm B 40.78 b 33.26 d 37.02 B

1200 ppm B 43.94 a 37.77 c 40.86 A

Mean (P) 38.89 A 32.55 B

160

Table 4.144c: Influence of foliar applied mepiquat chloride and boron at various planting


Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for P = 0.6970, HSD for MC = 1.0308, HSD for P×MC interaction = 1.7951.


densities on seed boron content (µg g-1 DW) of cotton (2014)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride,

B: Boron; HSD for MC = 1.1797, HSD for B = 1.1797, HSD for MC×P interaction = 2.7583.



Values sharing the same case letters do not differ s ignif icantly at p ≤ 0. 05; P: Planting dens ity, B: Bo ron; HSD for P = 0.7977, HSD fo r B = 1.1797 , HSD fo r B×P i nteraction = 2.0544.

Values sharing the same case letters do not differ significantly at p ≤ 0.05; P: Planting density, B: Boron; HSD for P = 0.7977, HSD for B = 1.1797, HSD for B×P interaction = 2.0544.





= 2.6123.

Treatments Plant spacing Mean (MC)

25 cm 15 cm

Control 35.18 b 30.04 d 32.61 C

MC application at squaring 41.34 a 34.89 b 38.11 A

MC application at flowering 40.16 a 32.72 c 36.44 B

Mean (P) 38.89 A 32.55 B


at squaring

MC application

at flowering

Mean (B)

Control 32.91 h 39.43 fg 37.85 g 36.73 C

600 ppm B 42.16 ef 48.05 bc 45.33 cd 45.18 B

1200 ppm B 43.30 de 52.59 a 49.08 b 48.32 A

Mean (MC) 39.46 C 46.69 A 44.09 B


25 cm 15 cm

Control 41.14 c 32.32 d 36.73 C

600 ppm B 50.81 a 39.56 c 45.18 B

1200 ppm B 52.74 a 43.90 b 48.32 A

Mean (P) 48.23 A 38.59 B


at squaring

MC application

at flowering

Mean (B)

Control 28.85 f 32.32 e 31.30 ef 30.82 C

600 ppm B 35.04 d 41.22 bc 40.13 c 38.79 B

1200 ppm B 37.38 d 45.75 a 42.99 b 42.04 A

Mean (MC) 33.76 C 39.76 A 38.14 B

161




chloride, B: Boron; HSD for P = 0.7554, HSD for B = 1.1173, HSD for P×B interaction =

1.9456.

Table 4.146c: Influence of foliar applied mepiquat chloride and boron at various planting



chloride, B: Boron; HSD for P = 0.7554, HSD for MC = 1.1173, HSD for P×MC interaction

= 1.9456.


densities on leaf zinc content (µg g-1 DW) of cotton (2014)






B: Boron; HSD for P = 0.9426, HSD for B = 1.3940.


25 cm 15 cm

Control 34.39 d 27.25 e 30.82 C

600 ppm B 43.59 b 34.00 d 38.79 B

1200 ppm B 46.38 a 37.70 c 42.04 A

Mean (P) 41.45 A 32.99 B

Treatments Plant spacing Mean (MC)

25 cm 15 cm

Control 37.29 b 30.22 e 33.76 C

MC application at squaring 44.18 a 35.35 c 39.76 A

MC application at flowering 42.89 a 33.40 d 38.14 B

Mean (P) 41.45 A 32.99 B


at squaring

MC application

at flowering

Mean (B)

Control 33.34 36.15 35.08 34.85 C

600 ppm B 35.46 38.21 37.28 36.98 B

1200 ppm B 36.80 40.54 40.61 39.32 A

Mean (MC) 35.20 B 38.30 A 37.66 A


25 cm 15 cm

Control 36.24 33.47 34.85 C

600 ppm B 38.69 35.27 36.98 B

1200 ppm B 41.28 37.35 39.32 A

Mean (P) 38.74 A 35.36 B

162










densities on seed zinc content (µg g-1 DW) of cotton (2014)








at squaring

MC application

at flowering

Mean (B)

Control 31.89 35.18 33.25 33.44 C

600 ppm B 34.10 35.82 35.16 35.03 B

1200 ppm B 35.36 37.16 36.97 36.50 A

Mean (MC) 33.78 B 36.06 A 35.13 AB


25 cm 15 cm

Control 35.47 31.42 33.44 C

600 ppm B 36.84 33.21 35.03 B

1200 ppm B 38.99 34.01 36.50 A

Mean (P) 37.10 A 32.88 B


at squaring

MC application

at flowering

Mean (B)

Control 39.41 43.10 41.49 41.33 C

600 ppm B 41.81 44.62 43.76 43.40 B

1200 ppm B 42.98 47.76 47.31 46.02 A

Mean (MC) 41.40 B 45.16 A 44.18 A


25 cm 15 cm

Control 42.34 40.33 41.33 C

600 ppm B 44.47 42.32 43.40 B

1200 ppm B 47.45 44.58 46.02 A

Mean (P) 44.75 A 42.41 B

163










densities on leaf manganese content (µg g-1 DW) of cotton (2014)








at squaring

MC application

at flowering

Mean (B)

Control 39.08 42.56 41.58 41.08 C

600 ppm B 41.83 44.82 43.63 43.43 B

1200 ppm B 43.34 47.02 45.13 45.16 A

Mean (MC) 41.42 C 44.80 A 43.45 B


25 cm 15 cm

Control 42.53 39.63 41.08 C

600 ppm B 45.28 41.57 43.43 B

1200 ppm B 46.39 43.94 45.16 A

Mean (P) 44.73 A 41.71 B


at squaring

MC application

at flowering

Mean (B)

Control 51.04 50.59 50.73 50.79 A

600 ppm B 49.28 44.97 46.44 46.90 B

1200 ppm B 47.01 42.40 43.36 44.26 C

Mean (MC) 49.11 A 45.99 B 46.84 B


25 cm 15 cm

Control 52.88 48.69 50.79 A

600 ppm B 48.95 44.84 46.90 B

1200 ppm B 46.49 42.03 44.26 C

Mean (P) 49.44 A 45.19 B

164










densities on seed manganese content (µg g-1 DW) of cotton (2014)








at squaring

MC application

at flowering

Mean (B)

Control 53.89 50.60 52.44 52.31 A

600 ppm B 50.13 48.50 50.00 49.54 B

1200 ppm B 49.18 45.44 45.68 46.77 C

Mean (MC) 51.07 A 48.18 B 49.37 AB


25 cm 15 cm

Control 53.45 51.17 52.31 A

600 ppm B 51.17 47.92 49.54 B

1200 ppm B 48.70 44.83 46.77 C

Mean (P) 51.11 A 47.97 B


at squaring

MC application

at flowering

Mean (B)

Control 21.82 20.65 21.09 21.18 A

600 ppm B 20.54 19.56 20.19 20.10 B

1200 ppm B 19.81 18.39 18.87 19.02 C

Mean (MC) 20.72 A 19.53 B 20.05 AB


25 cm 15 cm

Control 22.08 20.29 21.18 A

600 ppm B 20.87 19.33 20.10 B

1200 ppm B 20.06 17.98 19.02 C

Mean (P) 21.01 A 19.20 B

165










densities on leaf iron content (µg g-1 DW) of cotton (2014)








at squaring

MC application

at flowering

Mean (B)

Control 22.38 21.43 21.66 21.82 A

600 ppm B 21.21 20.26 20.64 20.70 B

1200 ppm B 20.05 18.78 19.34 19.39 C

Mean (MC) 21.21 A 20.16 B 20.55 AB


25 cm 15 cm

Control 22.51 21.13 21.82 A

600 ppm B 21.57 19.84 20.70 B

1200 ppm B 20.04 18.74 19.39 C

Mean (P) 21.37 A 19.90 B


25 cm 15 cm

Control 166.09 160.18 163.14 C

600 ppm B 178.24 171.67 174.95 B

1200 ppm B 188.31 183.01 185.66 A

Mean (P) 177.55 A 171.62 B


at squaring

MC application

at flowering

Mean (B)

Control 156.13 160.45 158.79 158.46 C

600 ppm B 164.73 169.11 168.53 167.46 B

1200 ppm B 168.32 179.65 172.22 173.40 A

Mean (MC) 163.06 B 169.74 A 166.51 AB

166






densities on seed iron content (µg g-1 DW) of cotton (2014)


B: Boron; HSD for MC = 5.7863, HSD for B = 5.7863.










25 cm 15 cm

Control 162.12 154.79 158.46 C

600 ppm B 171.55 163.37 167.46 B

1200 ppm B 176.30 170.50 173.40 A

Mean (P) 169.99 A 162.89 B


at squaring

MC application

at flowering

Mean (B)

Control 167.60 171.71 169.60 169.64 C

600 ppm B 181.02 186.25 184.95 184.07 B

1200 ppm B 188.14 196.96 196.22 193.77 A

Mean (MC) 178.92 B 184.97 A 183.59 AB


25 cm 15 cm

Control 173.68 165.60 169.64 C

600 ppm B 188.02 180.12 184.07 B

1200 ppm B 196.88 190.66 193.77 A

Mean (P) 186.19 A 178.79 B


at squaring

MC application

at flowering

Mean (B)

Control 155.04 158.66 161.98 158.56 C

600 ppm B 164.07 169.65 170.65 168.13 B

1200 ppm B 168.63 183.49 176.92 176.35 A

Mean (MC) 162.58 B 170.60 A 169.85 A

167






25 cm 15 cm

Control 163.06 154.05 158.56 C

600 ppm B 170.27 165.98 168.13 B

1200 ppm B 178.84 173.86 176.35 A

Mean (P) 170.72 A 164.63 B

168

seed Fe content, during both years. However, leaf Fe content was improved only during 2015,

as compared to control. It was noticed that application of mepiquat chloride at squaring stage

caused greatest increase in leaf (4%) and seed Fe contents (3-5%), as compared to control.

Furthermore, application of mepiquat chloride at flowering stage produced similar results for

seed Fe contents during both years, while, for leaf Fe during 2015 only (Tables 4.156a, 4.157a,

4.158a). Conversely, sowing the crop at higher planting density lead to a decrease in leaf and

seed Fe contents by 3-4 and 4%, respectively, during both years (Tables 4.155, 4.156b, 4.157b,

4.158b).

4.1.16. Discussion

Boron application extolled the macronutrients (N, P and K) uptake and translocation in

cotton plants as detected by leaf and seed nutrients contents and the contents of these nutrients

increased with increase in B application rate. Boron application enhances the uptake and

translocation of N directly by exerting positive effect on activation of enzymes involved in N

metabolism and/or indirectly by promoting and regulating the entrance of substrate through

cellular membranes to interiorof cell (Ruiz et al., 1998). Boron has been found to have

synergistic effect with P and that might be due to its positive effect on P assimilation (Ahmed

et al., 2011). Similarly, B has been found to have a positive correlation with K that is function

of hyperpolarization of cell membranes by B resulting in enhanced accumulation of K in cells

(Schon et al., 1990). López-Lefebre et al. (2002) reported an increase in N, P and K uptake and

translocation in tobacco and cotton, respectively. In present study, mepiquat chloride

application enhanced the contents of N, P and K in leaf and seed tissues of cotton, across all B

treatments. It has been observed that uptake of nutrients is affected by root growth of plants

(Newman and Andrews, 1973). The enhanced N, P and K contents in leaf and seed tissues by

mepiquat chloride application is attributed to improved root growth, CO2 assimilation and

photosynthetic rate, and assimilate partitioning (Zhao and Oosterhuis, 2000; Duan et al., 2004;

Gwathmey and Clement, 2010). Sawan (2013) noticed extolled N and K contents in cotton

plants in response to mepiquat chloride application. Furthermore, Khan et al. (2005) reported

that increase in the N recovery efficiency by PGR application was related to enhanced plant

growth, leaf CO2 exchange rate (CER), and uptake and accumulation of N. On the other hand

increasing the planting density resulted in a decrease in uptake and translocation of N, P and

K. This might be attributed to higher inter-plant competition among plants for available

nutrients in the soil. Similar results were reported by Yan et al. (2017) that increasing the

planting density decreased the N uptake and NUE in maize.

169

The contents of micronutrients viz. B, Zn and Fe in leaves and seed of cotton was

increased in response to B application; however, the Mn showed a negative relation with B.

Foliar applied B and mepiquat chloride significantly interacted in improving the uptake and

translocation of B. The improved B contents may be due to direct increase in B in leaf and seed

tissues fed through foliar application. Whereas, mepiquat chloride application further improved

the leaf and seed tissue B contents which may be due to its positive interaction with B in

enhancing the root growth as well as assimilate partitioning (Duan et al., 2004; Zhao and

Oosterhuis, 2000); moreover, mepiquat chloride has been found to increase the transpiration

rate (Zhao and Oosterhuis, 2000) which may be the reason of enhanced boron uptake and

translocation because B is transported from roots to other plant parts through transpiration

stream (Mengel and Kirkby, 2001). Similar results were reported by Zhao and Oosterhuis

(2002) that B application resulted in exhilaration of B concentration in different cotton plant

parts and highest concentration was observed in leaves followed by other parts. However, no

previous report is available showing the increased uptake and translocation of B by mepiquat

chloride for comparison.

The results indicate that foliar B and mepiquat chloride exerted a positive effect on the

uptake as well as translocation of micronutrients except Mn. The decrease in uptake and

translocation of Mn may be attributed to its antagonistic effect with B (Mouhtaridou et al.,

2004). Studies have revealed the positive effect of B nutrition on Zn and Fe. Ahmed et al.

(2011) reported that B application enhanced concentration of Zn and Fe, while, decreased

concentration of Mn in leaf and seed tissues in cotton. Present study results showed that

mepiquat chloride application enhanced the contents of micronutrients except Mn in leaf and

seed tissues of cotton across all B treatments; however, the mepiquat chloride treatment at both

growth stages did not differ among each other. The improvement of micronutrients viz. Zn and

Fe by mepiquat chloride might be due to better root growth and enhanced assimilation rate.

Uptake and translocation of B was increased by mepiquat chloride application which might be

the reason of decreased Mn content due to their antagonistic effect with each other.

Furthermore, the range of deficiency and toxicity of micronutrients in plants is very low and

plants develop mechanisms to keep them in balance (Mengel and Kirkby, 2001; Miwa and

Fujiwara, 2010b). This seems to be the reason that why there was no difference between

mepiquat chloride treatment at squaring and flowering stage regarding micronutrients.

The uptake and translocation of micronutrients (B, Zn, Fe and Mn) in response to

planting density showed the similar trend as showed for macronutrients i.e. contents of

170

nutrients in leaf and seed of cotton decreased at higher planting density. This might be

attributed to decreased root growth of plants grown at higher planting density due to higher

competition among plants for space which ultimately reduces nutrient uptake and physiological

use efficiency (Jiang et al., 2013).

4.1.17. Cotton seed nutritional quality

Cotton seed oil content, protein content, ash content, oil yield and protein yield was

significantly affected by B, mepiquat chloride and planting, density, during both years. Oil,

protein and ash contents did not differ significantly by the interactive effects between B and

mepiquat chloride, B and planting density, mepiquat chloride and planting density as well as

three way interaction among B, mepiquat chloride and planting density, during both years

(Tables 4.159, 4.160). However, the interactive effects between B and mepiquat chloride, and

B and planting density were significant for oil and protein yield; while, interactive effects of

mepiquat chloride with planting density, and interaction among B, mepiquat chloride and

planting density was non-significant, during both years (Tables 4.159, 4.160).

The results exhibited that application of B improved the oil (4-5%), protein (4-5%) and

ash contents (5-6%) in cotton seed, as compared to control during both years. The highest

cotton seed oil, protein and ash contents were recorded by the foliar application of 1200 ppm

B and it was statistically at par with the effect of 600 ppm B solution, during both years (Tables

4.161a-4.166a). Similarly, application of mepiquat chloride improved the oil (5-6%), protein

(4%) and ash contents (7%) during both years with maximum increase occurring by the effect

of mepiquat chloride application at squaring stage, as compared to control. However, the effect

of mepiquat chloride application at flowering stage was statistically similar, during both years

(Table 4.161a-4.166a). On the other hand, increasing the planting density decreased the cotton

seed oil (4-5%), protein (2%) and ash contents (3%), during both years (Tables 4.161b-4.166b).

Cotton seed oil and protein yield was improved by application of B and mepiquat

chloride alone as well as in combination, during both years. However, the effect of foliar B and

mepiquat chloride in combination was greater than their application in alone. It was observed

that application of 1200 ppm B in combination with mepiquat chloride application at squaring

stage increased the oil yield (41-42%) and protein yield (38-43%) to a maximum level.

However, the effect of 1200 ppm B in combination with mepiquat chloride application at

flowering stage produced statistically similar results for protein yield, during both years (Tables

4.167a-4.170a). Furthermore, increasing the planting density resulted in enhanced oil and

protein yield as compared to lower planting density. Foliar application of B and planting

171


boron at various planting densities on cotton seed nutritional quality (2014)


Table 4.160: Analysis of variance for influence of foliar applied mepiquat chloride and boron at

various planting densities on cotton seed nutritional quality (2015)



Mean sum of squares

Oil

content

Protein

content

Ash

content

Oil yield Protein

yield

Replications 2 3.677 0.101 0.003 1626.5 289.7

Boron (B) 2 2.509** 3.666** 0.362** 13577.7** 15888.7** Mepiquat chloride (M) 2 3.577** 2.787** 0.509** 17360.3** 17415.0** Planting density (P) 1 11.491** 2.734* 0.204** 16607.6** 27246.7** B×M 4 0.087ns 0.080ns 0.033ns 995.6* 1126.2** B×P 2 0.046ns 0.043ns 0.037ns 1014.7* 738.0* M×P 2 0.257ns 0.002ns 0.022ns 225.3ns 63.7ns B×M×P 4 0.012ns 0.182ns 0.035ns 45.4ns 219.0ns Error 34 0.403 0.494 0.052 273.2 181.5

Total 53


Mean sum of squares

Oil

content

Protein

content

Ash

content

Oil yield Protein

yield

Replications 2 0.82706 0.70419 0.02172 60.2 173.2 Boron (B) 2 3.71989** 3.45469** 0.23921* 11716.7** 12393.8** Mepiquat chloride (M) 2 6.12876** 3.17125** 0.42569** 14631.5** 12931.7**

Planting density (P) 1 9.24214** 2.52202* 0.25352* 3227.3** 7019.4** B×M 4 0.24570ns 0.01819ns 0.01936ns 619.3** 660.4** B×P 2 0.00754ns 0.01365ns 0.01740ns 594.9* 606.2* M×P 2 0.03790ns 0.00816ns 0.00637ns 21.2ns 38.9ns B×M×P 4 0.08550ns 0.04465ns 0.03882ns 37.9ns 25.7ns Error 34 0.51782 0.52174 0.04748 132.9 157.4 Total 53

172


densities on cotton seed oil content (%) (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 18.72 19.76 19.28 19.25 B

600 ppm B 19.38 20.08 19.89 19.78 A

1200 ppm B 19.43 20.30 20.20 19.98 A

Mean (MC) 19.18 B 20.04 A 19.79 A


25 cm 15 cm

Control 19.72 18.79 19.25 B

600 ppm B 20.29 19.27 19.78 A

1200 ppm B 20.39 19.57 19.98 A

Mean (P) 20.13 A 19.21 B


at squaring

MC application

at flowering

Mean (B)

Control 17.72 19.10 18.70 18.51 B

600 ppm B 18.66 19.58 19.03 19.09 AB

1200 ppm B 18.68 19.81 19.72 19.40 A

Mean (MC) 18.36 B 19.49 A 19.15 A


25 cm 15 cm

Control 18.91 18.11 18.51 B

600 ppm B 19.53 18.66 19.09 AB

1200 ppm B 19.81 19.00 19.40 A

Mean (P) 19.41 A 18.59 B

173


densities on cotton seed protein content (%) (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 19.43 20.36 19.85 19.88 B

600 ppm B 20.01 20.61 20.31 20.31 AB

1200 ppm B 20.31 21.12 20.92 20.78 A

Mean (MC) 19.91 B 20.70 A 20.36 AB


25 cm 15 cm

Control 20.09 19.67 19.88 B

600 ppm B 20.49 20.13 20.31 AB

1200 ppm B 21.06 20.50 20.78 A

Mean (P) 20.55 A 20.10 B


at squaring

MC application

at flowering

Mean (B)

Control 19.01 19.80 19.39 19.40 B

600 ppm B 19.54 20.35 19.92 19.93 AB

1200 ppm B 19.78 20.68 20.35 20.27 A

Mean (MC) 19.44 B 20.28 A 19.89 AB


25 cm 15 cm

Control 19.64 19.16 19.40 B

600 ppm B 20.15 19.72 19.93 AB

1200 ppm B 20.46 20.08 20.27 A

Mean (P) 20.08 A 19.65 B

174


densities on cotton seed ash content (%) (2014)
















at squaring

MC application

at flowering

Mean (B)

Control 4.09 4.52 4.47 4.36 B

600 ppm B 4.42 4.60 4.56 4.53 AB

1200 ppm B 4.44 4.73 4.75 4.64 A

Mean (MC) 4.31 B 4.62 A 4.59 A


25 cm 15 cm

Control 4.48 4.24 4.36 B

600 ppm B 4.58 4.47 4.53 AB

1200 ppm B 4.67 4.60 4.64 A

Mean (P) 4.58 A 4.44 B


at squaring

MC application

at flowering

Mean (B)

Control 4.08 4.44 4.24 4.25 B

600 ppm B 4.23 4.48 4.39 4.37 AB

1200 ppm B 4.29 4.58 4.58 4.48 A

Mean (MC) 4.20 B 4.50 A 4.40 A


25 cm 15 cm

Control 4.29 4.21 4.25 B

600 ppm B 4.43 4.30 4.37 AB

1200 ppm B 4.58 4.38 4.48 A

Mean (P) 4.44 A 4.30 B

175


densities on cotton seed oil yield (kg ha-1) (2014)



= 31.572.









= 22.025.




B: Boron; HSD for P = 6.3692, HSD for B = 9.4197, HSD for P×B interaction = 16.404.


at squaring

MC application

at flowering

Mean (B)

Control 283.2 e 327.5 d 311.9 de 307.5 C

600 ppm B 313.0 de 363.5 bc 339.1 cd 338.5 B

1200 ppm B 312.9 de 402.8 a 371.3 ab 362.3 A

Mean (MC) 303.0 C 364.6 A 340.8 B


25 cm 15 cm

Control 291.2 d 323.9 bc 307.5 C

600 ppm B 327.8 c 349.2 b 338.5 B

1200 ppm B 336.8 bc 387.9 a 362.3 A

Mean (P) 318.6 B 353.7 A


at squaring

MC application

at flowering

Mean (B)

Control 251.9 e 294.9 cd 279.1 d 275.3 C

600 ppm B 280.2 d 331.9 b 304.8 c 305.6 B

1200 ppm B 282.3 d 356.4 a 339.3 ab 326.0 A

Mean (MC) 271.5 C 327.7 A 307.7 B


25 cm 15 cm

Control 265.8 d 284.8 c 275.3 C

600 ppm B 304.3 b 306.9 b 305.6 B

1200 ppm B 313.6 b 338.4 a 326.0 A

Mean (P) 294.6 B 310.0 A

176


densities on cotton seed protein yield (kg ha-1) (2014)



= 25.736.









= 23.964.




B: Boron; HSD for P = 6.9300, HSD for B = 10.249, HSD for P×B interaction = 17.848.


at squaring

MC application

at flowering

Mean (B)

Control 293.8 d 337.8 c 321.2 c 317.6 C

600 ppm B 323.6 c 373.4 b 346.5 c 347.8 B

1200 ppm B 327.3 c 419.5 a 384.3 b 377.0 A

Mean (MC) 314.9 C 376.9 A 350.6 B


25 cm 15 cm

Control 296.5 d 338.7 c 317.6 C

600 ppm B 331.0 c 364.7 b 347.8 B

1200 ppm B 347.6 bc 406.5 a 377.0 A

Mean (P) 325.0 B 369.9 A


at squaring

MC application

at flowering

Mean (B)

Control 270.3 e 306.1 cd 289.0 de 288.5 C

600 ppm B 293.7 de 345.1 b 319.2 c 319.3 B

1200 ppm B 299.3 cd 372.0 a 350.7 ab 340.7 A

Mean (MC) 287.8 C 341.1 A 319.6 B


25 cm 15 cm

Control 275.9 d 301.0 c 288.5 C

600 ppm B 314.2 bc 324.4 b 319.3 B

1200 ppm B 324.1 b 357.2 a 340.7 A

Mean (P) 304.8 B 327.6 A

177

density interactively improved the oil yield (16-18 and 19-20% at lower and higher planting

density, respectively) and protein yield (17 and 19-20% at lower and higher planting density,

respectively), as compared to control. Highest oil yield and protein yield was observed by

application of 1200 ppm B at higher planting density (Tables 4.167b-4.170b).

4.1.18. Discussion

The nutritional quality of cotton seed was improved by B and mepiquat chloride

application; though the improvement was not much pronounced. The improvement in seed ash,

oil and protein contents by B application might be due to improved C and N assimilation and

metabolism (Ahmed et al., 2014). It is evident from present study results exhibiting the

improved chlorophyll content, and N contents in leaves and seed by B application indicating

enhanced uptake and translocation. Bellaloui et al. (2015) reported improved cotton seed

protein and oil contents in response to B application. The improvement in seed protein content

by mepiquat chloride application is attributed to its role in protein synthesis through enhanced

conversion of amino acids in to protein (Wang and Chen, 1984); whereas, the increase in oil

content by mepiquat chloride application may be attributed to improved assimilation and

translocation of photosynthates (Zhao and Oosterhuis, 2000; Gwathmey and Clement, 2010).

Similar increase in protein and oil contents was reported by Sawan et al. (2007). Higher

planting density caused a reduction in cotton seed nutritional quality as compared to lower

planting density. This might be attributed to decrease in N uptake and translocation due to

higher inter-plant competition. Furthermore, the chlorophyll contents were decreased at higher

planting density that might have resulted in decreased photo-assimilation and assimilate

translocation leading to decreased cotton seed nutritional quality at higher planting density.

Similarly, Sawan et al. (1993) reported a decrease in oil and protein contents in response to

increase in planting density.

Application of B and mepiquat chloride exaggerated the oil and protein yield, as

compared to control. Higher cotton seed oil and protein yield might be due to higher yield, oil

and protein contents by B and mepiquat chloride application. Results of present study, indicate

that application of mepiquat chloride is an important management strategy to enhance the

cotton seed oil and protein yield under both B deficient and adequate conditions. Similarly,

Sawan et al. (2001) reported higher oil and protein yield by mepiquat chloride application

under adequate N and Zn conditions, as compared to deficient conditions. Increasing the

planting density increased the oil and protein yield and it was associated with higher cotton

seed yield as compared to lower planting density.

178


The results revealed that NUE of B was improved by foliar application of B and

mepiquat chloride at both planting density. Moreover, increasing the planting density further

improved the NUE of B. Although, sole application of B and enhanced the NUE as compared

to control; however, application of B along with mepiquat chloride caused more increase in

NUE relative to their controls, during both years. It was observed that at both plating densities

mepiquat chloride application enhanced the NUE of B though their interaction was non-

significant. At both planting densities application of 1200 ppm B in combination with mepiquat

chloride application at squaring stage increased the NUE than other treatments. However,

during 2014 the highest NUE of B (1.25) was observed when 1200 ppm B solution was applied

in combination with mepiquat chloride application at squaring stage at higher planting density,

while during 2015, highest NUE of B (1.20) was observed by application of same combination

of B and mepiquat chloride at lower planting density (Figure 4.13).

4.1.20. Critical value of boron

The relationship between relative seed cotton yield (95% of highest yield) and B

contents in leaves for the years 2014 and 2015 showed that critical value of B varied by foliar

application of B, mepiquat chloride application and increasing the planting density. It was

observed critical value of B was increased by application of mepiquat chloride while decreased

by increasing the planting density. The critical values of B with control (no mepiquat chloride),

mepiquat chloride application at squaring stage and mepiquat chloride application at flowering

stage at lower planting density were 34, 45 and 43 µg g-1 dry leaves, respectively, while at

higher planting density the critical values were 31, 45, 41 µg g-1 dry leaves, respectively (Figure

4.14).

4.1.21. Boron fertilizer requirement

The relationship between relative seed cotton yield (95% of highest yield) and foliar

applied B for the years 2014 and 2015 showed that the foliar B fertilizer requirement of cotton

crop was increased by application of mepiquat chloride and increasing the planting density. It

was observed that at lower planting density the foliar B fertilizer required with control (no

mepiquat chloride), mepiquat chloride application at squaring stage and mepiquat chloride

application at flowering stage was 155 480 and 510 ppm B ha-1, respectively, while at higher

planting density it was 420, 1020 and 1015 ppm B ha-1, respectively (Figure 4.15).

179

Nu

trie

nt

use

eff

icie

ncy


planting densities on nutrient use efficiency of cotton; M0: Control, M1: Mepiquat

chloride application at squaring stage, M2: Mepiquat chloride application at flowering

stage

0.70

0.80

0.90

1.00

1.10

1.20

1.30

M0 M1 M2 M0 M1 M2

25 cm 15 cm

600 ppm 1200 ppm

0.70

0.80

0.90

1.00

1.10

1.20

1.30

M0 M1 M2 M0 M1 M2

25 cm 15 cm

600 ppm 1200 ppm (b) 2015

(a) 2014

180

R

ela

tiv

e s

eed

co

tto

n y

ield

(%

)

Rela

tiv

e s

eed

co

tto

n y

ield

(%

)

Leaf boron concentration (µg g

-1 DW) Leaf boron concentration (µg g

-1 DW)

Figure 4.14: Relationship between boron contents in leaves and relative seed cotton

yield in response to foliar applied mepiquat chloride and boron at various planting

densities; M0: control, M1: mepiquat chloride application at squaring, M2: mepiquat

chloride application at flowering; P1: 25 cm, P2: 15 cm

(a) M0+P1 (b) M0+P2

(c) M1+P1 (d) M1+P2

(e) M2+P1 (f) M2+P2

M1

181

R

ela

tiv

e s

eed

co

tto

n y

ield

(%

)

Rela

tiv

e s

eed

co

tto

n y

ield

(%

)

Foliar applied boron (ppm solution) Foliar applied boron (ppm solution)

Figure 4.15: Relationship between boron application rate and relative seed cotton yield;

M0: control, M1: mepiquat chloride application at squaring, M2: mepiquat chloride

application at flowering; P1: 25 cm, P2: 15 cm

(a) M0+P1 (b) M0+P2

(c) M1+P1 (d) M1+P2

(e) M2+P1 (f) M2+P2

M1

182

4.1.22. Discussion

The results revealed that NUE for B was enhanced by foliar application of B. However,

application of mepiquat chloride along with foliar applied B enhanced the NUE of B manifolds

than sole application of B at both planting densities. This might be attributed to improved B

uptake and translocation from indigenous soil nutrient pool and/or applied through foliar

application. This is further evident from enhanced critical value of B that mepiquat chloride

application increased the seed cotton yield by increasing the B uptake and accumulation in

cotton leaves. As discussed previously, that mepiquat chloride application improves the root

growth as well as assimilate and nutrient partitioning which results in efficient utilization of

applied nutrients (Zhao and Oosterhuis, 2000; Duan et al., 2004; Gwathmey and Clement,

2010). Mepiquat chloride associated increase in B use efficiency can further be explained on

the basis of improved lint yield, cotton seed yield and seed B contents. This shows that

mepiquat chloride enhanced the translocation of B to developing bolls which ultimately led to

enhanced production of cotton seed and lint. This also indicates that mepiquat chloride

enhanced the utilization of B for seed and lint production due to which NUE of B was enhanced.

Similar, results were reported by Yang et al. (2014) that mepiquat chloride application

enhanced the K use efficiency and they explained it on the basis of enhanced K uptake and

partitioning. In this study, increasing the planting density increased the NUE of B which is

attributed to greater uptake of B per unit area with minimum losses of applied nutrient. Yan et

al. (2017) reported that increasing the planting density increased the N use efficiency to a limit

and then further increase in planting density decreased the N use efficiency.

The critical value of B was increased by application of mepiquat chloride and enhancing

planting density. It has been observed that critical value of B vary with varying the factors that

affect the B uptake and translocation such as water, soil type, soil texture and soil reaction,

organic matter, crop and soil management practices, plant spacing, microbial activity, plant

species, cultivar etc. (Sims and Johnson, 1991; Nabi et al., 2006; Barker and Pilbeam, 2007).

Therefore, variation in critical value of B by mepiquat chloride and planting density can be

explained on the basis of modification in uptake and utilization ability of plants. The decrease

in critical value by planting density might be associated with higher inter-plant competition

that led to efficient utilization of limited nutrient resources by plants for yield formation. On

the other hand, mepiquat chloride associated increase in critical value might be due to enhanced

uptake of B that led to luxury consumption i.e. more B uptake than increase in yield. This might

183

have happened due to improved cotton root growth by mepiquat chloride that enhanced the B

uptake along with applied B though foliar fertilization (Duan et al., 2004).

The B fertilizer requirement through foliar application was also increased by mepiquat

chloride application and higher planting density. Greater fertilizer requirement due to mepiquat

chloride application might be due to higher uptake and translocation of B required for

improving the crop yield. This also leads to the conclusion that with increased photo-

assimilation and assimilate partitioning due to modulation of vegetative and reproductive

growth by mepiquat chloride the limited supply of nutrient can’t be kept up for improving the

crop yield. Whereas, increased demand for foliar B fertilizer at higher planting density might

be due to greater requirement of B by higher number of plants per unit area.

4.1.23. Soil bioassay

4.1.23.1. Emergence and seedling growth of progeny

The final emergence, emergence index, root length and shoot length was significantly

affected by foliar applied B, mepiquat chloride and planting density, while, the interactive

effects between B and mepiquat chloride, B and panting density, mepiquat chloride and plating

density and three way interaction among B, mepiquat chloride and planting density was non-

significant during both years. However, the mean emergence time significantly differed by the

influence of foliar applied B and mepiquat chloride during 2015, and foliar applied B and

planting density during 2016. Whereas, the effect of planting density during 2015, mepiquat

chloride during 2016, and interactions between B and mepiquat chloride, B and planting

density, mepiquat chloride and planting density as well as three way interaction among B,

mepiquat chloride and planting density was non-significant during both years (Tables 4.171,

4.172).

Foliar application of B on maternal plants resulted in improved final emergence

percentage with highest value (67 and 72% during 2015 and 2016, respectively) occurring by

application of 1200 ppm B solution and it was followed by application of 600 ppm B solution,

during both years (4.173a, 4.174a). Likewise, mepiquat chloride treatment enhanced the final

emergence, as compared to control. The highest final emergence percentage (66 and 72%

during 2015 and 2016, respectively) was caused by application of mepiquat chloride at

squaring stage; however, mepiquat chloride application at flowering produced similar results,

during both years (4.173a, 4.174a). On the other hand, increasing the planting density resulted

in a decrease in final emergence of progeny seedlings (6% less during both years), as compared

to higher planting density (4.173b, 4.174b). The mean emergence time was decreased by the

184

Table 4.171: Analysis of variance for maternal induced changes in emergence and

seedling growth of cotton progeny in response to foliar applied mepiquat chloride and








Mean sum of squares

Final

emergence

percentage

Mean

emergence

time

Emergence

index

Root

length

Shoot

length

Boron (B) 2 235.19** 0.490** 0.258** 2.535** 17.024** Mepiquat chloride (M) 2 207.41* 0.329** 0.201** 2.030** 11.941** Planting density (P) 1 535.19** 0.011ns 0.277** 4.145** 21.219** B×M 4 7.41ns 0.015ns 0.007ns 0.186ns 1.386ns B×P 2 1.85ns 0.041ns 0.002ns 0.009ns 0.161ns

M×P 2 7.41ns 0.003ns 0.002ns 0.112ns 0.064ns B×M×P 4 7.41ns 0.003ns 0.003ns 0.035ns 0.263ns Error 36 29.63 0.021 0.013 0.234 1.792 Total 53


Mean sum of squares

Final

emergence

percentage

Mean

emergence

time

Emergence

index

Root

length

Shoot

length

Boron (B) 2 372.222** 0.166* 0.112** 2.595** 8.072* Mepiquat chloride (M) 2 272.222** 0.083ns 0.135** 2.221** 9.531** Planting density (P) 1 474.074** 0.301* 0.377** 2.779** 10.463* B×M 4 11.111ns 0.020ns 0.004ns 0.124ns 0.401ns B×P 2 1.852ns 0.008ns 0.0001ns 0.256ns 0.556ns

M×P 2 12.963ns 0.010ns 0.0001ns 0.212ns 0.538ns B×M×P 4 7.407ns 0.003ns 0.002ns 0.183ns 0.469ns Error 36 46.296 0.044 0.016 0.107 1.773 Total 53

185

Table 4.173a: Maternal induced changes in final emergence percentage (%) of cotton

progeny in response to foliar applied mepiquat chloride and boron at various planting

densities (2015)



Table 4.173b: Maternal induced changes in final emergence percentage (%) of cotton


densities (2015)



Table 4.174a: Maternal induced changes in final emergence percentage (%) of cotton


densities (2016)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for MC = 5.5450, HSD for B = 5.5450.

Table 4.174b: Maternal induced changes in final emergence percentage (%) of cotton


densities (2016)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; P: Planting density, B: Boron; HSD for P = 3.7516, HSD for B = 5.5450.


at squaring

MC application

at flowering

Mean (B)

Control 56.67 61.67 60.00 59.44 B 600 ppm B 60.00 66.67 63.33 63.33 AB 1200 ppm B 61.67 70.00 68.33 66.67 A

Mean (MC) 59.44 B 66.11 A 63.89 AB


25 cm 15 cm

Control 62.22 56.67 59.44 B 600 ppm B 66.67 60.00 63.33 AB 1200 ppm B 70.00 63.33 66.67 A Mean (P) 66.30 A 60.00 B


at squaring

MC application

at flowering

Mean (B)

Control 60.00 66.67 61.67 62.78 B 600 ppm B 65.00 73.33 68.33 68.89 A 1200 ppm B 66.67 75.00 73.33 71.67 A Mean (MC) 63.89 B 71.67 A 67.78 AB


25 cm 15 cm

Control 65.56 60.00 62.78 B 600 ppm B 72.22 65.56 68.89 A 1200 ppm B 74.44 68.89 71.67 A

Mean (P) 70.74 A 64.81 B

186

Table 4.175: Maternal induced changes in mean emergence time (days) of cotton progeny

in response to foliar applied mepiquat chloride and boron at various planting densities

(2015)



Table 4.176: Maternal induced changes in mean emergence time (days) of cotton progeny

in response to foliar applied mepiquat chloride and boron at various planting densities (2016)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for B = 0.1155, HSD for P = 0.1155.

Table 4.177a: Maternal induced changes in emergence index of cotton progeny in

response to foliar applied mepiquat chloride and boron at various planting densities

(2015)



Table 4.177b: Maternal induced changes in emergence index of cotton progeny in


(2015)




at squaring

MC application

at flowering

Mean (B)

Control 4.88 4.67 4.75 4.77 A 600 ppm B 4.66 4.35 4.50 4.50 B 1200 ppm B 4.64 4.37 4.37 4.46 B

Mean (MC) 4.73 A 4.46 B 4.54 B


25 cm 15 cm

Control 4.97 5.14 5.06 A 600 ppm B 4.85 5.02 4.94 AB 1200 ppm B 4.81 4.92 4.87 B Mean (P) 4.88 B 5.03 A


at squaring

MC application

at flowering

Mean (B)

Control 1.21 1.38 1.29 1.29 B 600 ppm B 1.34 1.56 1.44 1.45 A 1200 ppm B 1.38 1.62 1.58 1.53 A Mean (MC) 1.31 B 1.52 A 1.44 A


25 cm 15 cm Control 1.36 1.23 1.29 B

600 ppm B 1.53 1.36 1.45 A 1200 ppm B 1.59 1.46 1.53 A Mean (P) 1.49 A 1.35 B

187

Table 4.178a: Maternal induced changes in emergence index of cotton progeny in


(2016)


Table 4.178b: Maternal induced changes in emergence index of cotton progeny in


(2016)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; P: Planting density, B: Boron;

HSD for P = 0.0695, HSD for B = 0.1027.

Table 4.179a: Maternal induced changes in root length (cm) of cotton progeny in response

to foliar applied mepiquat chloride and boron at various planting densities (2015)



Table 4.179b: Maternal induced changes in root length (cm) of cotton progeny in response





at squaring

MC application

at flowering

Mean (B)


Mean (MC) 1.35 B 1.52 A 1.44 AB


25 cm 15 cm Control 1.43 1.27 1.35 B

600 ppm B 1.53 1.36 1.44 AB 1200 ppm B 1.60 1.43 1.51 A Mean (P) 1.52 A 1.35 B


at squaring

MC application

at flowering

Mean (B)



25 cm 15 cm

Control 6.89 6.36 6.63 B 600 ppm B 7.42 6.82 7.12 A 1200 ppm B 7.63 7.10 7.36 A Mean (P) 7.31 A 6.76 B

188

Table 4.180a: Maternal induced changes in root length (cm) of cotton progeny in response



Table 4.180b: Maternal induced changes in root length (cm) of cotton progeny in response



Table 4.181a: Maternal induced changes in shoot length (cm) of cotton progeny in


(2015)



Table 4.181b: Maternal induced changes in shoot length (cm) of cotton progeny in


(2015)




at squaring

MC application

at flowering

Mean (B)



25 cm 15 cm

Control 6.30 6.11 6.20 B 600 ppm B 7.05 6.42 6.73 A 1200 ppm B 7.21 6.67 6.94 A Mean (P) 6.85 A 6.40 B


at squaring

MC application

at flowering

Mean (B)

Control 18.67 19.45 19.02 19.05 B 600 ppm B 19.44 20.96 20.41 20.27 A 1200 ppm B 19.49 21.95 21.47 20.97 A Mean (MC) 19.20 B 20.79 A 20.30 AB


25 cm 15 cm Control 19.66 18.43 19.05 B

600 ppm B 21.00 19.54 20.27 A 1200 ppm B 21.51 20.43 20.97 A Mean (P) 20.72 A 19.47 B

189

Table 4.182a: Maternal induced changes in shoot length (cm) of cotton progeny in


(2016)


Table 4.182b: Maternal induced changes in shoot length (cm) of cotton progeny in


(2016)



at squaring

MC application

at flowering

Mean (B)


Mean (MC) 17.45 B 18.90 A 18.30 AB


25 cm 15 cm

Control 17.73 17.23 17.48 B 600 ppm B 18.97 17.78 18.38 AB 1200 ppm B 19.27 18.31 18.79 A

Mean (P) 18.65 A 17.77 B

190

influence of B, as compared to control during both years. The minimum time (4.46 and 4.87

days during 2015 and 2016, respectively) was taken by progeny seedlings to emerge when the

maternal plants were treated with 1200 ppm B and it was followed by 600 ppm B (Tables

4.175, 4.176). The mepiquat chloride application to maternal plants decreased the mean

emergence time during 2015, as compared to control. The application of mepiquat chloride at

squaring stage was most effective with minimum mean emergence time (4.88 days) but

mepiquat chloride at flowering stage produced similar results (Tables 4.175). Similarly,

planting densities affected the mean emergence time only during 2015. Emergence was delayed

by approximately 0.2 days when the maternal plants were planted at higher density, as

compared to lower density (Table 4.176). Highest emergence index (1.53 and 1.51 during 2015

and 2016, respectively) was exhibited by application of 1200 ppm B solution to maternal plants

and 600 ppm B produced similar results, during both years (Tables 4.177a, 4.178a). Likewise,

mepiquat chloride treatment of maternal plants enhanced the emergence index, as compared to

control during both years. The highest emergence index (1.52 and 1.60 during 2015 and 2016,

respectively) was recorded by application of mepiquat chloride at squaring stage; however,

mepiquat chloride application at flowering produced similar results for these traits (Tables

4.177a, 4.178a). On the other hand, increasing the planting density resulted in a decrease in

emergence index (by ≈ 0.2), during both years (Tables 4.177b, 4.178b).

Foliar application of B on maternal plants resulted in improved seedling growth of

progeny. It was noticed that highest root length (11-12%) and shoot length (7-10%) was

exhibited by application of 1200 ppm B solution to maternal plants and it was followed by

application of 600 ppm B solution, during both years (Tables 4.179a, 4.180a, 4.181a, 4.182a).

Mepiquat chloride application at squaring stage on maternal plants enhanced the root length

(9-11%) and shoot length (8%) of progeny to maximum level; however, mepiquat chloride

application at flowering produced similar results for these traits, during both years (Tables

4.179a, 4.180a, 4.181a, 4.182a). However, higher planting density decreased the root length

(7-8%) and shoot length (5-6%) of offspring, during both years (Tables 4.179b, 4.180b, 4.181b,

4.182b).

4.1.23.2. Biomass accumulation in progeny seedlings

Production of fresh and dry biomass of roots and shoots as well as seedling vigour index

of progeny seedlings significantly differed by the influence of foliar application of B, mepiquat

chloride, panting density as well as interactive effect of B and mepiquat chloride on maternal

plants during both years; however, the interaction between B and planting density, mepiquat

191

chloride and planting density, and three way interaction among B, mepiquat chloride and

planting density was non-significant during both years. Nonetheless, root/shoot ratio did not

differ significantly by application of B, mepiquat chloride, panting density, and interactions


density, and three way interaction among B, mepiquat chloride and planting density, during

both years (Tables 4.183, 4.184).

The results revealed that application of B and mepiquat chloride alone as well as in

combination on maternal plants improved the fresh and dry biomass of roots and shoots, and

seedling vigour index of progeny seedlings, during both years. Maximum improvement in root

fresh (26-29%) and dry biomass (26-28%) as well as shoot fresh (25-27%) and dry weight (27-

28%), and seedling vigour index (45-47%) was caused by application of 1200 ppm B in

combination with mepiquat chloride application at squaring stage on maternal plants; while,

application of 1200 ppm B in combination with mepiquat chloride application at flowering

stage as well as 600 ppm B in combination with mepiquat chloride application at squaring stage

produced similar results, during both years (Tables 4.185a-4.196a). Maternal cotton plants

sown at higher planting density lead to a decrease in root fresh (10-12%) and dry weight (11-

18%), shoot fresh (4-6%) and dry biomass (8-10%) as well as seedling vigour index (14-15%),

as compared to control during both years (Tables 4.185b-4.196b).

4.1.24. Discussion

Soil bioassay showed that emergence and seedling vigour of cotton progeny was

enhanced by B and mepiquat chloride application on maternal plants. It was observed that B

and mepiquat chloride application lowered the time for mean emergence and improved the final

emergence and emergence index thus synergistically enhancing the seedling vigour. However,

planting of maternal cotton plants at higher planting density negatively affected the emergence

and seedling vigour of progeny. The improved final emergence, emergence time and seedling

vigour was associated with enhanced seed size and seed nutrient contents indicating that the

effect of maternal boron nutrition and mepiquat chloride is passed on to progeny through better

seed development and nutrient status, and vice versa for planting density.

Enhanced emergence and seedling vigour of cotton progeny by B application on

maternal plants is in agreement with suggestion that adequate nutrient supply is necessary for

better seed germination and vigour of crops (Welch, 1999; Dordas, 2006a,b). Moreover, B is

involved in the remobilization of nutrients stored in seed during the germination event (Bonilla

et al., 2004). It has also been found to modulate germination metabolism and translocation of

192

Table 4.183: Analysis of variance for maternal induced changes in seedling growth of

cotton progeny in response to foliar applied mepiquat chloride and boron at various




cotton progeny in response to foliar applied mepiquat chloride and boron at various




Mean sum of squares

Root

fresh

weight

Shoot

fresh

weight

Root dry

weight

Shoot dry

weight

Root/shoot Seedling

vigor

index

Boron (B) 2 1625.47** 331786** 26.940** 3227.73** 0.00091 611068**

Mepiquat chloride (M) 2 1386.31** 283717** 17.819** 3196.85** 0.00020ns 485628**

Planting density (P) 1 2419.91** 215306** 139.491** 5437.87** 0.00060ns 1089657**

B×M 4 116.00* 21024* 2.733** 242.19* 0.00035ns 35824*

B×P 2 24.18ns 4205ns 0.368ns 168.48ns 0.00005ns 5461ns

M×P 2 0.82ns 870ns 0.122ns 65.17ns 0.0002ns 5206ns

B×M×P 4 11.56ns 3859ns 0.262ns 60.43ns 0.0006ns 13112ns

Error 36 40.95 7799 0.664 79.23 0.0009 9280

Total 53


Mean sum of squares

Root

fresh

weight

Shoot

fresh

weight

Root dry

weight

Shoot dry

weight

Root/shoot Seedling

vigor

index

Boron (B) 2 1035.04** 189698** 16.8866** 2794.37** 0.00107ns 609283**


Planting density (P) 1 2745.34** 65711** 33.1193** 2793.46** 0.00067ns 813685**

B×M 4 96.06* 12530* 1.2724* 273.79* 0.00003ns 20979*

B×P 2 13.96ns 989ns 0.1668ns 6.69ns 0.00005ns 17115ns

M×P 2 8.05ns 1927ns 0.0282ns 16.87ns 0.00018ns 5272ns

B×M×P 4 52.12ns 452ns 0.0314ns 105.59ns 0.00007ns 16042ns

Error 36 31.31 4696 0.3988 71.14 0.00047 7083

Total 53

193

Table 4.185a: Maternal induced changes in root fresh weight (mg) of cotton progeny in


(2015)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for MC = 5.2148, HSD for B = 5.2148, HSD for MC×B = 12.179.

Table 4.185b: Maternal induced changes in root fresh weight (mg) of cotton progeny in


(2015)


HSD for P = 3.5282, HSD for B = 5.2148.

Table 4.186a: Maternal induced changes in root fresh weight (mg) of cotton progeny in


(2016)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for MC = 4.5603, HSD for B = 4.5603, HSD for B×MC interaction = 10.650.

Table 4.186b: Maternal induced changes in root fresh weight (mg) of cotton progeny in


(2016)



at squaring

MC application

at flowering

Mean (B)

Control 112.78 d 121.51 cd 119.95 cd 118.08 C 600 ppm B 120.95 cd 138.03 ab 132.01 bc 130.33 B 1200 ppm B 121.72 cd 145.95 a 142.70 ab 136.79 A

Mean (MC) 118.48 B 135.16 A 131.55 A


25 cm 15 cm Control 124.07 112.09 118.08 C

600 ppm B 138.36 122.30 130.33 B 1200 ppm B 142.84 130.73 136.79 A Mean (P) 135.09 A 121.70 B


at squaring

MC application

at flowering

Mean (B)

Control 103.29 d 109.95 cd 108.35 cd 107.20 C 600 ppm B 109.22 cd 125.70 ab 117.15 bc 117.36 B 1200 ppm B 109.80 cd 130.64 a 125.65 ab 122.03 A Mean (MC) 107.44 C 122.10 A 117.05 B


25 cm 15 cm


Mean (P) 122.66 A 108.40 B

194

Table 4.187a: Maternal induced changes in shoot fresh weight (mg) of cotton progeny in


(2015)



Table 4.187b: Maternal induced changes in shoot fresh weight (mg) of cotton progeny in


(2015)



Table 4.188a: Maternal induced changes in shoot fresh weight (mg) of cotton progeny in

response to foliar applied mepiquat chloride and boron at various planting densities (2016)


Table 4.188b: Maternal induced changes in shoot fresh weight (mg) of cotton progeny in




at squaring

MC application

at flowering

Mean (B)

Control 1688.89 c 1808.33 c 1777.17 c 1758.13 C 600 ppm B 1799.44 c 2064.44 ab 1995.67 b 1953.19 B 1200 ppm B 1816.67 c 2148.22 a 2092.87 ab 2019.25 A

Mean (MC) 1768.33 B 2007.00 A 1955.23 A


25 cm 15 cm

Control 1807.04 1709.22 1758.13 C 600 ppm B 2032.48 1873.89 1953.19 B 1200 ppm B 2080.48 1958.02 2019.25 A Mean (P) 1973.33 A 1847.04 B


at squaring

MC application

at flowering

Mean (B)

Control 1485.26 c 1593.00 bc 1548.77 bc 1542.34 C 600 ppm B 1576.45 bc 1799.46 a 1644.81 b 1673.57 B 1200 ppm B 1604.59 bc 1854.57 a 1774.97 a 1744.71 A Mean (MC) 1555.43 C 1749.01 A 1656.18 B


25 cm 15 cm


195

Table 4.189a: Maternal induced changes in root dry weight (mg) of cotton progeny in


(2015)



Table 4.189b: Maternal induced changes in root dry weight (mg) of cotton progeny in


(2015)



Table 4.190a: Maternal induced changes in root dry weight (mg) of cotton progeny in



Table 4.190b: Maternal induced changes in root dry weight (mg) of cotton progeny in




at squaring

MC application

at flowering

Mean (B)

Control 14.50 d 15.41 cd 15.06 cd 14.99 C 600 ppm B 15.66 cd 17.63 ab 16.55 bc 16.61 B 1200 ppm B 15.49 cd 18.36 a 18.31 a 17.39 A

Mean (MC) 15.22 B 17.13 A 16.64 A


25 cm 15 cm



at squaring

MC application

at flowering

Mean (B)

Control 12.35 d 13.24 cd 12.87 cd 12.82 C 600 ppm B 13.06 cd 14.97 ab 13.96 bc 13.99 B 1200 ppm B 13.28 cd 15.76 a 15.18 ab 14.74 A Mean (MC) 12.89 C 14.66 A 14.00 B


25 cm 15 cm


196

Table 4.191a: Maternal induced changes in shoot dry weight (mg) of cotton progeny in


(2015)



Table 4.191b: Maternal induced changes in shoot dry weight (mg) of cotton progeny in


(2015)



Table 4.192a: Maternal induced changes in shoot dry weight (mg) of cotton progeny in


Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B:

Boron; HSD for MC = 6.8737, HSD for B = 6.8737, HSD for B×MC interaction = 16.053.

Table 4.192b: Maternal induced changes in shoot dry weight (mg) of cotton progeny in



HSD for P = 4.6505, HSD for B = 6.8737.


at squaring

MC application

at flowering

Mean (B)

Control 173.89 c 186.61 c 185.33 c 181.94 C 600 ppm B 185.02 c 211.60 ab 203.48 b 200.03 B 1200 ppm B 186.02 c 222.83 a 215.42 ab 208.09 A

Mean (MC) 181.64 B 207.01 A 201.41 A


25 cm 15 cm



at squaring

MC application

at flowering

Mean (B)

Control 152.87 d 163.96 cd 160.67 cd 159.17 C

600 ppm B 161.03 cd 184.13 ab 175.22 bc 173.46 B 1200 ppm B 163.01 cd 194.61 a 194.36 a 183.99 A Mean (MC) 158.97 B 180.90 A 176.75 A


25 cm 15 cm


197

Table 4.193: Maternal induced changes in root/shoot ratio of cotton progeny in response



Table 4.194: Maternal induced changes in root/shoot ratio of cotton progeny in response



Table 4.195a: Maternal induced changes in seedling vigour index of cotton progeny in


(2015)



Table 4.195b: Maternal induced changes in seedling vigour index of cotton progeny in


(2015)




25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application at

squaring

MC

application at

flowering

Mean

(B)

Control 0.34 0.35 0.35 0.34 0.35 0.35 0.35

600 ppm B 0.35 0.36 0.35 0.35 0.35 0.35 0.35

1200 ppm B 0.35 0.36 0.36 0.35 0.34 0.36 0.35

Mean (MC×P) 0.35 0.36 0.35 0.35 0.34 0.35

Mean (P) 0.35 0.35


25 cm 15 cm

Control MC

application

at squaring

MC

application

at flowering

Control MC

application at

squaring

MC

application at

flowering

Mean

(B)

Control 0.35 0.36 0.36 0.35 0.36 0.35 0.36

600 ppm B 0.36 0.38 0.37 0.36 0.36 0.36 0.37

1200 ppm B 0.36 0.38 0.38 0.36 0.37 0.36 0.37

Mean (MC×P) 0.36 0.37 0.37 0.36 0.36 0.36

Mean (P) 0.37 0.36


at squaring

MC application

at flowering

Mean (B)

Control 1422.39 f 1617.67 de 1537.28 ef 1525.78 C 600 ppm B 1571.02 def 1886.95 bc 1747.71 cd 1735.23 B

1200 ppm B 1618.21 de 2069.40 a 1991.62 ab 1893.08 A Mean (MC) 1537.21 C 1858.01 A 1758.87 B


25 cm 15 cm


Mean (P) 1860.08 A 1575.98 B

198

Table 4.196a: Maternal induced changes in seedling vigour index of cotton progeny in



Table 4.196b: Maternal induced changes in seedling vigour index of cotton progeny in




at squaring

MC application

at flowering

Mean (B)

Control 1372.10 d 1618.38 bc 1461.89 cd 1484.12 C 600 ppm B 1548.92 bc 1917.18 a 1713.01 b 1726.37 B 1200 ppm B 1607.04 bc 2020.81 a 1907.48 a 1845.11 A Mean (MC) 1509.35 C 1852.12 A 1694.13 B


25 cm 15 cm Control 1573.53 1394.72 1484.12 C 600 ppm B 1876.60 1576.14 1726.37 B

1200 ppm B 1973.73 1716.49 1845.11 A Mean (P) 1807.95 A 1562.45 B

199

carbohydrates from the endosperm to developing embryo (Cresswell and Nelson, 1972).

Likewise, improved emergence and seedling vigour of cotton progeny by mepiquat chloride

application through improved seed size and seed nutrient contents might be due to enhanced

assimilate partitioning of photo-assimilates and nutrients to the developing seed (Sawan et al.,

2009). It has been found that application of mepiquat chloride decreases the assimilate

partitioning to main stem, branches and growing points, while, increasing the partitioning to

reproductive structures and roots (Wang et al., 1995) which might be the reason of improved

emergence and seedling vigour. Higher planting density resulted in the production of poor

quality seed in terms of emergence and seedling vigor. This might be attributed to decreased

seed size by increasing the planting density. Similar results were reported by Merfield et al.

(2010) that increase in planting density lead to a reduction in germination and seedling vigour

of carrot.

Maternal B and mepiquat chloride application resulted in improved growth and

development of progeny seedlings. This shows that better growth of progeny plants by maternal

B and mepiquat chloride application was due to enhanced assimilate and nutrient translocation

(especially B) to developing seeds that produced healthy and vigorous seedlings, as compared

to control. Boron enhances the plant growth through improved cell division and elongation.

Boron is required to regulate the cell wall structure and functioning thus regulating the cell

elongation (Miwa and Fujiwara, 2010a). In present study, biomass production and

accumulation in roots and shoots of progeny was improved by maternal B and mepiquat

chloride application and they both significantly interacted in this regard. Boron deficiency

causes a reduction in dry matter production and accumulation (Zhao and Oosterhuis, 2003);

however, B nutrition has been observed to improve the dry matter production and accumulation

in plants (Ahmed et al., 2011). Qiong et al. (2002) reported that B application significantly

improved the leaf photosynthetic activity, which consequently lead to greater accumulation of

dry matter in peanut plants. The increase in photo-assimilation and translocation to developing

seeds results in improved seed size and ultimately enhanced seedling growth and biomass

production in progeny seedlings (Dordas, 2006a). Likewise, Sawan et al. (2009) reported that

mepiquat chloride application improved the seedling fresh and dry weights in response to

residual effect of mepiquat chloride on cotton. On the contrary, increasing the planting density

of maternal plants decreased the progeny seedlings’ growth and biomass production. It has

been observed that at higher planting density the seed size and surface area is reduced which

might be due to inadequate availability of photo-assimilates to the developing seeds (Xiao-yu

200

et al., 2016). Moreover, more time was taken by progeny seedlings grown from seed obtained

from maternal plants sown at higher density which might be the reason of decreased seedling

growth and biomass production.

4.1.25. Regression and correlation analysis

Nodes above white flower (NAWF) and NACB were positively associated with mean

maturity days while negatively associated with earliness index. The coefficients of

determination explained 86-94 and 87-93% variation in mean maturity days and earliness index

owing to NAWF, during 2014 and 2015, respectively (Tables 4.197, 4.198). Nonetheless,

variation in mean maturity days and earliness index due to NACB was 91-92 and 84-94% as

explained by this relationship (Tables 4.197, 4.198). Mean maturity days were negatively

correlated with earliness index and production rate index, during both years. The coefficients

of determination explained upto 99% variation in mean maturity days and earliness index,

during both years (Tables 4.197, 4.198). The corresponding values amounted 81-94 and 88-

98% for variation between mean maturity days and production rate index, during 2014 and

2015, respectively (Tables 4.197, 4.198).

The CGR was positively correlated with boll weight and seed cotton yield, during both

years. The corresponding values of variation for boll weight and seed cotton yield were 49-50

and 48-49%, respectively, during 2014, while, 33-51 and 36-59%, respectively, during 2015

owing to CGR (Tables 4.197, 4.198). Leaf total chlorophyll contents were positively correlated

with NAR and the corresponding value of variation for NAR was 59-66 and 74-75% during

2014 and 2015, respectively (Tables 4.197, 4.198). Whereas, the NAR was significantly

correlated with boll weight and seed cotton yield, during both years. The coefficients of

determination explained 46-48 and 63-66% variation in boll weight and seed cotton yield,

respectively, during 2014, and 58-65 and 69-85%, respectively, during 2015 due to NAR

(Tables 4.197, 4.198). Reproductive dry matter and TDM accumulation was positively

correlated with seed cotton yield, during both years. The variation in seed cotton yield due to

reproductive dry matter was 87-88 and 85-93% during 2014 and 2015, respectively (Tables

4.197, 4.198). The boll weight, boll density and number of seeds per boll were strongly

correlated with seed cotton yield, during both years. It was observed that the variation in seed

cotton yield due to boll weight, boll density and number of seeds was 85-87, 92-94 and 80-

83%, respectively, during 2014, while 84-89, 96-97 and 82-84%, respectively, during 2015

(Tables 4.197, 4.198). Leaf B contents were also significantly and positively correlated with

seed cotton yield. The coefficient of determination explained 84-86 and 83-89% variation in

201

Table 4.197: Coefficients of determination (R2) and correlation coefficients (r) denoting

goodness of fit and association strength between different variables (2014)

ns: non-significant; *: Significant at p 0.1; **: Significant at p 0.05; ***: significant at p 0.01

X-variable Y-variable 25 cm 15 cm

R2 r R

2 r

NAWF Mean maturity days 0.94 0.97*** 0.86 0.93***

NAWF Earliness index 0.94 -0.97*** 0.86 -0.93***

NACB Mean maturity days 0.92 0.96*** 0.91 0.95***

NACB Earliness index 0.92 -0.96*** 0.91 -0.95***

Mean maturity days Earliness index 0.99 -0.99*** 0.99 -0.99***

Mean maturity days Production rate index 0.94 -0.97*** 0.81 -0.90***

CGR Boll weight 0.49 0.70* 0.50 0.71*

CGR Seed cotton yield 0.49 0.70* 0.48 0.69*

Total chlorophyll NAR 0.66 0.81** 0.59 0.77**

NAR Boll weight 0.46 0.68* 0.48 0.69*

NAR Seed cotton yield 0.63 0.79* 0.66 0.81**

Reproductive DM Seed cotton yield 0.87 0.93*** 0.88 0.94***

TDM Seed cotton yield 0.44 0.66ns 0.45 0.67*

Boll weight Seed cotton yield 0.87 0.93** 0.85 0.92***

Boll density Seed cotton yield 0.92 0.96*** 0.94 0.97***

No. of seeds Seed cotton yield 0.80 0.89** 0.83 0.91***

Leaf boron content Seed cotton yield 0.84 0.92*** 0.86 0.93***

No. of seeds Ginning out turn 0.61 0.78** 0.70 0.84**

Seed boron content Ginning out turn 0.76 0.87*** 0.84 0.92***

No. of seeds Final emergence % 0.80 0.89*** 0.79 0.89***

Seed index Final emergence % 0.83 0.91*** 0.91 0.95***

Seed boron content Final emergence % 0.85 0.92*** 0.88 0.94***

Seed boron content Root dry biomass 0.88 0.94*** 0.86 0.93***

Seed boron content Shoot dry biomass 0.89 0.94*** 0.88 0.94***

202


goodness of fit and association strength between different variables (2015)

ns: non-significant; *: Significant at p 0.1; **: Significant at p 0.05; ***: significant at p 0.01

X-variable Y-variable 25 cm 15 cm

R2 r R

2 r







CGR Boll weight 0.51 0.71** 0.33 0.57ns

CGR Seed cotton yield 0.56 0.75** 0.36 0.60ns

Total chlorophyll NAR 0.75 0.87** 0.74 0.86**

NAR Boll weight 0.65 0.81*** 0.58 0.76**

NAR Seed cotton yield 0.85 0.92*** 0.69 0.83**


TDM Seed cotton yield 0.52 0.72*** 0.32 0.57ns

Boll weight Seed cotton yield 0.89 0.94*** 0.84 0.92***

Boll density Seed cotton yield 0.96 0.98*** 0.97 0.98***

No. of seeds Seed cotton yield 0.84 0.92*** 0.82 0.91***


No. of seeds Ginning out turn 0.78 0.88*** 0.62 0.79**







203

seed cotton yield due to leaf B contents, during 2014 and 2015, respectively (Tables 4.197,

4.198).

Number of seeds and seed B contents were significantly and positively correlated

with ginning out turn, during both years, and the corresponding values of variation in

ginning out turn by number of seeds was 61-70 and 62-78%, during 2014 and 2015

respectively, while due to seed B contents was 76-84 and 79-88%, during 2014 and 2015,

respectively (Tables 4.197, 4.198). Similarly, number of seeds, seed index and seed B

content was positively associated with final emergence of progeny seedlings, and the

corresponding values of variation as determined by coefficient of determination were 79-

80, 83-91 and 85-89%, respectively, during 2014, and 80-92, 90-95 and 83-87%,

respectively, during 2015 (Tables 4.197, 4.198). A significant and positive correlation of

seed B content was observed with root and shoot dry biomass of progeny seedlings, during

both years. Root dry biomass and shoot dry biomass varied by 86-92 and 83-89%,

respectively, during 2014, and 81-94 and 85%, respectively, during 2015 (Tables 4.197,

4.198).

4.1.26. Economic analysis

Foliar application of B and mepiquat chloride at both planting densities improved

the economic benefits and BCR. It was observed that increasing the planting density

resulted in an increase in net returns and BCR; however, the greatest increase in net returns

and BCR was occurred when B was applied in combination with mepiquat chloride at

higher planting density. Highest net returns (worth Rs. 113596) and BCR (1.83) was

recorded by application of 1200 ppm B solution plus mepiquat chloride application at

squaring stage at higher planting density (Table 4.199). This is attributed to increase in seed

cotton yield by interactive effect of foliar applied B and mepiquat chloride at higher

planting density. Higher seed cotton yield resulted in an increase in net profits that

ultimately led to improved BCR. Moreover, the marginal analysis further revealed that

MRR was enhanced by application of 1200 ppm B plus mepiquat chloride at squaring stage

at both planting densities. However, among all treatments, the combination of 1200 ppm B

plus mepiquat chloride at squaring stage at higher planting density produced the highest

MRR (2022%) (Table 4.200). This suggests that this combination can be adopted at farmer

level to acquire higher benefits. Similar results have been reported by Ahmed et al. (2013)

by B application, and Prakash and Prasad (2000) by a plant growth retardant (chlormequat

chloride) application, and Ehsanullah et al. (2017) at higher planting density of cotton.

204

Table 4.199: Economic analysis

Adjusted yield: 10% less than actual yield; Income was estimated by using the prevailing market prices for seed cotton in Pakistan; P: Planting

density; B: Boron; MC: Mepiquat chloride; BCR: Benefit cost ratio

Treatments Yield

(kg ha-1

)

Adjusted

yield

(kg ha-1

)

Gross

income

(Rs.)

Fixed cost

(Rs.)

Variable

cost

(Rs.)

Total cost

(Rs.)

Net returns

(Rs.)

BCR

P = 25 cm Control 2234 2010 167522 118135 11673 129808 37715 1.29 600 ppm B 2449 2204 183665 118135 13006 131141 52524 1.40 1200 ppm B 2395 2156 179659 118135 13031 131166 48494 1.37 MC at squaring 2420 2178 181480 118135 13148 131283 50198 1.38 MC at flowering 2369 2133 177709 118135 13021 131156 46553 1.35 600 ppm B + MC at squaring 2803 2523 210252 118135 15270 133405 76847 1.58

600 ppm B + MC at flowering 2615 2354 196143 118135 14402 132537 63606 1.48 1200 ppm B + MC at squaring 2917 2626 218805 118135 15840 133975 84830 1.63 1200 ppm B + MC at flowering 2738 2465 205379 118135 15330 133464 71915 1.54

P = 15 cm

Control 2479 2231 185953 118135 14210 132345 53609 1.41 600 ppm B 2635 2372 197651 118135 15293 133428 64223 1.48 1200 ppm B 2738 2464 205371 118135 15977 134112 71259 1.53 MC at squaring 2738 2464 205369 118135 15991 134126 71243 1.53 MC at flowering 2667 2401 200048 118135 15710 133845 66203 1.49 600 ppm B + MC at squaring 2953 2658 221499 118135 17324 135459 86040 1.64 600 ppm B + MC at flowering 2809 2528 210694 118135 16738 134873 75821 1.56 1200 ppm B + MC at squaring 3346 3012 250962 118135 19231 137366 113596 1.83

1200 ppm B + MC at flowering 3144 2829 235789 118135 18516 136651 99138 1.73

205

Table 4.200: Marginal analysis

P: Planting density; B: Boron; MC: Mepiquat chloride

Treatments Variable

cost

(Rs.)

Marginal

variable

cost (Rs.)

Net

benefits

(Rs.)

Marginal

net benefit

(Rs.)

Marginal

rate of

return (%)

P = 25 cm Control 11673 - 155849 - - 600 ppm B 13006 1333 170659 14810 1111 MC at flowering 13021 15 164688 - D 1200 ppm B 13031 10 166629 - D MC at squaring 13148 117 168333 - D 600 ppm B + MC at flowering 14402 1254 181741 11082 883

600 ppm B + MC at squaring 15270 868 194982 13241 1526 1200 ppm B + MC at flowering 15330 60 190050 - D 1200 ppm B + MC at squaring 15840 511 202965 7983 1563

P = 15 cm

Control 14210 - 171743 - - 600 ppm B 15293 1083 182358 10615 980 MC at flowering 15710 417 184338 1980 474 1200 ppm B 15977 267 189394 5056 1894 MC at squaring 15991 14 189377 - D 600 ppm B + MC at flowering 16738 747 193956 4579 613 600 ppm B + MC at squaring 17324 585 204175 10219 1745 1200 ppm B + MC at flowering 18516 1192 217273 13098 1098

1200 ppm B + MC at squaring 19231 715 231731 14458 2022

206

4.2. Effect of foliar applied mepiquat chloride and soil applied boron on cotton

4.2.1. Plant growth and architecture

Soil application of B and foliar applied mepiquat chloride altered the plant growth

and architecture of cotton. Plant height, number of main stem nodes, internodes length,

number of monopodial and sympodial branches, and node for first effective sympodial

branch was significantly affected by B and mepiquat chloride; however, the interactive

effect of soil applied B and foliar applied mepiquat chloride was non-significant, during

both years. The NAWF and NACB were significantly affected by B, mepiquat chloride and

their interaction during both years (Tables 4.201, 4.202).

Soil applied B enhanced the plant growth as compared to control, during both years.

It was observed that application of 2.5 kg B ha -1 caused greatest increase in plant height

(12-13%). Nonetheless, the effect of 1.5-2 kg B ha-1 on plant height was statistically similar

(Tables 4.203, 4.204). On the other hand foliar applied mepiquat chloride decreased the

plant height (12-15%), as compared to control during both years. The greatest decrease in

plant height was noticed by application of mepiquat chloride at squaring stage during both

years (Tables 4.203, 4.204). Main stem nodes were increased by soil applied boron (5%),

as compared to control during both years. Highest number of main stem nodes were

observed by the application of 2.5 kg B ha -1. Nonetheless, the effect of 1-2 kg B ha-1 on

number of main stem nodes was similar (Tables 4.205, 4.206). However, greatest decrease

in number of main stem nodes (7%) was exhibited by application of mepiquat chloride at

squaring stage, as compared to control during both years. Whereas the effect of mepiquat

chloride at flowering stage was statistically at par regarding number of main stem nodes

during 2014 (Tables 4.205, 4.206). Soil application of B caused an increase in internodes

length (6-8%), as compared to control and 2.5 kg B ha-1 produced the longest internodes

length while 1.5-2 kg B ha-1 produced similar results for internodes length (Tables 4.207,

4.208). Internodes length was decreased by application of mepiquat chloride (6-8%), as

compared to control during both years. The shortest internodes were noticed by application

of mepiquat chloride at squaring stage (Tables 4.207, 4.208).

Soil B nutrition increased the number of monopodial (10-11%) and sympodial

branches (6-7%), as compared to control during both years. It was observed that application

of 2.5 kg B ha-1 caused greatest increase in number of monopodial and sympodial branches.

Nonetheless, the effect of 1-2 kg B ha-1 on number of monopodial and sympodial branches

was statistically similar (Tables 4.209-4.212). Conversely, application of mepiquat chloride

decreased the number of monopodial (14-16%) and sympodial branches (8-9%), and

207

Table 4.201: Analysis of variance for influence of foliar application of mepiquat chloride and soil applied boron on agronomic



Table 4.202: Analysis of variance for influence of foliar application of mepiquat chloride and soil applied boron on agronomic




Mean sum of squares

Plant height

No. of nodes

Internodes length

No. of monopodial

branches

No. of sympodial

branches

Node for first effective

sympodial

branch

Nodes above white

flower

Nodes above

cracked

boll

Replications 2 32.580 1.839 0.007 0.010 2.756 0.140 0.057 0.120

Boron (B) 4 299.891** 3.467* 0.107** 0.065* 3.186* 0.429* 0.976** 0.577**


B×M 8 2.369ns 0.121ns 0.003ns 0.003ns 0.078ns 0.025ns 0.129* 0.093*

Error 28 20.948 1.083 0.018 0.017 0.946 0.138 0.042 0.032

Total 44


Mean sum of squares

Plant

height

No. of

nodes

Internodes

length

No. of

monopodial

branches

No. of

sympodial

branches

Node for

first effective

sympodial branch

Nodes

above white

flower

Nodes

above

cracked boll

Replications 2 12.05 0.067 0.012 0.317 1.506 0.489 0.002 0.104

Boron (B) 4 370.33** 4.575** 0.104** 0.130** 4.575** 1.605** 2.001** 1.200**


B×M 8 9.01ns 0.092ns 0.005ns 0.011ns 0.079ns 0.204ns 0.159* 0.108*

Error 28 27.20 1.061 0.016 0.024 1.107 0.261 0.065 0.037

Total 44

208

Table 4.203: Influence of foliar application of mepiquat chloride and soil applied

boron on plant height (cm) of cotton (2014)




boron on plant height (cm) of cotton (2015)




boron on number of main stem nodes of cotton (2014)




boron on number of main stem nodes of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 119.28 101.41 110.71 110.47 D 1 kg B ha

-1 123.95 106.24 113.87 114.69 CD

1.5 kg B ha-1

127.68 109.43 119.07 118.72 BC 2 kg B ha

-1 132.27 112.83 120.86 121.99 AB

2.5 kg B ha-1

135.90 115.40 123.76 125.02 A

Mean (MC) 127.82 A 109.06 C 117.65 B


at squaring

MC application

at flowering

Mean (B)

Control 135.06 118.18 131.51 128.25 C 1 kg B ha

-1 142.13 124.92 134.17 133.74 BC

1.5 kg B ha-1

146.46 129.00 135.75 137.07 AB 2 kg B ha

-1 153.10 133.92 141.69 142.90 A

2.5 kg B ha-1

153.25 133.40 143.94 143.53 A

Mean (MC) 146.00 A 127.89 C 137.41 B


at squaring

MC application

at flowering

Mean (B)

Control 33.33 30.50 31.50 31.78 B 1 kg B ha

-1 33.67 31.33 32.00 32.33 AB

1.5 kg B ha-1

34.00 31.33 32.67 32.67 AB 2 kg B ha

-1 34.50 32.17 32.67 33.11 AB

2.5 kg B ha-1

34.50 32.33 33.17 33.33 A

Mean (MC) 34.00 A 31.53 B 32.40 B


at squaring

MC application

at flowering

Mean (B)

Control 33.67 31.00 32.83 32.50 B 1 kg B ha

-1 34.50 32.17 33.33 33.33 AB

1.5 kg B ha-1

35.00 32.67 33.67 33.78 AB 2 kg B ha

-1 35.17 33.00 34.17 34.11 A

2.5 kg B ha-1

35.33 33.17 34.33 34.28 A Mean (MC) 34.73 A 32.40 C 33.67 B

209


boron on internodes length (cm) of cotton (2014)




boron on internodes length (cm) of cotton (2015)




boron on number of monopodial branches of cotton (2014)




boron on number of monopodial branches of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 3.58 3.32 3.52 3.47 C 1 kg B ha

-1 3.68 3.39 3.56 3.54 BC

1.5 kg B ha-1

3.75 3.49 3.65 3.63 ABC 2 kg B ha

-1 3.84 3.51 3.70 3.68 AB

2.5 kg B ha-1

3.94 3.57 3.73 3.75 A

Mean (MC) 3.76 A 3.46 C 3.63 B


at squaring

MC application

at flowering

Mean (B)

Control 4.01 3.81 4.01 3.94 B 1 kg B ha

-1 4.12 3.88 4.02 4.01 B

1.5 kg B ha-1

4.18 3.95 4.03 4.06 AB 2 kg B ha

-1 4.36 4.06 4.15 4.19 A

2.5 kg B ha-1

4.34 4.02 4.19 4.18 A

Mean (MC) 4.20 A 3.95 C 4.08 B


at squaring

MC application

at flowering

Mean (B)

Control 2.00 1.75 1.92 1.89 B 1 kg B ha

-1 2.08 1.75 1.92 1.92 AB

1.5 kg B ha-1

2.17 1.83 2.00 2.00 AB 2 kg B ha

-1 2.25 1.83 2.08 2.06 AB

2.5 kg B ha-1

2.25 1.92 2.08 2.08 A

Mean (MC) 2.15 A 1.82 C 2.00 B


at squaring

MC application

at flowering

Mean (B)

Control 2.67 2.25 2.58 2.50 C 1 kg B ha

-1 2.58 2.33 2.67 2.53 BC

1.5 kg B ha-1

2.83 2.42 2.67 2.64 ABC 2 kg B ha

-1 2.92 2.50 2.75 2.72 AB

2.5 kg B ha-1

3.00 2.50 2.83 2.78 A Mean (MC) 2.80 A 2.40 B 2.70 A

210


boron on number of sympodial branches of cotton (2014)




boron on number of sympodial branches of cotton (2015)




boron on node for first effective boll bearing (sympodial) branch of cotton (2014)




boron on node for first effective boll bearing (sympodial) branch of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 25.33 22.83 23.67 23.94 B 1 kg B ha

-1 25.83 23.50 24.17 24.50 AB

1.5 kg B ha-1

26.17 23.50 24.83 24.83 AB 2 kg B ha

-1 26.67 24.17 24.83 25.22 AB

2.5 kg B ha-1

26.67 24.50 25.17 25.44 A

Mean (MC) 26.13 A 23.70 B 24.53 B


at squaring

MC application

at flowering

Mean (B)

Control 25.67 23.00 24.67 24.44 B 1 kg B ha

-1 26.33 24.17 25.33 25.28 AB

1.5 kg B ha-1

26.83 24.67 25.67 25.72 AB 2 kg B ha

-1 27.00 25.00 26.17 26.06 A

2.5 kg B ha-1

27.17 25.17 26.33 26.22 A

Mean (MC) 26.60 A 24.40 C 25.63 B


at squaring

MC application

at flowering

Mean (B)

Control 7.63 7.10 7.40 7.38 A 1 kg B ha

-1 7.50 6.73 7.27 7.17 AB

1.5 kg B ha-1

7.12 6.77 7.03 6.97 AB 2 kg B ha

-1 7.00 6.63 6.93 6.86 AB

2.5 kg B ha-1

7.17 6.60 6.90 6.89 B

Mean (MC) 7.28 A 6.77 B 7.11 A


at squaring

MC application

at flowering

Mean (B)

Control 11.00 8.78 9.50 9.76 A 1 kg B ha

-1 10.00 8.56 9.56 9.37 AB

1.5 kg B ha-1

9.67 8.00 9.25 8.97 B 2 kg B ha

-1 9.44 8.00 9.25 8.90 B

2.5 kg B ha-1

9.56 7.74 8.81 8.70 B Mean (MC) 9.93 A 8.22 C 9.27 B

211

Table 4.215: Influence of foliar application of mepiquat chloride and soil applied boron on

nodes above white flower (NAWF) of cotton (2014)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for MC = 0.1859, HSD for B = 0.2825, HSD for MC×B interaction = 0.6221.


nodes above white flower (NAWF) of cotton (2015)



nodes above cracked boll (NACB) of cotton (2014)



nodes above cracked boll (NACB) of cotton (2015)


Boron; HSD for MC = 0.1739, HSD for B = 0.2644, HSD for MC×B interaction = 0.5823.


at squaring

MC application

at flowering

Mean (B)

Control 5.95 a 5.21 bcd 5.68 abc 5.61 A

1 kg B ha-1

5.82 ab 4.74 def 5.31 bcd 5.29 B 1.5 kg B ha

-1 5.67 abc 4.31 ef 5.15 cd 5.04 BC

2 kg B ha-1

5.64 abc 4.29 ef 4.80 de 4.91 C 2.5 kg B ha

-1 5.70 abc 4.14 f 4.51 ef 4.78 C

Mean (MC) 5.76 A 4.54 C 5.09 B


at squaring

MC application

at flowering

Mean (B)

Control 7.67 a 6.78 bcd 7.27 ab 7.24 A 1 kg B ha

-1 7.29 ab 6.61 bcd 6.93 a-d 6.95 AB

1.5 kg B ha-1

7.08 abc 6.33 cde 6.92 a-d 6.78 B 2 kg B ha

-1 6.92 a-d 5.59 ef 6.25 de 6.25 C

2.5 kg B ha-1

6.92 a-d 5.19 f 6.24 de 6.12 C Mean (MC) 7.17 A 6.10 C 6.72 B


at squaring

MC application

at flowering

Mean (B)

Control 4.85 a 4.35 a-d 4.43 abc 4.54 A 1 kg B ha

-1 4.74 a 4.09 bcd 4.37 a-d 4.40 AB

1.5 kg B ha-1

4.59 ab 3.87 de 4.33 a-d 4.26 B 2 kg B ha

-1 4.56 ab 3.43 e 3.99 cd 3.99 C

2.5 kg B ha-1

4.65 a 3.38 e 3.86 de 3.96 C Mean (MC) 4.68 A 3.82 C 4.20 B


at squaring

MC application

at flowering

Mean (B)

Control 6.36 a 5.68 bcd 5.99 abc 6.01 A 1 kg B ha

-1 6.12 ab 5.56 bcd 5.83 abc 5.84 A

1.5 kg B ha-1

5.91 abc 5.11 de 5.47 cd 5.49 B 2 kg B ha

-1 5.80 abc 4.67 ef 5.44 cd 5.30 BC

2.5 kg B ha-1

5.87 abc 4.43 f 5.10 de 5.13 C Mean (MC) 6.01 A 5.09 C 5.57 B

212

application of mepiquat chloride at squaring stage was most effective in this regard, during

both years. However, mepiquat chloride application at flowering stage produced similar

results, during 2014 (Tables 4.209-4.212).

Application of both B and mepiquat chloride decreased the node for first effective

sympodial branch, as compared to control during both years. The greatest decreased in node

for first effective sympodial branch (7-11%) was caused by application of 2.5 kg B ha-1 but

the effect of 1-2 kg B ha-1 was similar (Tables 4.213, 4.214). Similarly, mepiquat chloride

application at squaring stage caused maximum reduction in node for first effective

sympodial branch (7-17%), as compared to control during both years (Tables 4.213, 4.214).

The NAWF and NACB were decreased by soil application of B and foliar applied mepiquat

chloride as well as by their interaction, as compared to control during both years. The

greatest decrease in NAWF (30-32%) and NACB (30%) was caused when of 2.5 kg B ha-

1 was applied in combination with mepiquat chloride application at squaring stage during

both years. However, it was followed by 1.5-2 kg B ha-1 in combination with mepiquat

chloride application at squaring stage as well as 2.5 kg B ha-1 in combination with mepiquat

chloride application at flowering stage, during 2014. Whereas, during 2015 the effect of 2

kg B ha-1 in combination with mepiquat chloride application at squaring stage was similar

(Tables 4.215-4.218).

4.2.2. Discussion

Cotton is perennial in nature having indeterminate fruiting pattern and is cultivated

as annual crop. Therefore, the pattern of branching and fruiting is a major determent of crop

growth and yield in cotton. Thus, understanding effects of plant canopy architecture on

growth and yield of cotton can be very useful for successful management of crop growth

and breeding (Jost et al., 2006). Plant architecture is also of agronomic importance as its

management improves the photosynthesis, light use efficiency and nutrient use efficiency

(Zhao and Oosterhuis, 2000; Gonias et al., 2012; Li et al., 2017).

In this study, soil application of B improved the plant growth i.e. plant height,

number of main stem nodes, internodes length, and monopodial and sympodial branches

and the increase in growth was proportional to the dosage of B. Enhanced plant growth by

soil applied B might be attributed to its role in meristematic tissues (Marschner, 1995;

Barker and Pilbeam, 2007). Boron deficiency impairs the meristematic growth due to its

involvement in cell division and elongation (Dell and Huang, 1997; Miwa and Fujiwara,

2010b). Boron influences the cell elongation because it is involved in borate cross linking

of RG II pectic polysaccharide (Kobayashi et al., 1996; O’Neill et al., 2004). This RG II-

213

borate complex controls the tensile strength of cell walls (Ryden et al., 2003). Boron is also

involved in the regulation of genes that are involved in cell wall modification (Camacho-

Cristobal et al., 2008), thus affecting the cell wall loosening that is necessary for cell wall

elongation (Cosgrove, 1999). Besides of cross linking of pectins, B regulates the

functioning of cell membrane and metabolic activities (Bolanos et al., 2004), and is

structural component of cytoskeleton thus regulates the cell division (Bassil et al., 2004).

On the other hand, foliar application of mepiquat chloride altered the plant

architecture by reducing the plant growth attributes, at all levels of B. The decrease in

growth by mepiquat chloride is attributed to decrease in the biosynthesis and concentration

of gibberellic acid within plant cells which consequences in reduced cell wall plasticity and

cell size (Rademacher, 2000; Wang et al., 2014). In this study, application of mepiquat

chloride at squaring stage caused more reduction in growth as compared to mepiquat

chloride application at flowering stage. This is due to the fact that mepiquat chloride

application at squaring stage slowed down the growth of plants earlier and further the plants

receiving mepiquat chloride at flowering stage had already gained greater growth. The

results of this study are in consistence with Yeates et al. (2005); Nuti et al. (2006); Abbas

et al. (2010) and Mao et al. (2014) who reported a decrease in growth in response to

mepiquat chloride application at different growth stages with highest reduction caused by

mepiquat chloride application at seedling and squaring stages.

4.2.3. Phenological development

4.2.3.1. Calendar time

Commencement of squaring and boll maturation period were not significantly

differed by soil application of B, foliar applied mepiquat chloride and their interaction,

during both years. However, days to flowering and boll opening initiation, mean maturity

days, earliness index and production rate index was significantly affected by soil applied B

and foliar mepiquat chloride. Moreover, the interaction between soil applied B and foliar

mepiquat chloride was also significant for production rate index; while, non-significant for

days to flowering and boll opening initiation, mean maturity days and earliness index,


The results revealed that soil application of B caused an increase in earliness in

maturity by decreasing the days to commencement in flowering and boll opening, as

compared to control during both years. It was observed that maximum decrease in days for

initiation of flowering (3 and 2.7 days during 2014 and 2015, respectively) and boll opening

(3.5 and 3.8 days during 2014 and 2015, respectively) was occurred when the crop was

214

Table 4.219: Analysis of variance for influence of foliar application of mepiquat chloride and soil applied boron on phenology of cotton

(2014)


Table 4.220: Analysis of variance for influence of foliar application of mepiquat chloride and soil applied boron on phenology of cotton

(2015)



Mean sum of squares

Days to

squaring

Days to

flowering

Days to boll

opening

Boll

maturation

period

Mean

maturity

days

Earliness

index

Production

rate index

Replications 2 2.754 4.529 27.531 14.872 1.263 7.864 20.902 Boron (B) 4 0.833ns 13.898** 19.999* 0.756ns 6.359** 39.720** 22.758** Mepiquat chloride (M) 2 0.115ns 21.219** 28.611** 0.839ns 7.193** 44.964** 1.807** B×M 8 0.369ns 0.391ns 0.414ns 0.172ns 0.490ns 3.079ns 0.340** Error 28 1.964 3.373 5.143 3.069 1.261 7.872 20.902 Total 44


Mean sum of squares

Days to

squaring

initiation

Days to

flowering

initiation

Days to boll

opening

initiation

Boll

maturation

period

Mean

maturity

days

Earliness

index

Production

rate index

Replications 2 1.570 2.756 10.400 2.489 0.142 0.883 13.709 Boron (B) 4 0.059ns 9.786** 20.411** 2.208ns 4.930** 30.842* 23.191** Mepiquat chloride (M) 2 0.027ns 46.022** 50.117** 0.406ns 14.247** 88.998** 1.048** B×M 8 0.015ns 0.328ns 0.603ns 0.058ns 0.181ns 1.136ns 0.313** Error 28 1.492 1.910 4.489 2.792 1.209 7.578 13.709 Total 44

215


boron on days to squaring initiation of cotton (2014)


chloride, B: Boron.


boron on days to squaring initiation of cotton (2015)


chloride, B: Boron.


boron on days to flowering initiation of cotton (2014)




boron on days to flowering initiation of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 35.08 35.42 34.25 34.92 1 kg B ha

-1 34.92 34.25 34.92 34.69

1.5 kg B ha-1

34.25 34.15 34.35 34.25

2 kg B ha-1

34.25 34.08 34.25 34.19 2.5 kg B ha

-1 34.50 34.42 34.42 34.44

Mean (MC) 34.60 34.46 34.44


at squaring

MC application

at flowering

Mean (B)

Control 37.00 37.17 37.00 37.06 1 kg B ha

-1 37.10 36.97 36.93 37.00

1.5 kg B ha-1

37.00 37.17 37.03 37.07

2 kg B ha-1

36.83 36.90 36.87 36.87 2.5 kg B ha

-1 36.90 37.00 37.00 36.97

Mean (MC) 36.97 37.04 36.97


at squaring

MC application

at flowering

Mean (B)

Control 58.50 55.67 58.67 57.61 A 1 kg B ha

-1 57.33 55.33 57.10 56.59 AB

1.5 kg B ha-1

56.50 54.50 56.50 55.83 AB 2 kg B ha

-1 54.83 53.67 55.00 54.50 B

2.5 kg B ha-1

55.83 53.50 55.67 55.00 B Mean (MC) 56.60 A 54.53 B 56.59 A


at squaring

MC application

at flowering

Mean (B)

Control 60.17 57.50 60.17 59.28 A 1 kg B ha

-1 59.50 56.67 59.33 58.50 AB

1.5 kg B ha-1

58.50 55.67 58.50 57.56 AB 2 kg B ha

-1 57.50 54.67 57.67 56.61 B

2.5 kg B ha-1

58.83 54.67 58.50 57.33 B Mean (MC) 58.90 A 55.83 B 58.83 A

216


boron on days to boll opening initiation of cotton (2014)




boron on days to boll opening initiation of cotton (2015)




boron on boll maturation period of cotton (2014)


chloride, B: Boron.


boron on boll maturation period of cotton (2015)


chloride, B: Boron.


at squaring

MC application

at flowering

Mean (B)

Control 101.33 98.33 101.17 100.28 A 1 kg B ha

-1 100.50 98.00 99.93 99.48 AB

1.5 kg B ha-1

99.17 97.00 99.00 98.39 AB 2 kg B ha

-1 97.17 95.50 97.50 96.72 AB

2.5 kg B ha-1

98.67 95.33 97.67 97.22 B

Mean (MC) 99.37 A 96.83 B 99.05 A


at squaring

MC application

at flowering

Mean (B)

Control 104.83 102.00 104.67 103.83 A 1 kg B ha

-1 103.50 100.67 103.00 102.39 AB

1.5 kg B ha-1

102.33 99.33 102.17 101.28 AB 2 kg B ha

-1 101.17 98.00 101.00 100.06 B

2.5 kg B ha-1

102.50 97.67 101.67 100.61 B

Mean (MC) 102.87 A 99.53 B 102.50 A


at squaring

MC application

at flowering

Mean (B)

Control 42.83 42.67 42.50 42.67 1 kg B ha

-1 43.17 42.67 42.83 42.89

1.5 kg B ha-1

42.67 42.50 42.50 42.56 2 kg B ha

-1 42.33 41.83 42.50 42.22

2.5 kg B ha-1

42.83 41.83 42.00 42.22

Mean (MC) 42.77 42.30 42.47


at squaring

MC application

at flowering

Mean (B)

Control 44.67 44.50 44.50 44.56 1 kg B ha

-1 44.00 44.00 43.67 43.89

1.5 kg B ha-1

43.83 43.67 43.67 43.72 2 kg B ha

-1 43.67 43.33 43.33 43.44

2.5 kg B ha-1

43.67 43.00 43.17 43.28 Mean (MC) 43.97 43.70 43.67

217


boron on mean maturity days of cotton (2014)




boron on mean maturity days of cotton (2015)




boron on earliness index of cotton (2014)




boron on earliness index of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 143.14 141.26 142.03 142.14 A 1 kg B ha

-1 142.07 141.48 141.79 141.78 AB

1.5 kg B ha-1

141.41 140.64 141.45 141.16 AB 2 kg B ha

-1 140.79 139.53 140.77 140.36 B

2.5 kg B ha-1

141.14 138.93 140.65 140.24 B

Mean (MC) 141.71 A 140.37 B 141.34 AB


at squaring

MC application

at flowering

Mean (B)

Control 143.81 142.36 143.41 143.19 A 1 kg B ha

-1 143.16 141.67 142.83 142.55 AB

1.5 kg B ha-1

142.81 140.65 142.71 142.06 AB 2 kg B ha

-1 142.08 140.40 141.96 141.48 B

2.5 kg B ha-1

142.40 140.09 141.87 141.45 B

Mean (MC) 142.85 A 141.03 B 142.55 A


at squaring

MC application

at flowering

Mean (B)

Control 67.14 71.85 69.94 69.64 B 1 kg B ha

-1 69.82 71.31 70.53 70.55 AB

1.5 kg B ha-1

71.49 73.41 71.38 72.09 AB 2 kg B ha

-1 73.04 76.17 73.07 74.09 A

2.5 kg B ha-1

72.14 77.67 73.39 74.40 A

Mean (MC) 70.72 B 74.08 A 71.66 AB


at squaring

MC application

at flowering

Mean (B)

Control 65.48 69.10 66.47 67.02 B 1 kg B ha

-1 67.11 70.83 67.93 68.63 AB

1.5 kg B ha-1

67.97 73.37 68.23 69.86 AB 2 kg B ha

-1 69.80 74.00 70.10 71.30 A

2.5 kg B ha-1

69.00 74.77 70.33 71.37 A Mean (MC) 67.87 B 72.41 A 68.61 B

218


boron on production rate index of cotton (2014)





boron on production rate index of cotton (2015)





at squaring

MC application

at flowering

Mean (B)

Control 15.50 f 17.27 def 16.78 ef 16.52 D 1 kg B ha

-1 16.66 ef 17.52 de 17.43 de 17.20 CD

1.5 kg B ha-1

17.14 def 18.82 cd 17.97 cde 17.98 C 2 kg B ha

-1 17.77 cde 20.96 ab 19.37 bc 19.37 B

2.5 kg B ha-1

17.62 cde 22.30 a 20.74 ab 20.22 A

Mean (MC) 16.94 C 19.38 A 18.46 B


at squaring

MC application

at flowering

Mean (B)

Control 14.78 e 16.29 de 15.69 de 15.58 C 1 kg B ha

-1 15.41 de 17.01 cd 16.21 de 16.21 C

1.5 kg B ha-1

15.91 de 18.23 bc 16.93 cd 17.02 B

2 kg B ha-1

16.40 de 19.21 ab 18.30 bc 17.97 A 2.5 kg B ha

-1 16.21 de 20.28 a 19.30 a 18.60 A

Mean (MC) 15.74 C 18.20 A 17.28 B

219

treated with 2 kg B ha-1; However, the effect of 1-2.5 kg B ha-1 was statistically at par for

these traits during both years (Tables 4.223-4.226). Similarly, mepiquat chloride enhanced

the earliness in maturity by decreasing the days to flowering and boll opening initiation.

The greatest decrease in days to flowering (2 and 3 days during 2014 and 2015,

respectively) and boll opening (2.5 and 3.3 days during 2014 and 2015, respectively) was

caused by application of mepiquat chloride at squaring stage, during both years (Tables

4.223-4.226).

Mean maturity days were decreased and earliness index was increased by soil

application of B, as compared to control during both years. Application of 2.5 kg B ha -1

caused maximum reduction in mean maturity days (≈2 and 1.7 days during 2014 and 2015,

respectively) and increase in earliness index (6-7%). However, the effect of 1-2.5 kg B ha-

1 produced similar results (Tables 4.229-4.232). Similarly, mepiquat chloride application

decreased the mean maturity days and increased earliness index during both years. The

least mean maturity days (1 and 1.2 days during 2014 and 2015, respectively) and highest

earliness index (5-7%) was caused by application of mepiquat chloride at squaring stage,

during both years. However, mepiquat chloride application at flowering stage was

statistically similar for mean maturity days and earliness index during 2014 (Tables 4.229-

4.232).

The production rate index was exalted by soil application of B and foliar applied

mepiquat chloride alone but when B was applied in combination with mepiquat chloride

the production rate index was increased to a great extent, as compared to control during

both years. The results showed that application of 2.5 kg B ha-1 in combination with

mepiquat chloride application at squaring increased the production rate index most (37-

44%), while, the effect of 2.5 kg B ha-1 in combination with mepiquat chloride application

at flowering stage and 2 kg B ha-1 in combination with mepiquat chloride application at

squaring produced statistically similar results during both years (Tables 4.233, 4.234).


Heat units accumulation from sowing to squaring was not affected significantly by

soil applied B and foliar applied mepiquat chloride as well as their interaction, during both

years. However, heat unit accumulation form sowing to flowering, squaring to flowering

and sowing to boll opening were significantly affected by soil applied B and foliar applied

mepiquat chloride but their interaction was non-significant, during both years. Soil

application of B and foliar applied mepiquat chloride as well as their interaction did not

220

differ significantly for heat unit accumulation from flowering to boll opening, during both

years (Tables 4.235, 4.236).

Soil application of B decreased the accumulation of heat unit from sowing to

flowering (54 and 42 GDD during 2014 and 2015, respectively), squaring to flowering (41

and 39 GDD during 2014 and 2015, respectively) and sowing to boll opening (47 and 60

GDD during 2014 and 2015, respectively), as compared to control. It was observed that

minimum heat unit accumulation from sowing to flowering (998 and 921 GDD during 2014

and 2015, respectively), squaring to flowering (352 and 315 GDD during 2014 and 2015,

respectively) and sowing to boll opening (1700 and 1594 GDD during 2014 and 2015,

respectively) was occurred by application of 2 kg B ha-1. However, the effect of 1-2.5 kg B

ha-1 was statistically at par for heat unit accumulation, during both years (Tables 4.239-

4.244). Likewise, application of mepiquat chloride decreased the accumulation of heat unit

from sowing to flowering (36 and 48 GDD during 2014 and 2015, respectively), squaring

to flowering (33 and 49 GDD during 2014 and 2015, respectively) and sowing to boll

opening (33 and 54 GDD during 2014 and 2015, respectively), as compared to control.

Minimum heat unit accumulation from sowing to flowering (999 and 909 GDD during

2014 and 2015, respectively), squaring to flowering (347 and 300 GDD during 2014 and

2015, respectively) and sowing to boll opening (1702 and 1586 GDD during 2014 and

2015, respectively) was occurred by application of mepiquat chloride at squaring stage

(Tables 4.239-4.244).

4.2.4. Discussion

Crop phenological development determines the yield potential of a crop. The

phenological development in response to soil applied B and foliage applied mepiquat

chloride was assessed in terms of plant architectural modification (NAWF and NACB),

calendar time and thermal time.

The plant structural modifications were induced by soil application of B and foliage

applied mepiquat chloride that were used as an index to measure the crop maturity. It was

observed that B and mepiquat chloride significantly interacted in decreasing the NAWF

and NACB that are used as an index to measure the physiological cutout. In this study also,

the fact was proved that B is involved in reserve remobilization due to which earlier

physiological cutout occurred leading to enhanced earliness (Saleem et al., 2016b).

Furthermore, mepiquat chloride also enhances the reserve remobilization by altering the

balance from vegetative to reproductive growth (Zhao and Oosterhuis, 2000; Gwathmey

and Clement, 2010). Similarly, in this experiment it was observed that the vegetative dry

221

Table 4.235: Analysis of variance for influence of foliar application of mepiquat

chloride and soil applied boron on thermal time of cotton (2014)



chloride and soil applied boron on thermal time of cotton (2014)


Table 4.237: Influence of mepiquat chloride and boron on thermal time (GDD)

taken from sowing to square initiation of cotton

MC: Mepiquat chloride, B: Boron.

Table 4.238: Influence of mepiquat chloride and boron on thermal time (GDD)

taken from sowing to square initiation of cotton



Mean sum of squares

Sowing-squaring

Sowing-flowering

Squaring-flowering

Sowing-boll

opening

Flowering-boll

opening

Replications 2 909.96 1379.94 49.99 4731.01 2373.21

Boron (B) 4 266.08ns 4126.54** 2500.22** 3777.34* 144.81ns

Mepiquat chloride (M) 2 34.95ns 6292.15** 6038.84** 5253.14* 64.01ns

B×M 8 122.61ns 137.10ns 423.42ns 79.90ns 93.99ns

Error 28 638.49 996.48 302.05 963.15 684.11

Total 44


Mean sum of squares

Sowing-

squaring

Sowing-

flowering

Squaring-

flowering

Sowing-

boll

opening

Flowering-

boll

opening

Replications 2 500.55 456.17 43.13 2706.31 1120.96

Boron (B) 4 16.83ns 2607.46** 2362.37* 5223.49** 646.16ns


B×M 8 5.69ns 154.38ns 156.83ns 167.77ns 101.18ns

Error 28 436.86 529.42 710.22 1154.85 750.99

Total 44


at squaring

MC application

at flowering

Mean (B)

Control 662.64 668.94 647.42 659.67 1 kg B ha

-1 659.44 647.96 659.98 655.79

1.5 kg B ha-1

647.96 646.38 649.85 648.06

2 kg B ha-1

647.55 644.76 647.55 646.62 2.5 kg B ha

-1 652.19 650.48 650.43 651.03

Mean (MC) 653.96 651.70 651.05


at squaring

MC application

at flowering

Mean (B)

Control 608.81 611.55 608.81 609.73 1 kg B ha

-1 610.46 607.60 606.96 608.34

1.5 kg B ha-1

608.81 611.56 608.64 609.67 2 kg B ha

-1 606.58 606.44 606.39 606.47

2.5 kg B ha-1

606.43 608.81 608.14 607.80 Mean (MC) 608.22 609.19 607.79

222

Table 4.239: Influence of mepiquat chloride and boron on thermal time (GDD) taken

from sowing to flowering initiation of cotton




from sowing to flowering initiation of cotton




from squaring to flowering initiation of cotton




from squaring to flowering initiation of cotton




at squaring

MC application

at flowering

Mean (B)

Control 1068.41 1017.37 1071.01 1052.27 A 1 kg B ha

-1 1047.57 1011.12 1043.15 1033.94 AB

1.5 kg B ha-1

1032.58 998.72 1032.41 1021.24 AB 2 kg B ha

-1 1004.10 985.02 1006.37 998.50 B

2.5 kg B ha-1

1020.07 982.50 1018.53 1007.03 B

Mean (MC) 1034.55 A 998.95 B 1034.29 A


at squaring

MC application

at flowering

Mean (B)

Control 977.61 935.31 977.27 963.40 A 1 kg B ha

-1 966.92 922.38 964.07 951.12 AB

1.5 kg B ha-1

951.18 906.91 932.87 930.32 AB 2 kg B ha

-1 935.58 890.94 937.95 921.49 B

2.5 kg B ha-1

956.33 890.94 951.18 932.82 B

Mean (MC) 957.52 A 909.30 B 952.67 A


at squaring

MC application

at flowering

Mean (B)

Control 405.77 348.44 423.59 392.60 A 1 kg B ha

-1 388.13 363.16 383.17 378.15 AB

1.5 kg B ha-1

384.62 352.34 382.56 373.18 ABC 2 kg B ha

-1 356.55 340.26 358.81 351.87 BC

2.5 kg B ha-1

367.88 332.02 368.10 356.00 C

Mean (MC) 380.59 A 347.24 B 383.25 A


at squaring

MC application

at flowering

Mean (B)

Control 368.80 323.76 368.46 353.67 A 1 kg B ha

-1 356.46 314.78 357.11 342.78 AB

1.5 kg B ha-1

342.36 295.35 324.24 320.65 AB 2 kg B ha

-1 329.00 284.51 331.57 315.03 AB

2.5 kg B ha-1

349.90 282.13 343.04 325.02 B Mean (MC) 349.30 A 300.11 B 344.88 A

223


from sowing to boll opening initiation of cotton




from sowing to boll opening initiation of cotton




from flowering to boll opening initiation of cotton



from flowering to boll opening initiation of cotton



at squaring

MC application

at flowering

Mean (B)

Control 1759.19 1723.02 1760.63 1747.61 A 1 kg B ha

-1 1753.09 1719.61 1746.64 1739.78 AB

1.5 kg B ha-1

1735.70 1705.42 1732.77 1724.63 AB 2 kg B ha

-1 1704.66 1683.11 1713.12 1700.30 AB

2.5 kg B ha-1

1725.68 1679.69 1713.77 1706.38 B

Mean (MC) 1735.66 A 1702.17 B 1733.39 A


at squaring

MC application

at flowering

Mean (B)

Control 1670.81 1626.65 1668.15 1655.20 A 1 kg B ha

-1 1650.46 1605.00 1642.35 1632.60 AB

1.5 kg B ha-1

1631.96 1583.41 1629.31 1614.89 AB 2 kg B ha

-1 1612.86 1561.35 1610.07 1594.76 B

2.5 kg B ha-1

1634.45 1556.04 1621.07 1603.85 B

Mean (MC) 1640.11 A 1586.49 B 1634.19 A


at squaring

MC application

at flowering

Mean (B)

Control 690.77 705.65 689.62 695.35 1 kg B ha

-1 705.52 708.49 703.49 705.84

1.5 kg B ha-1

703.12 706.70 700.36 703.39 2 kg B ha

-1 700.55 698.09 706.76 701.80

2.5 kg B ha-1

705.61 697.19 695.25 699.35

Mean (MC) 701.12 703.22 699.09


at squaring

MC application

at flowering

Mean (B)

Control 693.20 691.33 690.88 691.81 1 kg B ha

-1 683.54 682.61 678.28 681.48

1.5 kg B ha-1

680.79 676.49 696.43 684.57 2 kg B ha

-1 677.28 670.41 672.12 673.27

2.5 kg B ha-1

678.12 665.09 669.89 671.03 Mean (MC) 682.59 677.19 681.52

224

matter was decreased at maturity while the reproductive dry matter was increased in

response to both B and mepiquat chloride which further proves that reserve remobilization

was the reason of enhanced earlier physiological cutout. Furthermore, earlier boll retention

also causes earlier maturity through enhanced shift of assimilates to reproductive structures.

Similar results for decreased NAWF and NACB by mepiquat chloride application on cotton

has been reported by Johnson et al. (2006) and Dodds et al. (2010), respectively. However,

no previous report is available for the effect of B on these traits.

Application of B and mepiquat chloride did not affect the days to squaring because

the initiation of squaring is a genetic character and also it is difficult to determine the exact

time of squaring due to its visibility by naked eye as proposed by Saleem et al. (2009);

while, mepiquat chloride was applied after the initiation of squaring stage. However, the

days to flowering, boll opening and mean maturity days were decreased by soil application

of B and mepiquat chloride. Boron is involved in flower production and fruit retention

(Loomis and Durst, 1991; Ahmed et al., 2013) because it is required for pollen tube

development and pollen germination (Lee et al., 2009). Whereas, mepiquat chloride

enhances the earlier flowering and boll retention through decreased vegetative growth and

greater assimilate partitioning to the reproductive structures (Kerby et al., 1996). However,

the earlier boll opening by B and mepiquat chloride was not associated with decrease in

boll maturation period which indicates the earlier boll opening was the result of earlier

flowering and fruit retention; moreover, this earliness was not achieved at the cost of yield.

Soil application of B and foliage applied mepiquat chloride resulted in a decrease

in accumulation of heat units for the commencement of flowering and boll opening. The B

application improved the vegetative growth and caused earlier initiation of reproductive

growth. Whereas, mepiquat chloride caused earlier shift of crop to reproductive growth by

decreasing the vegetative growth. Although both B and mepiquat chloride imposed

differential effect on plant growth but the mechanism of earlier maturity by both was

similar i.e. earlier initiation of reproductive growth. Moreover, this study also indicates that

soil applied B and foliage applied mepiquat chloride decreases the thermal time

requirement to initiate different reproductive growth stages.

The earliness index and production rate index are important indices to measure the

earliness in cotton maturity on the basis of yield. Moreover, these indices indicate the

relationship between yield and earliness which is important from the perspective of

agronomic management. The soil applied B and foliar applied mepiquat chloride enhanced

the earliness index and production rate index. It was observed that B and mepiquat chloride

225

significantly interacted for enhancing the production rate index. It was observed that

enhanced earliness index and production rate index by B and mepiquat chloride were

associated with earlier boll opening and decreased mean maturity days. Furthermore, the

increase in production rate index was the result of decrease in mean maturity days and

enhanced crop yield by the interactive effect of B and mepiquat chloride. This might be

attributed to the boll maturation period which remained unaffected as explained earlier.

Eleyan et al. (2014) reported higher earliness index in response to foliar applied B; while,

Gwathmey and Craig (2003) and Çopur et al. (2010) observed an increase in earliness index

of cotton by mepiquat chloride.

4.2.5. Allometric attributes

4.2.5.1. Dry matter accumulation

4.2.5.1.1. Vegetative dry matter

The pattern of vegetative dry matter showed an increase with time (45-120 DAS)

but later on decreased at maturity (135 DAS), during both years. Maximum vegetative dry

matter was recorded at 120 DAS after which it declined (135 DAS). Soil application of B

exalted the vegetative dry matter, as compared to control during both years. The extent of

influence of B relative to control was increased with increase in time upto 105 DAS;

however, afterwards started declining while leading towards maturity (120-135 DAS).

Mepiquat chloride application lead to differential accumulation of vegetative dry matter.

Application of mepiquat chloride at squaring stage decreased the accumulation of

vegetative dry matter at initial growth stage (45 DAS) and then started increasing with time

(45-120 DAS). However, mepiquat chloride application at flowering stage caused a

decrease in vegetative dry matter at 60-75 DAS and then started increasing afterwards upto

maturity (75-120 DAS) (Figure 4.16).

Soil application of B and mepiquat chloride significantly affected the maximum

vegetative dry matter (120 DAS). However, the interactive effect B and mepiquat chloride

was non-significant regarding vegetative dry matter (Tables 4.247, 4.248). Vegetative dry

matter accumulation was enhanced (14%) by soil application of B, as compared to control

during both years. Maximum vegetative dry matter was recorded by application of 2.5 kg

B ha-1 and it was followed by the effect 1.5 and 2 kg B ha-1 (Tables 4.249, 4.250). On the

other hand, mepiquat chloride decreased the production of vegetative dry matter (9-12%),

as compared to control during both years. It was observed that maximum decrease in

vegetative dry matter was occurred by application of mepiquat chloride at squaring stage

(Tables 4.249, 4.250).

226


chloride and soil applied boron on allometric attributes of cotton (2014)






boron on vegetative dry matter (g m-2) of cotton (2014)



boron on vegetative dry matter (g m-2) of cotton (2015)



Mean sum of squares

Vegetative

dry matter

Reproductive

dry matter

Total dry

matter

Reproductive-

vegetative dry

matter ratio

Replications 2 1509.36 1663.16 1627.97 0.002 Boron (B) 4 3477.30** 14089.87** 27762.12* 0.022* Mepiquat chloride (M) 2 10586.86** 15810.56** 278.93ns 0.518** B×M 8 86.64ns 105.00ns 35.93ns 0.004ns Error 28 468.06 431.20 710.16 0.002 Total 44


Mean sum of squares

Vegetative

dry matter

Reproductive

dry matter

Total dry

matter

Reproductive-

vegetative dry

matter ratio

Replications 2 1338.30 668.33 2240.43 0.012 Boron (B) 4 5671.43** 17173.95** 35016.71** 0.028** Mepiquat chloride (M) 2 9235.03** 10430.58** 909.38ns 0.236** B×M 8 191.27ns 149.65ns 150.04ns 0.004ns Error 28 487.98 588.94 679.43 0.006 Total 44


at squaring

MC application

at flowering

Mean (B)

Control 393.52 352.46 373.55 373.18 C 1 kg B ha

-1 418.44 369.33 391.84 393.20 BC

1.5 kg B ha-1

436.24 381.00 398.10 405.11 AB 2 kg B ha

-1 441.55 389.00 411.67 414.07 AB

2.5 kg B ha-1

460.30 394.23 417.33 423.96 A

Mean (MC) 430.01 A 377.21 C 398.50 B


at squaring

MC application

at flowering

Mean (B)

Control 468.55 435.14 452.19 451.96 C 1 kg B ha

-1 505.73 467.95 471.48 481.72 BC

1.5 kg B ha-1

527.72 481.21 486.25 498.39 AB 2 kg B ha

-1 541.57 488.13 493.63 507.77 AB

2.5 kg B ha-1

551.22 486.00 507.69 514.97 A Mean (MC) 518.96 A 471.69 B 482.25 B

227

Veg

eta

tiv

e d

ry

ma

tter (

g m

-2)

Figure 4.16: Influence of foliar application of mepiquat chloride and soil applied

boron on vegetative dry matter (g m-2) of cotton (a) 2014 (b) 2015

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

500.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135


Control 1 kg B ha-1 1.5 kg B ha-1 2 kg B ha-1 2.5 kg B ha-1 (a)

0.0

100.0

200.0

300.0

400.0

500.0

600.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135


Control 1 kg B ha-1 1.5 kg B ha-1 2 kg B ha-1 2.5 kg B ha-1 (b)

228

4.2.5.1.2. Reproductive dry matter

The temporal pattern of reproductive dry matter exhibited a linear increase in

reproductive dry matter until maturity (45-135 DAS), during both years. Reproductive dry

matter was improved by soil application of B as compared to control and the level of

improvement was increased with time (45-135 DAS). A similar pattern of increase in

reproductive dry matter was noticed either with or without mepiquat chloride application,

although, the increase with mepiquat chloride application was much higher than control.

Moreover, the higher levels of reproductive dry matter accumulation started during 75-90

DAS but the most active accumulation took place during 90-105 DAS (Figures 4.17).

Production of reproductive dry matter was significantly affected by soil applied B

and foliar applied mepiquat chloride but their interaction was non-significant, during both

years (Tables 4.247, 4.248). The accumulation of reproductive dry matter was enhanced

(19-22%) by B with maximum increase occurring by 2 kg B ha-1 during 2014 and 2.5 kg B

ha-1 during 2015. However, during both years 1.5-2.5 kg B ha-1 imposed similar effect on

reproductive dry matter (Tables 4.251, 4.252). Similarly, mepiquat chloride application

enhanced the reproductive dry matter (11-13%), as compared to control and application of

mepiquat chloride at squaring stage was most effective, during both years (Tables 4.251,

4.252).

4.2.5.1.3. Total dry matter

The periodic data of TDM manifested an increase with increase in time upto

maturity, during both years. Soil application of B enhanced the TDM, as compared to

control and the extent of increase was increased with time. The maximum increase in TDM

was recorded between 75-90 DAS and it was followed by 90-105 DAS. Conversely, TDM

accumulation did not differ by the influence of mepiquat chloride; however, the pattern of

TDM accumulation differed by application of mepiquat chloride at different growth stages.

Application of mepiquat chloride at squaring decreased the dry matter accumulation

initially (45 DAS) relative to control; while, mepiquat chloride application at flowering

declined the TDM at 60-75 DAS, during both years (Figure 4.18).

Total dry matter accumulation significantly differed by the effect of soil applied B.

However, foliar application of mepiquat chloride and interactive effect of B and mepiquat

chloride was non-significant during both years (Tables 4.247, 4.248). Accumulation of

TDM was increased by B application (16-17%), as compared to control and maximum

increase was recorded by 2.5 kg B ha-1 while 1.5-2.5 kg B ha-1 was statistically at par

(Tables 4.253, 4.254).

229


boron on reproductive dry matter (g m-2) of cotton (2014)




boron on reproductive dry matter (g m-2) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 455.14 504.56 485.04 481.58 C 1 kg B ha

-1 491.71 565.21 534.29 530.40 B

1.5 kg B ha-1

521.31 584.98 561.66 555.98 AB 2 kg B ha

-1 545.98 608.62 574.53 576.38 A

2.5 kg B ha-1

538.70 613.69 573.98 575.46 A

Mean (MC) 510.57 C 575.41 A 545.90 B


at squaring

MC application

at flowering

Mean (B)

Control 437.62 484.94 460.41 460.99 C 1 kg B ha

-1 479.06 519.33 502.94 500.44 B

1.5 kg B ha-1

513.39 560.08 533.20 535.56 A 2 kg B ha

-1 536.28 590.37 556.91 561.19 A

2.5 kg B ha-1

527.14 602.24 562.32 563.90 A

Mean (MC) 498.70 C 551.39 A 523.16 B

230

Rep

ro

du

cti

ve d

ry

ma

tter (

g m

-2)


boron on reproductive dry matter (g m-2) of cotton (a) 2014 (b) 2015

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

45 60 75 90 105120135 45 60 75 90 105120135 45 60 75 90 105120135


Control 1 kg B ha-1 1.5 kg B ha-1 2.5 kg B ha-1 2 kg B ha-1 (a)

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



231


boron on total dry matter (g m-2) of cotton (2014)


chloride, B: Boron; HSD for B = 36.600.


boron on total dry matter (g m-2) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 843.12 850.74 847.96 847.27 D 1 kg B ha

-1 900.56 915.47 903.40 906.48 C

1.5 kg B ha-1

940.68 950.53 943.03 944.74 B 2 kg B ha

-1 975.48 978.06 970.33 974.62 AB

2.5 kg B ha-1

984.48 985.51 977.03 982.34 A

Mean (MC) 928.86 936.06 928.35


at squaring

MC application

at flowering

Mean (B)

Control 897.92 907.64 901.91 902.49 C 1 kg B ha

-1 975.23 973.46 961.61 970.10 B

1.5 kg B ha-1

1029.04 1011.50 1011.37 1017.30 A 2 kg B ha

-1 1059.87 1044.60 1033.46 1045.98 A

2.5 kg B ha-1

1064.71 1052.70 1040.61 1052.67 A

Mean (MC) 1005.36 997.98 989.79

232

To

tal

dry

ma

tter (

g m

-2)


boron on total dry matter (g m-2) of cotton (a) 2014 (b) 2015

100.0

300.0

500.0

700.0

900.0

1100.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



100.0

300.0

500.0

700.0

900.0

1100.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



233

4.2.5.1.4. Reproductive-vegetative dry matter ratio

The ratio of reproductive to vegetative ratio was significantly affected by soil

application of B and foliar applied mepiquat chloride, however, their interaction was non-

significant, during both years (Tables 4.247, 4.248). It was observed that soil application

of B enhanced the reproductive-vegetative dry matter ratio, as compared to control.

Application of 2 kg B ha-1 produced highest reproductive-vegetative dry matter ratio (1.46

and 1.17 during 2014 and 2015, respectively); however, the effect of 1-2.5 kg B ha-1 was

similar (Tables 4.255, 4.256). Similarly, application of mepiquat chloride imposed a

positive effect in improving the reproductive-vegetative dry matter ratio. The highest

reproductive-vegetative dry matter ratio (1.60 and 1.24 during 2014 and 2015, respectively)

was occurred by application of mepiquat chloride at squaring stage during both years

(Tables 4.255, 4.256).

4.2.5.2. Crop growth rate

The temporal pattern of CGR showed an increase initially and then declined with

further increase in time upto maturity. Crop growth rate was enhanced by soil application

of B, as compared to control. The extent of influence of soil applied B on CGR was

decreased with increase in time from 45 to 135 DAS, during both years. Maximum values

of CGR were obtained between 90-105 DAS with or without mepiquat chloride application,

during both years. Initially, the crop treated with mepiquat chloride at squaring stage

exhibited less CGR (45-60 DAS) and then started increasing with increase in time (upto

90-105 DAS) and afterwards declined (120-135 DAS), as compared to control. On the other

hand, mepiquat chloride application at flowering caused a decrease in CGR between 60-75

DAS, afterwards increased upto 90-105 DAS, and then declined with further increase in

time upto 120-135 DAS (Figures 4.19).

The effect of soil applied B on mean CGR was significant while effect of foliage

applied mepiquat chloride, and interactive effects of B with mepiquat chloride was non-

significant during both years (Tables 4.257, 4.258). The CGR was improved by B

application (17-18%), as compared to control and 2.5 kg B ha-1 caused maximum increase,

during both years. However, the effect of 1.5-2.5 kg B ha-1 imposed a similar effect on

CGR (Tables 4.259, 4.260).

4.2.5.3. Leaf area and leaf area index

Temporal pattern leaf area and LAI showed a sharp increase followed by a decline

at maturity. Boron application increased the leaf area and LAI, as compared to control

during both years and the extent of increase was increased with time. It was observed that

234


boron on reproductive-vegetative dry matter ratio of cotton (2014)




boron on reproductive-vegetative dry matter ratio of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 1.19 1.47 1.34 1.33 B 1 kg B ha

-1 1.21 1.62 1.45 1.43 AB

1.5 kg B ha-1

1.24 1.61 1.47 1.44 AB 2 kg B ha

-1 1.29 1.65 1.45 1.46 A

2.5 kg B ha-1

1.21 1.65 1.42 1.43 A

Mean (MC) 1.23 C 1.60 A 1.43 B


at squaring

MC application

at flowering

Mean (B)

Control 0.95 1.15 1.04 1.05 B 1 kg B ha

-1 0.97 1.16 1.10 1.08 AB

1.5 kg B ha-1

1.00 1.25 1.12 1.12 AB 2 kg B ha

-1 1.03 1.31 1.18 1.17 A

2.5 kg B ha-1

0.99 1.34 1.18 1.17 A

Mean (MC) 0.99 C 1.24 A 1.12 B

235








boron on crop growth rate (g m-2 d-1) of cotton (2014)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for B = 0.3814.


boron on crop growth rate (g m-2 d-1) of cotton (2015)

Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for B = 0.3860.


Mean sum of squares

Crop growth

rate

Leaf area

index

Leaf area

duration

Net

assimilation

rate

Replications 2 0.191 0.003 2.693 0.113 Boron (B) 4 3.011** 0.141** 791.468** 0.033ns Mepiquat chloride (M) 2 0.092ns 0.692** 3604.325** 1.643** B×M 8 0.005ns 0.002ns 3.785ns 0.003ns Error 28 0.077 0.019 72.724 0.112 Total 44


Mean sum of squares

Crop growth

rate

Leaf area

index

Leaf area

duration

Net

assimilation

rate

Replications 2 0.295 0.003 107.74 0.096 Boron (B) 4 3.681** 0.351** 1272.04** 0.083ns Mepiquat chloride (M) 2 0.131ns 0.720** 3714.49** 1.372** B×M 8 0.018ns 0.001ns 42.69ns 0.006ns Error 28 0.079 0.011 50.58 0.113 Total 44


at squaring

MC application

at flowering

Mean (B)

Control 8.12 8.25 8.18 8.19 C 1 kg B ha

-1 8.72 8.93 8.74 8.80 B

1.5 kg B ha-1

9.14 9.31 9.17 9.21 A 2 kg B ha

-1 9.51 9.59 9.45 9.51 A

2.5 kg B ha-1

9.60 9.66 9.50 9.59 A

Mean (MC) 9.02 9.15 9.01


at squaring

MC application

at flowering

Mean (B)

Control 8.56 8.71 8.60 8.62 C 1 kg B ha

-1 9.35 9.40 9.22 9.32 B

1.5 kg B ha-1

9.93 9.80 9.72 9.82 A 2 kg B ha

-1 10.23 10.11 9.95 10.10 A

2.5 kg B ha-1

10.29 10.19 10.00 10.16 A Mean (MC) 9.67 9.64 9.50

236

Cro

p g

ro

wth

ra

te (

g m

-2 d

-1)


boron on crop growth rate (g m-2 d-1) of cotton (a) 2014 (b) 2015

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5



0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5

45-6

0

60-7

5

75-9

0

90-1

05

105

-12

0

120

-13

5



237

Lea

f a

rea

(cm

2)


boron on leaf area (cm2) of cotton (a) 2014 (b) 2015

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



500.00

1500.00

2500.00

3500.00

4500.00

5500.00

6500.00

7500.00

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135

Control MC at squaring MC at floering


238


boron on leaf area index of cotton (2014)




boron on leaf area index of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 3.33 2.95 3.11 3.13 C 1 kg B ha

-1 3.48 3.02 3.21 3.23 BC

1.5 kg B ha-1

3.57 3.10 3.25 3.31 ABC 2 kg B ha

-1 3.62 3.20 3.40 3.40 AB

2.5 kg B ha-1

3.65 3.25 3.40 3.44 A

Mean (MC) 3.53 A 3.10 C 3.27 B


at squaring

MC application

at flowering

Mean (B)

Control 3.51 3.11 3.29 3.30 C 1 kg B ha

-1 3.68 3.24 3.42 3.45 C

1.5 kg B ha-1

3.86 3.43 3.57 3.62 B 2 kg B ha

-1 3.98 3.54 3.69 3.74 AB

2.5 kg B ha-1

4.02 3.56 3.73 3.77 A

Mean (MC) 3.81 A 3.38 C 3.54 B

239

Lea

f a

rea

in

dex


boron on leaf area index of cotton (a) 2014 (b) 2015

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



0.25

0.75

1.25

1.75

2.25

2.75

3.25

3.75

45 60 75 90 105 120 135 45 60 75 90 105 120 135 45 60 75 90 105 120 135



240

maximum increase in leaf area and LAI was recorded between 75-90 DAS either with or

without mepiquat chloride application. However, mepiquat chloride application at squaring

caused a reduction in leaf area and LAI at early growth stage (45 DAS) relative to control,

while, mepiquat chloride application at flowering caused reduction at 60-75 DAS. During

both years, highest leaf area and LAI were recorded at 120 DAS after which it started

declining (135 DAS) (Figures 4.20, 4.21).

Maximum LAI (120 DAS) significantly differed by soil applied B and foliar applied

mepiquat chloride but their interaction was non-significant (Tables 4.257, 4.258). Leaf area

index was increased by soil applied B and 2.5 kg B ha-1 produced highest LAI (3.44 and

3.77 during 2014 and 2015, respectively) while it was followed by 2 kg B ha-1. On the

contrary, mepiquat chloride application reduced the LAI, as compared to control. The

lowest LAI (3.10 and 3.38 during 2014 and 2015, respectively) was recorded by mepiquat

chloride application at squaring stage (Tables 4.261, 4.262).

4.2.5.4. Leaf area duration

Leaf area duration differed significantly by soil applied B and foliar application of

mepiquat chloride; nonetheless, the interactive effect of soil applied B and foliar applied

mepiquat chloride was non-significant, during both years (Tables 4.257, 4.258). Leaf area

duration was enhanced by soil application of B as compared to control. The greatest LAD

(229 and 245 days during 2014 and 2015, respectively) was caused by application of 2.5

kg B ha-1. However, during 2014 similar LAD was produced by application of 1.5 and 2 kg

B ha-1, while, application of 2 kg B ha-1 imposed similar effect, during 2015 (Tables 4.263,

4.264). Conversely, mepiquat chloride application decreased the LAD, as compared to

control during both years. The lowest LAD (204 and 217 days during 2014 and 2015,

respectively) was recorded by application of mepiquat chloride at squaring stage (Tables

4.263, 4.264).

4.2.5.5. Net assimilation rate

A significant effect of mepiquat chloride was noticed on mean NAR while soil

application of B and interaction of B and mepiquat chloride exhibited a non-significant

effect, during both years (Tables 4.257, 4.258). Soil applied B non-significantly improved

the NAR by 2-3% as compared to control. Whereas, NAR was significantly exalted by

application of mepiquat chloride (8-10%), as compared to control. The highest value of

mean NAR was found by application of mepiquat chloride at squaring stage (Tables 4.265,

4.266).

241


boron on leaf area duration (days) of cotton (2014)


chloride, B: HSD for MC = 7.7065, Boron; HSD for B = 11.712.


boron on leaf area duration (days) of cotton (2015)




boron on net assimilation rate (g m-2 d-1) of cotton (2014)


chloride, B: Boron; HSD for MC = 0.3026.


boron on net assimilation rate (g m-2 d-1) of cotton (2015)


chloride, B: Boron; HSD for MC = 0.3033.


at squaring

MC application

at flowering

Mean (B)

Control 220.23 192.33 205.53 206.03 C 1 kg B ha

-1 231.00 199.07 213.43 214.50 BC

1.5 kg B ha-1

237.53 204.70 218.07 220.10 AB 2 kg B ha

-1 242.43 211.10 226.20 226.58 A

2.5 kg B ha-1

244.83 214.00 228.93 229.26 A

Mean (MC) 235.21 A 204.24 C 218.43 B


at squaring

MC application

at flowering

Mean (B)

Control 230.23 201.54 215.67 215.81 D 1 kg B ha

-1 242.12 210.63 224.74 225.83 C

1.5 kg B ha-1

251.13 218.57 232.73 234.14 BC 2 kg B ha

-1 258.31 225.81 240.54 241.55 AB

2.5 kg B ha-1

261.13 229.13 244.92 245.06 A

Mean (MC) 248.58 A 217.14 C 231.72 B


at squaring

MC application

at flowering

Mean (B)

Control 6.74 7.34 6.95 7.01 1 kg B ha

-1 6.80 7.49 7.06 7.11

1.5 kg B ha-1

6.81 7.46 7.09 7.12 2 kg B ha

-1 6.87 7.55 7.08 7.16

2.5 kg B ha-1

6.88 7.52 7.05 7.15

Mean (MC) 6.82 B 7.47 A 7.05 B


at squaring

MC application

at flowering

Mean (B)

Control 7.02 7.56 7.21 7.26 1 kg B ha

-1 7.13 7.79 7.32 7.41

1.5 kg B ha-1

7.26 7.82 7.34 7.47 2 kg B ha

-1 7.25 7.79 7.38 7.47

2.5 kg B ha-1

7.30 7.88 7.34 7.50 Mean (MC) 7.19 B 7.77 A 7.32 B

242

4.2.6. Discussion

Vegetative, reproductive and total dry matter was improved by soil applied B while

foliar application of mepiquat chloride decreased the vegetative dry matter and increased

the reproductive dry matter. However, TDM was not affected by mepiquat chloride

application. The dry matter partitioning was improved by soil applied B and foliar applied

mepiquat chloride as indicated by reproductive-vegetative dry matter ratio. Boron is

involved in the biosynthesis of chlorophyll and increase in rate of photosynthesis which

ultimately leads to increase in dry matter production (Qiong et al., 2002). Similar, results

have been reported for cotton by Rosolem and Costa, (2000), Fontes et al. (2008) and

Ahmed et al. (2011, 2014) that B application enhanced the photosynthesis and CO2 fixation

rate ultimately enhancing the dry matter production. However, in this study mepiquat

chloride decreased the accumulation of vegetative dry matter after its application but started

increasing afterwards with an increase in growth period. However, the reproductive dry

matter was improved right after the initiation of reproductive growth (Gonias et al., 2012;

Mao et al., 2014).

In this study, the dry matter partitioning to reproductive structures was enhanced by

soil applied B and foliar applied mepiquat chloride. Improved dry matter partitioning by B

application might be due to earlier and better boll retention that led to decrease in vegetative

growth with an increase in reproductive growth. Zhao and Oosterhuis (2002) reported

similar results for cotton in response to B. Similarly, enhanced dry matter partitioning to

reproductive structures by mepiquat chloride application was associated with shift in

balance from vegetative to reproductive growth through decrease in vegetative growth. The

results of present study are supported by Zhao and Oosterhuis (200), Gonias et al. (2012)

and Mao et al. (2014) that although the TDM was not improved significantly by mepiquat

chloride but dry matter partitioning was improved significantly.

Similarly, CGR was improved by soil applied B while did not affect by mepiquat

chloride. This was associated with TDM which was enhanced by B but did not affect by

mepiquat chloride application. The LAD was enhanced by soil application of B while

decreased by mepiquat chloride application. Boron application enhanced the leaf area and

LAI which resulted in increased LAD. On the other hand, mepiquat chloride application

imposed an opposite effect on both LAI and LAD. Increase in leaf area by B is attributed

to its positive effect on cell division and cell elongation (Miwa and Fujiwara, 2010b). Zhao

and Oosterhuis (2003) reported that B deficiency caused a reduction in leaf area. However,

mepiquat chloride application decreased the LAD which was associated with lower leaf

243

area and LAI. However, the dry matter accumulation and CGR were least affected by

mepiquat chloride despite of lower LAD. It might be attributed to improved photosynthetic

rate, higher specific leaf area and higher reproductive growth in response to mepiquat

chloride (Zhao and Oosterhuis, 2000). Mepiquat chloride application improved the NAR;

however, soil application of B caused a non-significant improvement in NAR. It might be

attributed to enhanced photosynthetic rate by mepiquat chloride with decreased

assimilatory surface. The improvement in photosynthetic rate might be supported by

enhanced chlorophyll contents and improved light penetration within plant canopy (Gonias

et al., 2012). However, the non-significant improvement in NAR by B application might

also be associated with enhanced photosynthetic rate due to improved leaf area and leaf

chlorophyll contents. However, non-significant improvement explains that the rate of

photosynthesis per unit leaf area was lower.

4.2.7. Boll distribution pattern

Soil application of B and foliar applied mepiquat chloride did not significantly

affect the proportion of first position bolls while significantly affected the second and outer

position bolls. Moreover, the interactive effect of B and mepiquat chloride was non-

significant for proportion of first and second position bolls but significant for outer position

bolls, during both years (Tables 4.267, 4.268).

The percent of second position bolls on sympodial branches among total bolls was

decreased by soil application of B, as compared to control during both years. The least

percent of second position bolls (19 and 20% during 2014 and 2015, respectively) was

observed by application of 2.5 kg B ha-1 but the effect of 1-2.5 kg B ha-1 was statistically

at par during both years (Tables 4.271, 4.272). Similarly, mepiquat chloride decreased the

proportion of second position bolls as compared to control. It was noticed the application

of mepiquat chloride at squaring stage produced lowest proportion of bolls at second

position (19 and 20% during 2014 and 2015, respectively) and it was followed by

application of mepiquat chloride at flowering stage during both years (Tables 4.271, 4.272).

Soil application of B and foliar application of mepiquat chloride exalted the

proportion of bolls at outer sympodial positions, as compared to control during both years.

Furthermore, the interactive effect of soil applied B and foliar mepiquat chloride was more

effective in increasing the outer position bolls at sympodial branches, as compared to their

sole application. Highest outer position bolls (9 and 11% during 2014 and 2015,

respectively) were observed by application of 2.5 kg B ha-1 in combination with mepiquat

chloride application at squaring stage. However, application of 2.5 kg B ha-1 in combination

244


chloride and soil applied boron on boll distribution pattern at sympodial branches of

cotton (2014)



chloride and soil applied boron on boll distribution pattern of cotton (2015)



boron on percent of first position bolls (%) of cotton (2014)



boron on percent of first position bolls (%) of cotton (2015)



Mean sum of squares

1st position

bolls

2nd

position

bolls

Outer

position bolls

Replications 2 2.757 2.991 0.046 Boron (B) 4 3.942ns 10.085* 1.531** Mepiquat chloride (M) 2 6.920ns 18.140** 2.692** B×M 8 0.372ns 0.236ns 0.158* Error 28 2.762 2.533 0.062 Total 44


Mean sum of squares

1st position

bolls

2nd

position

bolls

Outer

position bolls

Replications 2 3.035 3.939 0.077 Boron (B) 4 2.409ns 9.361** 2.283** Mepiquat chloride (M) 2 3.736ns 18.418** 5.658** B×M 8 0.087ns 0.504ns 0.407* Error 28 3.644 2.728 0.127 Total 44


at squaring

MC application

at flowering

Mean (B)

Control 69.44 71.72 71.10 70.75 1 kg B ha

-1 70.67 72.32 71.38 71.46

1.5 kg B ha-1

71.52 72.64 71.98 72.04

2 kg B ha-1

71.96 72.71 72.08 72.25 2.5 kg B ha

-1 71.62 72.79 72.39 72.27

Mean (MC) 71.04 72.44 71.79


at squaring

MC application

at flowering

Mean (B)

Control 68.09 69.51 68.52 68.71 1 kg B ha

-1 68.64 69.55 68.88 69.03

1.5 kg B ha-1

69.03 69.77 69.37 69.39 2 kg B ha

-1 69.29 70.18 69.78 69.75

2.5 kg B ha-1

69.40 70.42 70.11 69.98

Mean (MC) 68.89 69.88 69.33

245


boron on percent of second position bolls (%) of cotton (2014)



boron on percent of second position bolls (%) of cotton (2015)



boron on percent of outer position bolls (%) of cotton (2014)



boron on percent of outer position bolls (%) of cotton (2015)



at squaring

MC application

at flowering

Mean (B)

Control 23.63 20.92 21.57 22.04 A 1 kg B ha

-1 22.07 19.90 20.69 20.88 AB

1.5 kg B ha-1

21.10 19.28 20.33 20.24 AB 2 kg B ha

-1 20.54 18.68 19.79 19.67 B

2.5 kg B ha-1

20.65 18.25 19.29 19.40 B

Mean (MC) 21.60 A 19.41 B 20.33 AB


at squaring

MC application

at flowering

Mean (B)

Control 23.41 21.27 22.62 22.43 A 1 kg B ha

-1 22.43 20.93 21.75 21.70 AB

1.5 kg B ha-1

21.90 20.29 21.03 21.07 AB 2 kg B ha

-1 21.61 19.12 20.15 20.29 AB

2.5 kg B ha-1

21.77 18.43 19.59 19.93 B Mean (MC) 22.22 A 20.01 B 21.03 AB


at squaring

MC application

at flowering

Mean (B)

Control 6.93 g 7.36 efg 7.33 efg 7.21 C 1 kg B ha

-1 7.26 fg 7.78 c-f 7.93 b-f 7.66 B

1.5 kg B ha-1

7.38 d-g 8.08 b-e 7.69 c-f 7.72 B

2 kg B ha-1

7.50 d-g 8.60 ab 8.13 bcd 8.08 A 2.5 kg B ha

-1 7.55 d-g 8.96 a 8.32 abc 8.28 A

Mean (MC) 7.33 C 8.16 A 7.88 B


at squaring

MC application

at flowering

Mean (B)

Control 8.50 g 9.22 c-g 8.86 fg 8.86 D 1 kg B ha

-1 8.93 efg 9.52 c-g 9.36 c-g 9.27 CD

1.5 kg B ha-1

9.08 d-g 9.94 b-e 9.59 c-f 9.54 BC 2 kg B ha

-1 9.10 d-g 10.70 ab 10.08 a-d 9.96 AB

2.5 kg B ha-1

8.83 fg 11.14 a 10.30 abc 10.09 A Mean (MC) 8.89 C 10.11 A 9.64 B

246

with mepiquat chloride application at squaring stage produced statistically results (Tables

4.273, 4.274).

4.2.8. Discussion

Soil application of B and foliar application of mepiquat chloride did not affect the

percent of first position bolls; however, decreased the second position bolls and

significantly interacted for increasing the percent of outer position bolls on sympodial

branches, as compared to control. The decrease in percentage of second position bolls and

increase in outer position bolls indicates that B and mepiquat chloride enhances the fruit

retention even at distal positions on sympodial branches. This indicates the improved boll

retention at distal sympodial positions by the influence of B and mepiquat chloride. Zhao

and Oosterhuis (2002) found that B deficient cotton plants accumulated more non-

structural carbohydrates as compared to floral buds. Moreover, B deficiency decreased the

fruit retention through decreased assimilate translocation from source to sink (Zhao and

Oosterhuis, 2003). On the other hand, mepiquat chloride makes the plant canopy compact

by decreasing the vegetative growth while improving the light penetration and distribution

within plant canopy, improves rate of photosynthesis, makes the photo-assimilates

available for reproductive growth with concomitant increase in boll retention (Zhao and

Oosterhuise, 2000; Gonias et al., 2012; Mao et al., 2015). Gwathmey and Clement (2010)

and Mao et al. (2015) reported that mepiquat chloride increased the boll retention at lower

and middle sympodial branches while decreased at upper branches. Gwathmey and

Clement (2010) further reported that mepiquat chloride application did not affect the first

position bolls.


Application of B and mepiquat chloride as well as their interaction did not impose

a significant effect on plant m-2. However, the number of opened bolls, unopened bolls and

total number of bolls per plants, and average boll weight was significantly affected by

application of B and mepiquat chloride. Furthermore, the interactive effect of soil applied

B and foliar applied mepiquat chloride on number of opened bolls, total number of bolls

per plant and average boll weight during both years, and number of unopened bolls during

2015 was significant but non-significant on number of unopened bolls per plant, during

2014 (Tables 4.275, 4.276).

Number of bolls per plant and average boll weight was improved by soil application

of B and foliar mepiquat chloride alone, as compared to control during both years. Whereas,

the number of bolls and boll weight was improved to a great extent by B when applied in

247


chloride and soil applied boron on yield and related attributes cotton (2014)






boron on number of plants m-2 of cotton (2014)



boron on number of plants m-2 of cotton (2015)



Mean sum of squares

Plants

m-2

No. of

opened

bolls per

plant

No. of

unopened

bolls per

plant

Total No.

of bolls

per plant

Boll

weight

Replications 2 0.020 4.094 0.002 4.262 0.005

Boron (B) 4 0.004ns 16.918** 0.144** 19.963** 0.148**

Mepiquat chloride (M) 2 0.009ns 37.386** 0.179* 38.002** 0.236**

B×M 8 0.003ns 1.730** 0.024ns 1.810* 0.020*

Error 28 0.066 0.525 0.035 0.627 0.008

Total 44


Mean sum of squares

Plants

m-2

No. of

opened

bolls per

plant

No. of

unopened

bolls per

plant

Total No.

of bolls

per plant

Boll

weight

Replications 2 0.493 0.870 0.039 0.541 0.007

Boron (B) 4 0.017ns 10.647** 0.154** 13.077** 0.158**

Mepiquat chloride (M) 2 0.001ns 21.902** 0.087** 22.153** 0.293**

B×M 8 0.012ns 0.964* 0.043* 1.152* 0.030**

Error 28 0.172 0.383 0.015 0.385 0.009

Total 44


at squaring

MC application

at flowering

Mean (B)

Control 5.17 5.23 5.13 5.18 1 kg B ha

-1 5.17 5.15 5.17 5.16

1.5 kg B ha-1

5.10 5.15 5.19 5.15 2 kg B ha

-1 5.17 5.24 5.17 5.20

2.5 kg B ha-1

5.17 5.23 5.17 5.19 Mean (MC) 5.16 5.20 5.17


at squaring

MC application

at flowering

Mean (B)

Control 5.30 5.21 5.22 5.24 1 kg B ha

-1 5.31 5.27 5.39 5.32

1.5 kg B ha-1

5.21 5.18 5.26 5.22 2 kg B ha

-1 5.30 5.33 5.17 5.27

2.5 kg B ha-1

5.27 5.31 5.32 5.30 Mean (MC) 5.28 5.26 5.27

248


boron on number of opened bolls per plant of cotton (2014)



boron on number of opened bolls per plant of cotton (2015)



boron on number of unopened bolls per plant of cotton (2014)



boron on number of unopened bolls per plant of cotton (2015)



at squaring

MC application

at flowering

Mean (B)

Control 19.52 d 21.67 cd 20.67 cd 20.62 C 1 kg B ha

-1 20.67 cd 22.17 c 21.67 cd 21.50 C

1.5 kg B ha-1

21.17 cd 24.47 ab 22.33 bc 22.66 B 2 kg B ha

-1 21.67 cd 25.67 a 22.83 bc 23.39 AB

2.5 kg B ha-1

21.33 cd 26.17 a 24.43 ab 23.98 A

Mean (MC) 20.87 C 24.03 A 22.39 B


at squaring

MC application

at flowering

Mean (B)

Control 17.42 e 19.17 b-e 17.75 de 18.11 C 1 kg B ha

-1 18.00 de 19.42 bcd 18.56 de 18.66 BC

1.5 kg B ha-1

18.42de 20.67 abc 19.08 cde 19.39 B 2 kg B ha

-1 18.75 de 21.58 a 20.75 abc 20.36 A

2.5 kg B ha-1

18.58 de 22.42 a 21.00 ab 20.67 A Mean (MC) 18.23 C 20.65 A 19.43 B


at squaring

MC application

at flowering

Mean (B)

Control 3.48 3.53 3.61 3.54 B 1 kg B ha

-1 3.55 3.62 3.82 3.66 AB

1.5 kg B ha-1

3.68 3.70 3.80 3.73 AB

2 kg B ha-1

3.92 3.70 4.00 3.87 AB 2.5 kg B ha

-1 3.60 3.80 4.00 3.80 A

Mean (MC) 3.65 B 3.67 B 3.85 A


at squaring

MC application

at flowering

Mean (B)

Control 3.05 c 3.12 c 3.17 bc 3.11 C 1 kg B ha

-1 3.15 c 3.18 abc 3.20 abc 3.18 BC

1.5 kg B ha-1

3.25 abc 3.25 abc 3.31 abc 3.27 BC 2 kg B ha

-1 3.55 a 3.25 abc 3.55 a 3.45 A

2.5 kg B ha-1

3.08 c 3.33 abc 3.53 ab 3.32 AB Mean (MC) 3.22 B 3.23 B 3.35 A

249


total number of bolls per plant of cotton (2014)



total number of bolls per plant of cotton (2015)



boll weight (g) of cotton (2014)



boll weight (g) of cotton (2015)


B: Boron; HSD for MC = 0.0839, HSD for B = 0.1275, HSD for MC×B interaction = 0.2807.


at squaring

MC application

at flowering

Mean (B)

Control 23.00 f 25.20 24.28 ef 24.16 C 1 kg B ha

-1 24.22 ef 25.78 cde 25.48 de 25.16 C

1.5 kg B ha-1

24.85 def 28.17 abc 26.13 b-e 26.38 B 2 kg B ha

-1 25.58 de 29.37 a 26.83 bcd 27.26 AB

2.5 kg B ha-1

24.93 def 29.97 a 28.43 ab 27.78 A Mean (MC) 24.52 C 27.70 A 26.23 B


at squaring

MC application

at flowering

Mean (B)

Control 20.47 e 22.28 cde 20.92 de 21.22 C 1 kg B ha

-1 21.15 de 22.60 bcd 21.76 de 21.84 BC

1.5 kg B ha-1

21.66 de 23.91 abc 22.40 cd 22.66 B 2 kg B ha

-1 22.30 cde 24.83 a 24.30 ab 23.81 A

2.5 kg B ha-1

21.67 de 25.75 a 24.53 a 23.98 A

Mean (MC) 21.45 C 23.88 A 22.78 B


at squaring

MC application

at flowering

Mean (B)

Control 2.79 f 2.93 ef 2.88 f 2.87 D 1 kg B ha

-1 2.88 f 3.03 b-f 2.93 def 2.94 CD

1.5 kg B ha-1

2.91 f 3.19 a-e 2.99 c-f 3.03 BC 2 kg B ha

-1 2.94 def 3.28 ab 3.21 a-d 3.14 AB

2.5 kg B ha-1

2.94 def 3.25 abc 3.33 a 3.18 A Mean (MC) 2.89 B 3.14 A 3.07 A


at squaring

MC application

at flowering

Mean (B)

Control 2.84 d 2.99 bcd 2.96 bcd 2.93 D 1 kg B ha

-1 2.92 cd 3.03 bcd 3.03 bcd 3.00 CD

1.5 kg B ha-1

2.98 bcd 3.18 abc 3.07 bcd 3.08 BC 2 kg B ha

-1 2.98 bcd 3.37 a 3.24 ab 3.20 AB

2.5 kg B ha-1

2.92 cd 3.38 a 3.43 a 3.24 A Mean (MC) 2.93 B 3.19 A 3.15 A

250

combination with mepiquat chloride. The highest increase in opened bolls (29-34%) and

total number of bolls per plant (26-30%) was caused by application of 2.5 kg B ha-1 in

combination of mepiquat chloride at squaring stage. However, the effect of 1.5 and 2 kg B

ha-1 in combination with mepiquat chloride at squaring stage as well as 2.5 kg B ha -1 in

combination with mepiquat chloride at flowering stage was statistically similar, during both

years (Tables 4.279, 4.280, 4.283, 4.284). The number of unopened bolls did not improve

by interactive effect of B and mepiquat chloride during 2014 but improved by interaction

during 2015. During 2014, the highest number of unopened bolls were recorded by

application of 2 kg B ha-1 while the effect of 1-2.5 kg B ha-1 was statistically at par.

Likewise, mepiquat chloride application at flowering stage increased the number of

unopened bolls as compared to control. During 2015, the number of unopened bolls were

increased by application of 2 kg B ha-1 alone as well as in combination with mepiquat

chloride at flowering stage. However, the effect of 2.5 kg B ha -1 in combination with

mepiquat chloride application at flowering stage was statistically similar (Tables 4.281,

4.282).

The average boll weight was enhanced by application of B and mepiquat chloride

alone and in combination, as compared to control during both years. The greatest increase

in average boll weight (19-21%) was noticed by application of 2.5 kg B ha-1 in combination

of mepiquat chloride at flowering stage, while, the effect of 2 and 2.5 kg B ha -1 in

combination with mepiquat chloride application at squaring as well as 2 kg B ha -1 in

combination with mepiquat chloride application at flowering stage was statistically similar

(Tables 4.285, 4.286).

Number of seeds per boll, seed index, seed cotton yield, lint yield and cotton seed

yield was significantly affected by soil application of B and foliar applied mepiquat

chloride. The interaction of B and mepiquat chloride for number of seeds per boll and seed

index was non-significant, while, significant for seed cotton yield, lint yield and cotton seed

yield, during both years (Tables 4.287, 4.288).

Soil application of B improved the number of seeds per boll (11%) and seed index

of cotton (8-10%), as compared to control during both years. The highest increase was

noticed by application of 2.5 kg B ha-1 while the effect of 1-2.5 kg B ha-1 was statistically

at par, during both years (Tables 4.289-4.292). Mepiquat chloride application also

improved the number of seeds per boll (10%) and seed index of cotton (9-10%), as

compared to control, with maximum increase occurring by application of mepiquat chloride

at squaring stage, during both years. Nonetheless, the effect of mepiquat chloride

251








boron on number of seeds per boll of cotton (2014)




boron on number of seeds per boll of cotton (2015)




Mean sum of squares

Seeds per boll

Seed index

Seed cotton

yield

Lint yield Cotton seed yield

Replications 2 1.695 0.030 6310 4953.9 1974.8

Boron (B) 4 6.671** 0.307** 358084** 87700.2** 92833.0**

Mepiquat chloride (M) 2 8.107** 0.510** 392630** 69064.3** 132594.5**

B×M 8 0.273ns 0.010ns 31734** 6094.4* 10068.7*

Error 28 1.285 0.057 7536 2506.2 4287.9

Total 44


Mean sum of squares

Seeds per

boll

Seed

index

Seed

cotton

yield

Lint yield Cotton

seed yield

Replications 2 1.905 0.016 3170 832.7 753.2

Boron (B) 4 5.700* 0.407* 238875** 54655.0** 65412.5**

Mepiquat chloride (M) 2 5.800* 0.467* 395098** 63249.0** 142219.7**

B×M 8 0.220ns 0.034ns 19239* 3603.8* 6240.8*

Error 28 1.466 0.106 6071 1385.8 2583.5

Total 44


at squaring

MC application

at flowering

Mean (B)

Control 24.87 26.37 25.45 25.56 B 1 kg B ha

-1 25.48 26.79 26.60 26.29 AB

1.5 kg B ha-1

26.00 27.22 26.60 26.61 AB 2 kg B ha

-1 26.56 28.08 27.57 27.40 A

2.5 kg B ha-1

26.56 28.10 28.45 27.70 A Mean (MC) 25.89 B 27.31 A 26.94 A


at squaring

MC application

at flowering

Mean (B)

Control 24.30 25.96 25.15 25.14 B 1 kg B ha

-1 25.14 26.11 25.81 25.68 AB

1.5 kg B ha-1

25.71 26.68 26.48 26.29 AB 2 kg B ha

-1 26.34 27.38 26.86 26.86 A

2.5 kg B ha-1

26.05 27.38 27.67 27.03 A Mean (MC) 25.51 B 26.70 A 26.39 AB

252


boron on seed index (g) of cotton (2014)



boron on seed index (g) of cotton (2015)



boron on seed cotton yield (kg ha-1) (2014)



boron on seed cotton yield (kg ha-1) (2015)



at squaring

MC application

at flowering

Mean (B)

Control 7.10 7.46 7.26 7.27 B 1 kg B ha

-1 7.27 7.55 7.29 7.37 AB

1.5 kg B ha-1

7.39 7.68 7.51 7.53 AB 2 kg B ha

-1 7.53 7.91 7.61 7.68 A

2.5 kg B ha-1

7.42 7.92 7.71 7.68 A

Mean (MC) 7.34 A 7.71 B 7.47 B


at squaring

MC application

at flowering

Mean (B)

Control 7.01 7.33 7.20 7.18 B 1 kg B ha

-1 7.20 7.36 7.40 7.32 AB

1.5 kg B ha-1

7.32 7.58 7.54 7.48 AB 2 kg B ha

-1 7.47 7.83 7.55 7.62 AB

2.5 kg B ha-1

7.38 8.03 7.70 7.70 A Mean (MC) 7.28 B 7.63 A 7.48 AB


at squaring

MC application

at flowering

Mean (B)

Control 2219 f 2440 def 2384 ef 2348 C 1 kg B ha

-1 2366 ef 2479 c-f 2471 c-f 2439 BC

1.5 kg B ha-1

2423 def 2647 cd 2542 cde 2537 B

2 kg B ha-1

2501 cde 2925 ab 2727 bc 2718 A 2.5 kg B ha

-1 2487 cde 3099 a 2917 ab 2834 A

Mean (MC) 2399 C 2718 A 2608 B


at squaring

MC application

at flowering

Mean (B)

Control 2125 f 2319 ef 2250 ef 2231 C 1 kg B ha

-1 2204 ef 2410 cde 2315 ef 2310 C

1.5 kg B ha-1

2273 ef 2565 bcd 2415 cde 2418 B 2 kg B ha

-1 2329 def 2696 ab 2598 bc 2541 A

2.5 kg B ha-1

2309 ef 2841 a 2738 ab 2629 A Mean (MC) 2248 C 2566 A 2463 B

253


boron on lint yield of cotton (kg ha-1) (2014)


B: Boron; HSD for MC = 45.241, HSD for B = 68.756, HSD for MC×B interaction = 151.43.


boron on lint yield of cotton (kg ha-1) (2015)



boron on cotton seed yield (kg ha-1) (2014)



boron on cotton seed yield (kg ha-1) (2015)



at squaring

MC application

at flowering

Mean (B)

Control 847 e 930 de 916 de 897 C 1 kg B ha

-1 934 de 978 cde 977 cde 963 BC

1.5 kg B ha-1

960 cde 1054 bcd 1019 cd 1011 B 2 kg B ha

-1 1000 cd 1181 ab 1098 bc 1093 A

2.5 kg B ha-1

994 cde 1255 a 1182 ab 1144 A Mean (MC) 947 B 1079 A 1038 A


at squaring

MC application

at flowering

Mean (B)

Control 799 f 874 ef 846 ef 840 C 1 kg B ha

-1 847 ef 924 cde 889 def 887 C

1.5 kg B ha-1

884 def 996 bcd 938 cde 939 B 2 kg B ha

-1 905 def 1056 ab 1024 abc 995 A

2.5 kg B ha-1

900 def 1119 a 1076 ab 1032 A Mean (MC) 867 C 994 A 955 B


at squaring

MC application

at flowering

Mean (B)

Control 1373 d 1510 cd 1469 cd 1450 B 1 kg B ha

-1 1433 cd 1501 cd 1494 cd 1476 B

1.5 kg B ha-1

1463 cd 1593 bc 1523 cd 1526 B 2 kg B ha

-1 1501 cd 1744 ab 1630 bc 1625 A

2.5 kg B ha-1

1493 cd 1844 a 1734 ab 1690 A Mean (MC) 1452 C 1638 A 1570 B


at squaring

MC application

at flowering

Mean (B)

Control 1326 f 1445 c-f 1404 ef 1392 C 1 kg B ha

-1 1357 ef 1486 cde 1426 c-f 1423 BC

1.5 kg B ha-1

1389 ef 1559 bcd 1467 c-f 1472 B 2 kg B ha

-1 1425 c-f 1640 ab 1575 abc 1547 A

2.5 kg B ha-1

1409 def 1722 a 1662 ab 1598 A Mean (MC) 1381 C 1570 A 1507 B

254

application at flowering stage on number of seeds per boll and seed index was statistically

similar, during 2015 (Tables 4.289-4.292).

Seed cotton yield, lint yield and cotton seed yield was improved by soil application

of B and mepiquat chloride alone as well as in combination, as compared to control during

both years. Maximum improvement in seed cotton yield (34-40%), lint yield (40-48%) and

cotton seed yield (30-34%) was noticed by application of 2.5 kg B ha-1 in combination with

mepiquat chloride application at squaring stage. However, the effect of 2.5 kg B ha -1 in

combination with mepiquat chloride application at flowering stage as well as 2 kg B ha -1 in

combination with mepiquat chloride application at squaring stage was statistically similar,

during both years (Tables 4.293-4.298).

4.2.10. Discussion

Yield and related attributes of cotton were improved by soil application of B and

foliar application of mepiquat chloride. Boron and mepiquat chloride significantly

interacted in improving the seed cotton yield, lint yield and cotton seed yield. The enhanced

yield of cotton is attributed to increase in number of opened bolls and boll weight by the

interactive effect of B and mepiquat chloride. Moreover, the increase in boll weight is

attributed to the number of seeds per boll and seed weight (seed index). Although it is

described that the seed cotton yield is a function of number of bolls and bolls weight, but,

basically the yield may be explained in terms of number of seeds and seed weight. It is

known that fiber is produced on seeds, thus the number of seeds and surface area of seed

are the main determinants of yield (Xiao-yu et al., 2016). In our study, it was noticed that

application of B and mepiquat chloride enhanced the number of seeds per boll and seed

weight.

The increase in number of seeds per boll and number of bolls per plant by B might

be attributed to the role of B in reproductive growth mainly in the pollen development,

pollen germination and pollen tube growth (Lee et al., 2009) thus affecting the seed set and

boll retention (Ahmed et al., 2013). Whereas, improved boll weight may be attributed to

involvement of B in sugar synthesis, metabolism and translocation (Mengel and Kirkby,

2001; Barker and Pilbeam, 2007). Mepiquat chloride enhanced the number of bolls and boll

weight which may be explained by the fact that it enhances the dry matter partitioning to

the developing reproductive structure through enhanced photosynthesis and assimilate

partitioning (Zhao and Oosterhuise, 2000; Gwathmey and Clement, 2010). Furthermore, in

present study it was observed that the number of bolls were increased more by foliar

application of mepiquat chloride at squaring stage while boll weight was enhanced more

255

by mepiquat chloride at flowering stage. As explained earlier, this might be due to the fact

that mepiquat chloride application at squaring produced a higher boll load due to which

demand for photo-assimilates might have not been fulfilled resulting in decreased boll

weight. Further, it was observed that the number of seeds per boll were higher in response

to mepiquat chloride application at flowering stage which contributed to enhanced boll

weight.

4.2.11. Fiber quality attributes

Ginning out turn and micronaire was significantly affected by soil applied B during

both years while fiber maturity was significantly affected during 2014 only. Whereas, the

effect of mepiquat chloride and interaction between B and mepiquat chloride was non-

significant for these traits during both years. Furthermore, fiber length, fiber strength and

fiber uniformity ratio did not differ significantly by the influence of soil applied B, foliar

applied mepiquat chloride as well as their interaction, during both years (Tables 4.299,

4.300).

Soil application of B improved the ginning out turn, as compared to control during

both years. The highest ginning out turn (40.3 and 39.2% during 2014 and 2015,

respectively) was recorded by application of 2.5 kg B ha-1, while, the effect of 1-2.5 kg B

ha-1 was statistically at par during both years (Tables 4.301, 4.302). Micronaire was

improved by soil applied B, as compared to control during both years. The micronaire was

improve most by application of 2.5 kg B ha-1, and it was followed by 1-2.5 kg B ha-1 (Tables

4.305, 4.306). Soil applied B improved the fiber maturity, during 2014. The greatest

improvement in fiber maturity was occurred by application of 2.5 kg B ha-1, while, the

effect of 1-2.5 kg B ha-1 was similar (Tables 4.311, 4.312).

4.2.12. Discussion

Soil application of B improved some of the fiber quality attributes. It was observed

that B application improved the ginning out turn, micronaire and fiber maturity while fiber

length, fiber uniformity and fiber strength was not affected. This might be due to the fact

that fiber quality is a genetic character and influenced by environment; however, nutrition

has little effect. Besides, it was noticed that B application rate had little effect on these fiber

quality traits which indicates that nutrients are required by plants in very minute quantity

for improving the fiber quality and any additional application than required impose very

slight effect. The improved ginning out turn by B application might be due to involvement

of B in cell wall structure and strengthening (Miwa and Fujiwara, 2010a; Bellaloui et al.,

2015); while, fiber is the elongation of cells (Ritchie et al., 2007). Similar, response of fiber

256


chloride and soil applied boron on fiber quality of cotton (2014)



chloride and soil applied boron on fiber quality of cotton (2015)



boron on ginning out turn (%) of cotton (2014)




boron on ginning out turn (%) of cotton (2015)




Mean sum of squares

Ginning out turn

Fiber length

Micron-aire

Fiber strength

Fiber uniformity

ratio

Fiber maturity

Replications 2 3.880 0.175 0.020 0.938 6.121 0.622

Boron (B) 4 6.422* 0.329ns 0.069* 0.149ns 0.297ns 7.411*

Mepiquat chloride (M) 2 0.396ns 0.047ns 0.001ns 0.021ns 0.434ns 2.156ns

B×M 8 0.062ns 0.027ns 0.001ns 0.004ns 0.021ns 0.128ns

Error 28 2.076 0.822 0.019 0.552 2.535 2.122

Total 44


Mean sum of squares

Ginning

out turn

Fiber

length

Micron

-aire

Fiber

strength

Fiber

uniformity

ratio

Fiber

maturity

Replications 2 0.084 0.607 0.0016 0.371 0.685 9.867

Boron (B) 4 3.867** 0.189ns 0.0448* 0.159ns 1.191ns 0.756ns

Mepiquat chloride (M) 2 0.107ns 0.207ns 0.0029ns 0.081ns 0.163ns 0.467ns

B×M 8 0.075ns 0.014ns 0.0009ns 0.009ns 0.012ns 0.106ns

Error 28 0.737 0.758 0.0149 0.691 3.227 1.724

Total 44


at squaring

MC application

at flowering

Mean (B)

Control 38.16 38.11 38.42 38.23 B 1 kg B ha

-1 39.44 39.43 39.55 39.47 AB

1.5 kg B ha-1

39.65 39.84 40.08 39.86 AB

2 kg B ha-1

39.95 40.39 40.23 40.19 AB 2.5 kg B ha

-1 40.00 40.51 40.52 40.34 A

Mean (MC) 39.44 39.65 39.76


at squaring

MC application

at flowering

Mean (B)

Control 37.60 37.67 37.62 37.63 B 1 kg B ha

-1 38.45 38.35 38.38 38.39 AB

1.5 kg B ha-1

38.90 38.83 38.84 38.85 A 2 kg B ha

-1 38.82 39.17 39.41 39.13 A

2.5 kg B ha-1

38.99 39.40 39.30 39.23 A Mean (MC) 38.55 38.68 38.71

257


boron on fiber length (mm) of cotton (2014)



boron on fiber length (mm) of cotton (2015)



boron on micronaire (µg inch-1) of cotton (2014)




boron on micronaire (µg inch-1) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 26.83 27.03 27.00 26.96 1 kg B ha

-1 26.83 27.10 27.13 27.02

1.5 kg B ha-1

27.10 27.27 27.27 27.21 2 kg B ha

-1 27.40 27.33 27.33 27.36

2.5 kg B ha-1

27.43 27.33 27.37 27.38

Mean (MC) 27.12 27.21 27.22


at squaring

MC application

at flowering

Mean (B)

Control 26.50 26.70 26.63 26.61 1 kg B ha

-1 26.63 26.77 26.73 26.71

1.5 kg B ha-1

26.70 26.77 26.87 26.78 2 kg B ha

-1 26.73 27.00 27.00 26.91

2.5 kg B ha-1

26.73 27.07 27.10 26.97 Mean (MC) 26.66 26.86 26.87


at squaring

MC application

at flowering

Mean (B)

Control 4.43 4.47 4.47 4.46 B 1 kg B ha

-1 4.47 4.50 4.47 4.48 AB

1.5 kg B ha-1

4.53 4.57 4.53 4.54 AB 2 kg B ha

-1 4.63 4.60 4.63 4.62 AB

2.5 kg B ha-1

4.67 4.63 4.67 4.66 A Mean (MC) 4.55 4.55 4.55


at squaring

MC application

at flowering

Mean (B)

Control 4.37 4.37 4.40 4.38 B 1 kg B ha

-1 4.40 4.43 4.47 4.43 AB

1.5 kg B ha-1

4.47 4.47 4.47 4.47 AB 2 kg B ha

-1 4.53 4.50 4.53 4.52 AB

2.5 kg B ha-1

4.53 4.57 4.57 4.56 A Mean (MC) 4.46 4.47 4.49

258


boron on fiber strength (g tex-1) of cotton (2014)



boron on fiber strength (g tex-1) of cotton (2015)



boron on fiber uniformity ratio (%) of cotton (2014)



boron on fiber uniformity ratio (%) of cotton (2015)



at squaring

MC application

at flowering

Mean (B)

Control 23.57 23.67 23.73 23.66 1 kg B ha

-1 23.70 23.73 23.80 23.74

1.5 kg B ha-1

23.83 23.83 23.87 23.84 2 kg B ha

-1 23.90 23.93 23.90 23.91

2.5 kg B ha-1

23.93 24.00 24.00 23.98

Mean (MC) 23.79 23.83 23.86


at squaring

MC application

at flowering

Mean (B)

Control 23.07 23.23 23.13 23.14 1 kg B ha

-1 23.13 23.27 23.17 23.19

1.5 kg B ha-1

23.20 23.33 23.30 23.28 2 kg B ha

-1 23.30 23.40 23.43 23.38

2.5 kg B ha-1

23.33 23.47 23.60 23.47 Mean (MC) 23.21 23.34 23.33


at squaring

MC application

at flowering

Mean (B)

Control 51.97 52.13 52.27 52.12 1 kg B ha

-1 52.00 52.20 52.27 52.16

1.5 kg B ha-1

52.07 52.20 52.27 52.18 2 kg B ha

-1 52.20 52.47 52.57 52.41

2.5 kg B ha-1

52.20 52.73 52.67 52.53 Mean (MC) 52.09 52.35 52.41


at squaring

MC application

at flowering

Mean (B)

Control 51.33 51.60 51.53 51.49 1 kg B ha

-1 51.60 51.67 51.60 51.62

1.5 kg B ha-1

51.93 52.10 52.20 52.08 2 kg B ha

-1 52.00 52.13 52.23 52.12

2.5 kg B ha-1

52.20 52.43 52.43 52.36 Mean (MC) 51.81 51.99 52.00

259


boron on fiber maturity (%) of cotton (2014)




boron on fiber maturity (%) of cotton (2015)



at squaring

MC application

at flowering

Mean (B)

Control 81.00 81.67 82.00 81.56 B 1 kg B ha

-1 82.33 82.33 83.00 82.56 AB

1.5 kg B ha-1

82.67 83.00 83.33 83.00 AB 2 kg B ha

-1 83.67 83.33 84.00 83.67 A

2.5 kg B ha-1

83.33 83.67 84.33 83.78 A

Mean (MC) 82.60 82.80 83.33


at squaring

MC application

at flowering

Mean (B)

Control 81.33 82.00 81.67 81.67 1 kg B ha

-1 82.00 82.00 81.67 81.89

1.5 kg B ha-1

82.00 82.33 82.00 82.11 2 kg B ha

-1 82.33 82.33 82.33 82.33

2.5 kg B ha-1

82.00 82.67 82.33 82.33

Mean (MC) 81.93 82.27 82.00

260

quality to B has been reported in literature. For example, Zhao and Oosterhuis (2002) and

Ahmed et al. (2013) reported a non-significant effect of soil applied B on fiber quality

while Ahmad et al. (2009a) and Sabino et al. (1996) reported a significant improvement in

fiber quality. On the other hand, mepiquat chloride application at either stage did not

impose a significant effect on fiber quality traits. As explained earlier, mepiquat chloride

has no direct effect on fiber quality; it may improve fiber quality by increasing the number

of first position bolls. Similar to present study results, Wilson et al. (2007) reported that

mepiquat chloride imposed a minor increase in fiber length while there was no significant

effect on fiber strength, fiber uniformity and micronaire. Ren et al. (2013) reported that

mepiquat chloride application decreased lint percentage while increased the fiber length

and strength of cotton.

4.2.13. Photosynthetic pigments

Chlorophyll a, b, total chlorophyll and carotenoids contents were significantly

affected by soil application of B, foliar applied mepiquat chloride and their interaction

during both years. However, chlorophyll a/b ratio was not affected significantly by soil

application of B, foliar applied mepiquat chloride and their interaction during 2014.

However, during 2015, the chlorophyll a/b ratio was significantly differed by application

of B and mepiquat chloride but their interaction was non-significant (Tables 4.313, 4.314).

An improvement in the biosynthesis of chlorophyll a, b and total chlorophyll was

occurred by soil application of B and foliar application of mepiquat chloride alone as well

as in combination, as compared to control during both years. However, the effect of B and

mepiquat chloride in combination was much higher, as compared to their sole application.

The biosynthesis of chlorophyll a (44-51%), chlorophyll b (54-63%) and total chlorophyll

(49-52%) was enhanced most by 2.5 kg B ha-1 when applied in combination with mepiquat

chloride application at squaring, during both years. However, the effect of 2.5 kg B ha -1 in

combination with mepiquat chloride application at flowering as well as the effect of 2 kg

B ha-1 when applied in combination with mepiquat chloride application at squaring stage

was statistically similar (Tables 4.315-4.320). Conversely, application of B and mepiquat

chloride decreased the chlorophyll a/b ratio, as compared to control during 2015. Least

chlorophyll a/b ratio (2.86) was recorded by application of application of 2.5 kg B ha-1

while the effect of 1.5-2.5 kg B ha-1 was statistically at par. On the other hand, minimum

chlorophyll a/b ratio (2.90) was observed by application of mepiquat chloride at squaring

stage ad it was followed by application of mepiquat chloride at flowering stage (Tables

4.321, 4.322). Similar to chlorophyll contents, the carotenoids were enhanced by soil

261


chloride and soil applied boron on photosynthetic pigments of cotton (2014)



chloride and soil applied boron on photosynthetic pigments of cotton (2015)



boron on chlorophyll a content (mg g-1 FW) of cotton (2014)





boron on chlorophyll a content (mg g-1 FW) of cotton (2015)






Replications 2 0.0017 0.0002 0.0027 0.0191 0.00001 Boron (B) 4 0.0159** 0.0038** 0.0347** 0.0160ns 0.00159**

Mepiquat chloride (M) 2 0.0529** 0.0098** 0.1075** 0.0092ns 0.00698** B×M 8 0.0023** 0.0004** 0.0040** 0.0109ns 0.00029** Error 28 0.0005 0.0001 0.0006 0.0117 0.00006 Total 44



Replications 2 0.0011 0.0001 0.0020 0.0047 0.0001 Boron (B) 4 0.0375** 0.0073** 0.0778** 0.0527** 0.0044** Mepiquat chloride (M) 2 0.0689** 0.0136** 0.1471** 0.1105** 0.0094** B×M 8 0.0026** 0.0004** 0.0049** 0.0043ns 0.0006**

Error 28 0.0006 0.0001 0.0009 0.0076 0.0001 Total 44


at squaring

MC application

at flowering

Mean (B)

Control 0.45 i 0.53 d-h 0.52 e-h 0.50 C 1 kg B ha

-1 0.48 hi 0.56 d-g 0.53 d-h 0.52 BC

1.5 kg B ha-1

0.49 ghi 0.56 d-g 0.57 cde 0.54 B 2 kg B ha

-1 0.50 f-i 0.65 ab 0.59 bcd 0.58 A

2.5 kg B ha-1

0.49 ghi 0.69 a 0.64 abc 0.61 A Mean (MC) 0.49 C 0.60 A 0.57 B


at squaring

MC application

at flowering

Mean (B)

Control 0.61 f 0.69 def 0.69 def 0.66 C 1 kg B ha

-1 0.65 ef 0.74 cd 0.69 def 0.69 C

1.5 kg B ha-1

0.68 def 0.81 bc 0.82 abc 0.77 B 2 kg B ha

-1 0.70 de 0.87 ab 0.81 bc 0.79 AB

2.5 kg B ha-1

0.70 de 0.89 a 0.83 ab 0.81 A

Mean (MC) 0.67 C 0.80 A 0.77 B

262


chlorophyll b content (mg g-1

FW) of cotton (2014)



chlorophyll b content (mg g-1




total chlorophyll content (mg g-1




total chlorophyll content (mg g-1





at squaring

MC application

at flowering

Mean (B)

Control 0.17 g 0.21 def 0.20 def 0.19 C

1 kg B ha-1

0.19 fg 0.22 cd 0.21 def 0.20 BC 1.5 kg B ha

-1 0.19 fg 0.22 cd 0.22 cd 0.21 B

2 kg B ha-1

0.20 def 0.26 ab 0.24 bc 0.23 A 2.5 kg B ha

-1 0.20 def 0.27 a 0.27 a 0.24 A

Mean (MC) 0.19 C 0.24 A 0.22 B


at squaring

MC application

at flowering

Mean (B)

Control 0.20 h 0.23 efg 0.22 fg 0.22 D

1 kg B ha-1

0.21 gh 0.25 de 0.23 fg 0.23 C 1.5 kg B ha

-1 0.23 efg 0.28 cd 0.29 bc 0.26 B

2 kg B ha-1

0.24 ef 0.31 ab 0.29 bc 0.27 A 2.5 kg B ha

-1 0.23 efg 0.32 a 0.30 abc 0.28 A

Mean (MC) 0.22 C 0.28 A 0.26 B


at squaring

MC application

at flowering

Mean (B)

Control 0.62 g 0.74 de 0.72 def 0.69 D 1 kg B ha

-1 0.66 fg 0.78 cd 0.74 de 0.73 CD

1.5 kg B ha-1

0.69 efg 0.79 cd 0.79 cd 0.75 C

2 kg B ha-1

0.70 efg 0.90 ab 0.83 bc 0.81 B 2.5 kg B ha

-1 0.69 ef 0.95 a 0.90 ab 0.85 A

Mean (MC) 0.67 C 0.83 A 0.80 B


at squaring

MC application

at flowering

Mean (B)

Control 0.81 e 0.92 cd 0.91 cd 0.88 D

1 kg B ha-1

0.86 de 1.00 c 0.92 cd 0.92 C 1.5 kg B ha

-1 0.91 d 1.09 b 1.10 b 1.03 B

2 kg B ha-1

0.93 cd 1.17 ab 1.10 b 1.07 AB 2.5 kg B ha

-1 0.94 cd 1.21 a 1.13 ab 1.09 A

Mean (MC) 0.89 C 1.08 A 1.03 B

263


chlorophyll a/b ratio of cotton (2014)

Mepiquat chloride, B: Boron.


chlorophyll a/b ratio of cotton (2015)



carotenoids content (mg g-1




carotenoids content (mg g-1




at squaring

MC application

at flowering

Mean (B)

Control 2.64 2.55 2.61 2.60

1 kg B ha-1

2.58 2.54 2.57 2.56 1.5 kg B ha

-1 2.62 2.54 2.63 2.60

2 kg B ha-1

2.53 2.51 2.51 2.52 2.5 kg B ha

-1 2.56 2.60 2.38 2.51

Mean (MC) 2.59 2.55 2.54


at squaring

MC application

at flowering

Mean (B)

Control 3.15 2.97 3.07 3.06 A 1 kg B ha

-1 3.11 2.93 2.96 3.00 AB

1.5 kg B ha-1

3.02 2.91 2.87 2.93 BC 2 kg B ha

-1 2.98 2.89 2.86 2.91 BC

2.5 kg B ha-1

3.01 2.79 2.80 2.86 C Mean (MC) 3.05 A 2.90 B 2.91 B


at squaring

MC application

at flowering

Mean (B)

Control 0.15 g 0.17 efg 0.17 d-g 0.16 D 1 kg B ha

-1 0.15 g 0.19 b-e 0.18 c-f 0.18 C

1.5 kg B ha-1

0.16 fg 0.20 a-d 0.18 c-f 0.18 BC 2 kg B ha

-1 0.16 fg 0.21 ab 0.21 ab 0.19 AB

2.5 kg B ha-1

0.16 fg 0.22 a 0.21 ab 0.20 A Mean (MC) 0.16 B 0.20 A 0.19 A


at squaring

MC application

at flowering

Mean (B)


-1 0.18 d 0.21 cd 0.20 cd 0.20 C

1.5 kg B ha-1

0.19 cd 0.22 bc 0.22 bc 0.21 BC 2 kg B ha

-1 0.19 cd 0.25 ab 0.22 bc 0.22 B

2.5 kg B ha-1

0.19 cd 0.27 a 0.27 a 0.25 A

Mean (MC) 0.19 B 0.23 A 0.22 A

264

application of B and foliage applied mepiquat chloride, alone as well as in combination, as

compared to control during both years. Highest increase in carotenoids contents (46-55%)

was observed by 2.5 kg B ha-1 when applied in combination with mepiquat chloride

application at squaring, as compared to control. However, the effect of 2.5 kg B ha -1 in

combination with mepiquat chloride application at flowering as well as the effect of 2 kg

B ha-1 when applied in combination with mepiquat chloride application at squaring stage

produced similar results (Tables 4.323, 4.324).

4.2.14. Discussion

Photosynthetic pigments in cotton leaves were substantially improved by

interactive effect of soil applied B and foliar application of mepiquat chloride. Chlorophyll

a, b, total chlorophyll and carotenoids contents were increased linearly by an increase in B

application rate. Mepiquat chloride application exaggerated the biosynthesis of

photosynthetic pigments at each level of B. Enhanced biosynthesis of photosynthetic

pigments by soil application of B on cotton might be due to better protection of thylakoid

and chloroplast membranes because of its role in functioning and integrity of plasma

membranes (Huang et al., 2005). Moreover, B deficiency results in the deterioration of

chloroplast structure and reduces the chlorophyll contents (Hao et al., 2012). Boron

deficiency also leads to the accumulation of starch and sugars in leaves with a decrease in

photosynthesis (Han et al., 2008). Similar to this study results, several other researchers

have reported exaggeration in leaf photosynthetic pigments by B application such as pine

(Apostol and Zwiazek, 2004), Dittrichia viscosa (Stavrianakou et al., 2006) and orange

(Sheng et al., 2009). Enhanced biosynthesis of chlorophyll and carotenoids contents by

mepiquat chloride application might be due to greater specific leaf weight as reported by

Reddy et al. (1996). Gliožeris et al. (2007) reported that application of some plant

regulators including growth retardant chlomequat chloride (CCC), paclobutrazol and

daminozide enhanced the chlorophyll a, b and carotenoids contents in viola × wittrockiana

‘Wesel Ice’. Similarly, Rosolem et al. (2013) reported an improved chlorophyll contents in

cotton in response to mepiquat chloride. Present study results showed that higher

chlorophyll a, b, total chlorophyll and carotenoid contents were noticed by mepiquat

chloride application at squaring than flowering stage which might be due to lesser plant

growth by mepiquat chloride application at squaring stage or due to higher specific leaf

weight.

265

4.2.15. Tissue nutrient contents

4.2.15.1. Macronutrients

The contents of N, P and K in leaf and seed tissues of cotton were significantly

affected by soil application of B and mepiquat chloride while their interaction was non-

significant, during both years (Tables 4.325, 4.326).

Nitrogen contents in leaf and seed tissues were enhanced by soil application of B,

as compared to control during both years. Application of 2.5 kg B ha-1 caused maximum

increase in N contents in leaf (8-12%) and seed tissues (5%). However, the effect of 1-2.5

kg B ha-1 on N content in both leaf and cotton seed tissues was similar (Tables 4.327-4.330).

Likewise, mepiquat chloride imposed a positive effect on leaf and seed N contents, as

compared to control during both years. Highest N contents in leaves (9-11%) and seed of

cotton (4%) were recorded by mepiquat chloride application at squaring stage. However,

application of mepiquat chloride at flowering produced statistically similar results for leaf

N during 2014 and seed N contents during both years (Tables 4.327-4.330).

Soil application of B enhanced the P contents in leaf and seed tissues, as compared

to control during both years. Maximum increase in P contents in leaves (17-20%) and seed

(13-19%) was observed by application of 2.5 kg B ha -1 and it was followed by 2.5 kg B ha-

1 (Tables 4.331-4.334). Mepiquat chloride application improved the leaf and seed P

contents, as compared to control during both years. Highest P contents in leaf (10-13%)

and seed tissues of cotton (13-19%) were recorded by mepiquat chloride application at

squaring stage, while, the effect of mepiquat chloride application at flowering produced

similar results for leaf P contents, during 2014 (Tables 4.331-4.334).

Potassium contents in leaf and seed tissues were enhanced by soil application of B,

as compared to control during both years. Highest K contents in leaf (12-13%) and seed

tissues (10-13%) were noticed by application of 2.5 kg B ha-1. However, 1.5-2.5 kg B ha-1

produced similar results for K contents in leaf and cotton seed tissues (Tables 4.335-4.338).

Similarly, mepiquat chloride enhanced the K contents, as compared to control during both

years. The greatest increase in K contents in leaves (10-12%) and seed tissues (9-14%) of

cotton were recorded by mepiquat chloride application at squaring stage. However,

application of mepiquat chloride at flowering produced similar results for leaf K contents


4.2.15.2. Micronutrients

Soil application of B and foliar applied mepiquat chloride significantly affected the

B, Zn, Mn and Fe contents in leaf and seed tissues of cotton. Moreover, the interaction

266


chloride and soil applied boron on contents of macronutrients in leaves and seed

tissues of cotton (2014)



chloride and soil applied boron on contents of macronutrients in leaves and seed

tissues of cotton (2015)



boron on leaf nitrogen content (mg g-1 DW) of cotton (2014)




boron on leaf nitrogen content (mg g-1 DW) of cotton (2015)




Mean sum of squares



Replications 2 14.337 20.714 0.0062 0.0101 10.017 11.640

Boron (B) 4 4.510* 4.578* 0.0780** 0.3098** 13.237** 9.347**

Mepiquat chloride (M) 2 20.842** 6.271* 0.1141** 0.3548** 29.773** 28.233**

B×M 8 0.118ns 0.024ns 0.0033ns 0.0086ns 1.093ns 0.686ns

Error 28 1.310 1.293 0.0049 0.0162 1.822 1.298

Total 44


Mean sum of squares



Replications 2 15.178 6.247 0.065 0.003 13.080 5.158

Boron (B) 4 10.830** 4.277* 0.118** 0.584** 10.754** 5.439**

Mepiquat chloride (M) 2 19.198** 6.209* 0.162** 0.510** 19.953** 10.570**

B×M 8 0.140ns 0.071ns 0.010ns 0.026ns 1.064ns 0.290ns

Error 28 0.990 1.259 0.006 0.022 1.799 0.742

Total 44


at squaring

MC application

at flowering

Mean (B)

Control 19.36 21.65 21.39 20.80 B 1 kg B ha

-1 20.11 22.17 21.74 21.34 AB

1.5 kg B ha-1

20.60 22.56 21.93 21.69 AB 2 kg B ha

-1 20.96 23.45 22.66 22.36 AB

2.5 kg B ha-1

20.98 23.35 23.18 22.50 A Mean (MC) 20.40 B 22.63 A 22.18 A


at squaring

MC application

at flowering

Mean (B)

Control 22.34 24.64 23.26 23.41 C 1 kg B ha

-1 23.26 25.62 24.15 24.34 BC

1.5 kg B ha-1

23.95 25.66 24.88 24.83 B 2 kg B ha

-1 24.40 26.77 25.73 25.63 AB

2.5 kg B ha-1

25.09 27.65 25.92 26.22 A Mean (MC) 23.81 C 26.07 A 24.79 B

267


boron on seed nitrogen content (mg g-1 DW) of cotton (2014)




boron on seed nitrogen content (mg g-1 DW) of cotton (2015)




boron on leaf phosphorus content (mg g-1 DW) of cotton (2014)




boron on leaf phosphorus content (mg g-1 DW) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 31.41 32.83 32.17 32.14 B 1 kg B ha

-1 32.31 33.38 32.98 32.89 AB

1.5 kg B ha-1

32.62 33.93 33.52 33.36 AB 2 kg B ha

-1 33.13 34.35 33.76 33.75 A

2.5 kg B ha-1

33.13 34.52 34.04 33.90 A

Mean (MC) 32.52 B 33.80 A 33.29 AB


at squaring

MC application

at flowering

Mean (B)

Control 31.08 32.59 31.55 31.74 B 1 kg B ha

-1 31.44 32.77 32.08 32.10 AB

1.5 kg B ha-1

31.78 33.17 32.59 32.51 AB 2 kg B ha

-1 32.67 33.57 33.27 33.17 AB

2.5 kg B ha-1

32.75 34.06 33.27 33.36 A

Mean (MC) 31.94 B 33.23 A 32.55 AB


at squaring

MC application

at flowering

Mean (B)

Control 1.27 1.40 1.31 1.33 C 1 kg B ha

-1 1.27 1.42 1.35 1.35 C

1.5 kg B ha-1

1.32 1.47 1.47 1.42 BC 2 kg B ha

-1 1.37 1.58 1.50 1.48 AB

2.5 kg B ha-1

1.42 1.62 1.61 1.55 A

Mean (MC) 1.33 B 1.50 A 1.45 A


at squaring

MC application

at flowering

Mean (B)

Control 1.30 1.38 1.37 1.35 C 1 kg B ha

-1 1.27 1.38 1.40 1.35 C

1.5 kg B ha-1

1.32 1.57 1.50 1.46 B 2 kg B ha

-1 1.40 1.67 1.50 1.52 AB

2.5 kg B ha-1

1.47 1.78 1.60 1.62 A Mean (MC) 1.35 C 1.56 A 1.47 B

268


boron on seed phosphorus content (mg g-1 DW) of cotton (2014)




boron on seed phosphorus content (mg g-1 DW) of cotton (2015)




boron on leaf potassium content (mg g-1 DW) of cotton (2014)




boron on leaf potassium content (mg g-1 DW) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 3.45 3.88 3.64 3.66 C 1 kg B ha

-1 3.72 4.00 4.00 3.90 B

1.5 kg B ha-1

3.82 4.07 3.99 3.96 AB 2 kg B ha

-1 3.97 4.22 4.09 4.09 A

2.5 kg B ha-1

3.97 4.29 4.12 4.13 A

Mean (MC) 3.79 C 4.09 A 3.97 B


at squaring

MC application

at flowering

Mean (B)

Control 3.27 3.52 3.37 3.39 C 1 kg B ha

-1 3.36 3.72 3.46 3.52 BC

1.5 kg B ha-1

3.53 3.80 3.63 3.65 B 2 kg B ha

-1 3.63 3.98 3.98 3.86 A

2.5 kg B ha-1

3.72 4.33 4.00 4.02 A

Mean (MC) 3.50 C 3.87 A 3.69 B


at squaring

MC application

at flowering

Mean (B)

Control 21.61 23.90 22.76 22.76 C 1 kg B ha

-1 22.46 24.16 23.99 23.54 BC

1.5 kg B ha-1

22.88 25.86 24.12 24.29 ABC 2 kg B ha

-1 23.54 26.19 26.25 25.33 AB

2.5 kg B ha-1

23.43 27.69 25.87 25.66 A

Mean (MC) 22.79 B 25.56 A 24.60 A


at squaring

MC application

at flowering

Mean (B)

Control 20.50 22.77 22.17 21.81 B 1 kg B ha

-1 21.32 22.30 22.39 22.00 B

1.5 kg B ha-1

21.84 24.43 22.57 22.95 AB 2 kg B ha

-1 22.37 25.02 23.46 23.61 A

2.5 kg B ha-1

22.49 25.35 25.40 24.41 A Mean (MC) 21.70 B 23.97 A 23.20 A

269


boron on seed potassium content (mg g-1 DW) of cotton (2014)




boron on seed potassium content (mg g-1 DW) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 18.65 20.88 19.83 19.79 C 1 kg B ha

-1 19.27 20.82 20.78 20.29 BC

1.5 kg B ha-1

19.76 22.40 21.61 21.25 ABC 2 kg B ha

-1 19.84 23.24 21.60 21.56 AB

2.5 kg B ha-1

20.40 24.17 22.48 22.35 A

Mean (MC) 19.58 C 22.30 A 21.26 B


at squaring

MC application

at flowering

Mean (B)

Control 17.67 19.24 18.63 18.51 C 1 kg B ha

-1 18.36 19.74 19.30 19.13 BC

1.5 kg B ha-1

18.76 20.05 19.72 19.51 ABC 2 kg B ha

-1 19.26 21.19 20.09 20.18 AB

2.5 kg B ha-1

19.57 21.77 19.95 20.43 A

Mean (MC) 18.72 C 20.40 A 19.54 B

270

between soil applied B and foliar applied mepiquat chloride was significant for leaf and

seed B contents while non-significant for Zn, Mn and Fe contents in leaf and seed tissues,


Boron contents in leaf and seed tissues of cotton was enhanced by application of

soil applied B and foliar applied mepiquat chloride as well as their combination, as

compared to control. However, the combination of B and mepiquat chloride exhibited

greater improvement. Application of 2.5 kg B ha -1 in combination with mepiquat chloride

application at squaring stage enhanced the leaf (52-58%) and seed B contents (49-59%)

most. Application of 2 kg B ha-1 in combination with mepiquat chloride application at

squaring stage as well as 2.5 kg B ha-1 in combination with mepiquat chloride application

at flowering stage was statistically similar (Tables 4.341-4.344).

Zinc and Fe contents were enhanced in leaf and cotton seed tissues by application

of B, as compared to control during both years. Maximum increase in Zn contents in cotton

leaves (9-13%) and seed (9-12%), as well as Fe contents in leaf (9-12%) and seed tissues

(9-14%) was noticed by soil application of 2.5 kg B ha-1. However, the effect of 1-2.5 kg

B ha-1 was statistically at par for leaf and seed Zn and Fe contents (Tables 4.345-4.348,

4.353-4.356). Similarly, mepiquat chloride application enhanced the contents of Zn

contents in leaves (7-8%) and cotton seed (8%), and Fe contents in leaves (4-5%) and cotton

seed (5-7%), as compared to control during both years. Mepiquat chloride application at

squaring stage enhanced the Zn and Fe contents most, while, mepiquat chloride application

at flowering stage produced statistically similar results for these micronutrients, during both

years (Tables 4.345-4.348, 4.353-4.356).

The contents of Mn in leaf and cotton seed tissues were reduced by application of

B, as compared to control during both years. Maximum decrease in Mn contents in cotton

leaves (11-14%) and seed (11-12%) were caused by soil application of 2.5 kg B ha-1.

However, the effect of 1-2.5 kg B ha-1 was statistically at par (Tables 4.349-4.352). Similar

effect of mepiquat chloride was observed for Mn contents in leaf (5-9%) and seed tissues

(6-9%), during both years. Mepiquat chloride application at squaring stage caused

maximum decrease in Mn contents, while, mepiquat chloride application at flowering stage

produced similar results (Tables 4.349-4.352).

4.2.16. Discussion

Uptake and translocation of macronutrients viz. N, P and K in cotton leaf and seed

tissues was increased by soil application of B and foliar applied mepiquat chloride.

Moreover, the increase in N, P and K contents was proportional to the B application rate.

271

Table 4.339: Analysis of variance for influence of foliar application of mepiquat chloride and soil applied boron on contents of



Table 4.340: Analysis of variance for influence of foliar application of mepiquat chloride and soil applied boron on contents of




Mean sum of squares



Replications 2 0.520 1.169 0.824 6.216 4.703 2.695 9.071 100.659 Boron (B) 4 169.556** 241.146** 14.891** 35.572** 85.288** 10.765** 628.485** 771.832** Mepiquat chloride (M) 2 115.619** 140.715** 28.609** 43.922** 93.747** 15.009** 263.441** 319.678** B×M 8 5.754* 14.307** 0.428ns 1.883ns 8.946ns 0.380ns 42.178ns 47.655ns Error 28 2.221 3.075 2.830 4.570 4.432 1.004 28.734 42.803 Total 44


Mean sum of squares



Replications 2 7.379 6.475 16.944 27.235 2.457 0.035 518.03 475.88 Boron (B) 4 146.491** 127.955** 28.811** 21.692* 45.608** 7.973** 376.22** 385.06** Mepiquat chloride (M) 2 97.118** 107.564** 32.820** 37.355** 28.395** 5.582** 211.58* 503.73**

B×M 8 5.361* 3.990* 1.086ns 0.334ns 2.372ns 0.287ns 22.82ns 16.21ns Error 28 1.946 1.487 4.361 5.700 4.593 0.916 38.81 48.95 Total 44

272


leaf boron content (µg g-1


Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for MC = 1.3468, HSD for B = 2.0468, HSD for MC×B interaction= 4.5080.


leaf boron content (µg g-1




seed boron content (µg g-1


Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B: Boron; HSD for MC = 1.5846, HSD for B = 2.4082, HSD for MC×B interaction= 5.3040.


seed boron content (µg g-1




at squaring

MC application

at flowering

Mean (B)

Control 31.93 g 35.77 fg 35.61 fg 34.43 D

1 kg B ha-1

36.70 ef 38.80 ef 36.89 ef 37.46 C 1.5 kg B ha

-1 37.86 ef 44.73 abc 40.90 cde 41.16 B

2 kg B ha-1

39.19 def 46.54 ab 43.43 bcd 43.05 B 2.5 kg B ha

-1 41.00 cde 48.43 a 46.35 ab 45.26 A

Mean (MC) 37.34 C 42.85 A 40.64 B


at squaring

MC application

at flowering

Mean (B)

Control 28.28 h 32.43 fgh 30.47 gh 30.39 E 1 kg B ha

-1 32.63 fg 34.53 efg 33.46 efg 33.54 D

1.5 kg B ha-1

34.92 def 39.00 bcd 35.48 def 36.46 C 2 kg B ha

-1 35.76 def 42.43 ab 37.53 cde 38.57 B

2.5 kg B ha-1

36.47 c-f 44.82 a 40.39 bc 40.56 A Mean (MC) 33.61 C 38.64 A 35.46 B


at squaring

MC application

at flowering

Mean (B)

Control 35.23 g 39.05 efg 37.91 fg 37.40 C 1 kg B ha

-1 40.03 d-g 42.94 c-f 40.77 def 41.25 B

1.5 kg B ha-1

41.91 def 44.56 cd 42.72 c-f 43.06 B 2 kg B ha

-1 43.52 cde 52.53 ab 47.93 bc 47.99 A

2.5 kg B ha-1

43.86 cde 56.10 a 50.82 ab 50.26 A Mean (MC) 40.91 C 47.04 A 44.03 B


at squaring

MC application

at flowering

Mean (B)

Control 31.16 h 35.68 fg 33.15 gh 33.33D 1 kg B ha

-1 34.79 fgh 37.11ef 35.93 fg 35.94 C

1.5 kg B ha-1

36.14 fg 41.23 bcd 39.83 cde 39.07 B

2 kg B ha-1

37.49 ef 44.02 ab 41.83 bcd 41.11 A 2.5 kg B ha

-1 38.24 def 46.37 a 43.07 abc 42.56 A

Mean (MC) 35.56 C 40.88 A 38.76 B

273


boron on leaf zinc content (µg g-1 DW) of cotton (2014)




boron on leaf zinc content (µg g-1 DW) of cotton (2015)




boron on seed zinc content (µg g-1 DW) of cotton (2014)




boron on seed zinc content (µg g-1 DW) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 35.16 38.13 36.90 36.73 B 1 kg B ha

-1 37.20 39.11 39.14 38.48 AB

1.5 kg B ha-1

37.19 40.34 39.29 38.94 AB 2 kg B ha

-1 38.45 41.04 39.42 39.64 A

2.5 kg B ha-1

38.43 41.51 40.16 40.03 A

Mean (MC) 37.29 B 40.02 A 38.98 A


at squaring

MC application

at flowering

Mean (B)

Control 32.87 35.64 35.18 34.56 C 1 kg B ha

-1 33.98 36.73 35.47 35.39 BC

1.5 kg B ha-1

35.34 37.49 36.54 36.46 ABC 2 kg B ha

-1 36.35 38.60 38.57 37.84 AB

2.5 kg B ha-1

36.28 40.25 40.39 38.97 A

Mean (MC) 34.96 B 37.74 A 37.23 A


at squaring

MC application

at flowering

Mean (B)

Control 41.71 45.81 43.67 43.73 C 1 kg B ha

-1 43.43 45.76 45.80 45.00 BC

1.5 kg B ha-1

44.97 47.41 45.88 46.09 ABC 2 kg B ha

-1 45.71 48.23 47.56 47.17 AB

2.5 kg B ha-1

45.90 51.47 49.33 48.90 A

Mean (MC) 44.34 B 47.73 A 46.45 A


at squaring

MC application

at flowering

Mean (B)

Control 38.37 41.61 40.47 40.15 B 1 kg B ha

-1 39.67 42.89 41.41 41.32 AB

1.5 kg B ha-1

41.27 43.77 42.28 42.44 AB 2 kg B ha

-1 41.47 45.01 43.97 43.48 A

2.5 kg B ha-1

42.43 45.69 43.67 43.93 A Mean (MC) 40.64 B 43.79 A 42.36 AB

274


boron on leaf manganese content (µg g-1 DW) of cotton (2014)




boron on leaf manganese content (µg g-1 DW) of cotton (2015)




boron on seed manganese content (µg g-1 DW) of cotton (2014)




boron on seed manganese content (µg g-1 DW) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 56.19 54.97 56.05 55.74 A 1 kg B ha

-1 55.72 51.82 55.07 54.20 A

1.5 kg B ha-1

54.29 48.43 51.20 51.31 B 2 kg B ha

-1 53.98 48.14 48.74 50.29 BC

2.5 kg B ha-1

53.13 45.52 45.47 48.04 C

Mean (MC) 54.66 A 49.78 B 51.31 B


at squaring

MC application

at flowering

Mean (B)

Control 54.63 54.04 53.02 53.90 A 1 kg B ha

-1 52.50 51.21 50.91 51.54 AB

1.5 kg B ha-1

52.35 49.38 50.72 50.81 BC 2 kg B ha

-1 51.01 47.05 48.99 49.02 BC

2.5 kg B ha-1

50.62 46.19 47.64 48.15 C

Mean (MC) 52.22 A 49.57 B 50.25 B


at squaring

MC application

at flowering

Mean (B)

Control 24.37 23.04 23.97 23.79 A 1 kg B ha

-1 23.82 21.88 22.78 22.83 AB

1.5 kg B ha-1

23.18 21.16 22.49 22.28 BC 2 kg B ha

-1 22.70 20.20 21.96 21.62 BC

2.5 kg B ha-1

22.30 20.09 20.47 20.95 C

Mean (MC) 23.27 A 21.27 C 22.33 B


at squaring

MC application

at flowering

Mean (B)

Control 21.73 20.94 20.90 21.19 A 1 kg B ha

-1 21.42 20.17 20.65 20.75 AB

1.5 kg B ha-1

20.43 19.41 19.59 19.81 BC 2 kg B ha

-1 20.09 18.33 19.75 19.39 C

2.5 kg B ha-1

19.43 18.16 19.19 18.92 C Mean (MC) 20.62 A 19.40 B 20.02 AB

275


boron on leaf iron content (µg g-1 DW) of cotton (2014)




boron on leaf iron content (µg g-1 DW) of cotton (2015)




boron on seed iron content (µg g-1 DW) of cotton (2014)




boron on seed iron content (µg g-1 DW) of cotton (2015)




at squaring

MC application

at flowering

Mean (B)

Control 163.29 165.11 166.17 164.86 B 1 kg B ha

-1 168.76 174.27 168.57 170.53 B

1.5 kg B ha-1

174.05 180.24 181.30 178.53 A 2 kg B ha

-1 174.79 188.05 179.50 180.78 A

2.5 kg B ha-1

176.13 189.66 191.60 185.80 A

Mean (MC) 171.41 B 179.47 A 177.43 A


at squaring

MC application

at flowering

Mean (B)

Control 165.25 168.86 166.43 166.85 C 1 kg B ha

-1 169.64 171.49 170.49 170.54 BC

1.5 kg B ha-1

170.05 179.03 178.63 175.90 AB 2 kg B ha

-1 174.54 185.94 178.94 179.81 A

2.5 kg B ha-1

175.44 186.19 186.02 182.55 A

Mean (MC) 170.98 B 178.30 A 176.10 AB


at squaring

MC application

at flowering

Mean (B)

Control 172.57 173.56 174.78 173.64 D 1 kg B ha

-1 175.76 180.68 181.19 179.21 CD

1.5 kg B ha-1

180.87 187.79 184.19 184.28 BC 2 kg B ha

-1 184.37 197.32 188.43 190.04 AB

2.5 kg B ha-1

187.63 207.98 196.68 197.43 A

Mean (MC) 180.24 B 189.47 A 185.06 AB


at squaring

MC application

at flowering

Mean (B)

Control 166.57 175.09 170.39 170.68 C 1 kg B ha

-1 169.84 178.66 178.59 175.69 BC

1.5 kg B ha-1

175.65 185.71 180.32 180.56 AB 2 kg B ha

-1 178.26 190.76 185.35 184.79 AB

2.5 kg B ha-1

178.03 195.96 185.71 186.57 A Mean (MC) 173.67 B 185.24 A 180.07 A

276

It has been observed that B has positive interaction with N and improves its uptake and

translocation by positively regulating the activation of enzymes involved in N metabolism

and/or by promoting and controlling the entrance of substrate through cellular membranes

to interior of cell (Ruiz et al., 1998). Likewise, B has synergistic effect on P and that might

be due to its positive effect on P assimilation (Ahmed et al., 2011). Similarly, the positive

effect of B on K is due to hyperpolarization of cell membranes consequently leading to

enhanced K accumulation in cells (Schon et al., 1990). Similar results were reported by

Ahmed et al. (2011) that soil application of B enhanced the uptake and translocation of N,

P and K in cotton leaf, seed and lint. Foliar application of mepiquat chloride improved the

N, P and K contents in leaves and seed of cotton. Mepiquat chloride application enhances

root growth which seems the reason of enhanced nutrient uptake (Duan et al., 2004).

Whereas, root growth of plants is highly important in acquiring nutrients from soil

(Newman and Andrews, 1973). Mepiquat chloride enhances the conversion of amino acids

into protein that results in enhanced uptake and translocation of N (Wang and Chen, 1984).

Moreover, mepiquat chloride application enhances the photo-assimilation and assimilate

partitioning that demands for high amount of nutrients (Zhao and Oosterhuis, 2000;

Gwathmey and Clement, 2010). Khan et al. (2005) concluded that PGR application

enhanced the N uptake and recovery efficiency through improved plant growth and CO2

exchange rate. Similar increase in N and K by cotton in response to mepiquat chloride was

reported by Sawan et al. (2009). Likewise, Yang et al. (2014) observed an increase in K

uptake, recovery and use efficiency in cotton by mepiquat chloride application.

Similar to macronutrients the contents of micronutrients (B, Zn and Fe) was

increased while Mn was decreased by soil application of B and mepiquat chloride. The

contents of B, Zn and Fe was increased with increase in B dosage while response of Mn

was vice versa. It was observed that soil application of B and foliar applied mepiquat

chloride significantly interacted in improving the leaf and seed B contents. Improved leaf

and seed B contents by soil application of B might be attributed to enhanced soil available

B pool that resulted in enhanced uptake and translocation of B. Mepiquat chloride

application further improved the uptake and translocation of B which may be due to its

positive interaction with B in enhancing the root growth as well as assimilate partitioning

(Duan et al., 2004; Zhao and Oosterhuis, 2000); moreover, mepiquat chloride has been

found to increase the transpiration rate (Zhao and Oosterhuis, 2000) which may be the

reason of enhanced B uptake and translocation because B is transported from roots to other

plant parts through transpiration stream (Mengel and Kirkby, 2001).

277

On the other hand, exalted uptake and translocation of Zn and Fe might be due to

their positive interaction with B. However, the Mn uptake and translocation was decreased

by soil application of B which may be due to its antagonistic effect with B (Mouhtaridou

et al., 2004). Similarly, Ahmed et al. (2011) reported that soil application of B improved

the concentration of B, Zn and Fe, while, decreased Mn contents in cotton leaf and seed

tissues. Present study results showed that mepiquat chloride application enhanced the

concentration of micronutrients except Mn in leaf and seed tissues of cotton. The

improvement of micronutrients viz. Zn and Fe by mepiquat chloride might be due to same

reason as for macronutrients. However, lesser uptake and translocation of Mn by mepiquat

chloride might be due to enhanced uptake of B which restricted it due to their antagonistic

effect on each other.

4.2.17. Cotton seed nutritional quality

Cotton seed oil, protein and ash contents, and oil and protein yield was significantly

affected by soil application of B and foliar application of mepiquat chloride. Nonetheless,

the interactive effect of B and mepiquat chloride was non-significant for oil, protein and

ash contents while significant for oil and protein yield, during both years (Tables 4.357,

4.358).

Application of B considerably improved the cotton seed nutritional quality, as

compared to control during both years. Maximum increase in cotton seed oil (4-6%),

protein (5%) and ash contents (6-7%) was caused by 2.5 kg B ha-1. However, the effect of

1-2.5 kg B ha-1 was at par except for ash contents during 2014 in which the effect of 1.5-

2.5 kg B ha-1 was similar (Tables 4.359-4.364). Likewise, mepiquat chloride improved the

cotton seed nutritional quality, as compared to control during both years. Application of

mepiquat chloride at squaring exalted the oil (4-5%), protein (4%) and ash contents (6-8%)

and it was followed by mepiquat chloride application at flowering stage. However, during

2015 the effect of mepiquat chloride application at both growth stages differed regarding

seed ash content (Tables 4.359-4.364). Maximum increase in cotton seed oil yield (46-

47%) and protein yield (42-47%) was caused by application of 2.5 kg B ha-1 in combination

with mepiquat chloride application at squaring during both years. However, the effect of 2

kg B ha-1 in combination with mepiquat chloride application at squaring and 2.5 kg B ha-1

in combination with mepiquat chloride application at flowering was similar (Tables 4.365-

4.368).

278


chloride and soil applied boron on cotton seed nutritional quality (2014)



chloride and soil applied boron on cotton seed nutritional quality (2015)



boron on cotton seed oil content (%) (2014)




boron on cotton seed oil content (%) (2015)




Mean sum of squares

Oil

content

Protein

content

Ash

content

Oil yield Protein

yield

Replications 2 0.001 4.482 0.006 69.82 1342.43

Boron (B) 4 1.302* 1.785* 0.130** 6167.29** 6926.90** Mepiquat chloride (M) 2 1.921* 2.448* 0.451** 8964.60** 9951.45** B×M 8 0.063ns 0.009ns 0.014ns 489.59* 511.24** Error 28 0.396 0.564 0.021 154.68 157.48 Total 44


Mean sum of squares

Oil

content

Protein

content

Ash

content

Oil yield Protein

yield

Replications 2 0.031 2.431 0.243 25.07 313.93 Boron (B) 4 1.767* 1.670* 0.130** 4757.86** 5109.61**

Mepiquat chloride (M) 2 3.490** 2.419* 0.231** 10080.10** 9907.49** B×M 8 0.087ns 0.027ns 0.011ns 282.57* 279.91* Error 28 0.569 0.492 0.027 114.14 106.42 Total 44


at squaring

MC application

at flowering

Mean (B)

Control 19.11 20.15 19.84 19.70 B 1 kg B ha

-1 19.67 20.19 19.97 19.94 AB

1.5 kg B ha-1

19.97 20.59 20.02 20.19 AB

2 kg B ha-1

20.28 20.93 20.41 20.54 AB 2.5 kg B ha

-1 20.23 20.93 20.53 20.56 A

Mean (MC) 19.85 B 20.56 A 20.15 AB


at squaring

MC application

at flowering

Mean (B)

Control 18.13 19.24 18.87 18.75 B 1 kg B ha

-1 18.82 19.88 18.87 19.19 AB

1.5 kg B ha-1

19.14 19.89 19.56 19.53 AB 2 kg B ha

-1 19.35 20.14 19.56 19.68 AB

2.5 kg B ha-1

19.38 20.44 19.79 19.87 A Mean (MC) 18.96 B 19.92 A 19.33 AB

279


boron on cotton seed protein content (%) (2014)




boron on cotton seed protein content (%) (2015)




boron on cotton seed ash content (%) (2014)




boron on cotton seed ash content (%) (2015)




at squaring

MC application

at flowering

Mean (B)

Control 19.63 20.52 20.11 20.08 B 1 kg B ha

-1 20.19 20.86 20.61 20.56 AB

1.5 kg B ha-1

20.38 21.21 20.95 20.85 AB 2 kg B ha

-1 20.71 21.46 21.10 21.09 AB

2.5 kg B ha-1

20.71 21.58 21.27 21.18 A

Mean (MC) 20.32 B 21.12 A 20.81 AB


at squaring

MC application

at flowering

Mean (B)

Control 19.42 20.37 19.72 19.84 B 1 kg B ha

-1 19.65 20.48 20.05 20.06 AB

1.5 kg B ha-1

19.86 20.73 20.37 20.32 AB 2 kg B ha

-1 20.42 20.98 20.79 20.73 AB

2.5 kg B ha-1

20.47 21.29 20.79 20.85 A

Mean (MC) 19.97 B 20.77 A 20.34 AB


at squaring

MC application

at flowering

Mean (B)

Control 3.97 4.31 4.39 4.22 C 1 kg B ha

-1 4.05 4.42 4.43 4.30 BC

1.5 kg B ha-1

4.21 4.52 4.42 4.38 ABC 2 kg B ha

-1 4.30 4.56 4.48 4.45 AB

2.5 kg B ha-1

4.36 4.70 4.52 4.53 A

Mean (MC) 4.18 B 4.50 A 4.45 A


at squaring

MC application

at flowering

Mean (B)

Control 4.16 4.55 4.40 4.37 B 1 kg B ha

-1 4.36 4.59 4.47 4.47 AB

1.5 kg B ha-1

4.55 4.69 4.55 4.60 AB 2 kg B ha

-1 4.55 4.80 4.55 4.63 A

2.5 kg B ha-1

4.58 4.78 4.60 4.66 A Mean (MC) 4.44 B 4.68 A 4.52 B

280


cotton seed oil yield (kg ha-1

) (2014)




cotton seed oil yield (kg ha-1

) (2015)




cotton seed protein yield (kg ha-1

) (2014)




cotton seed protein yield (kg ha-1

) (2015)




at squaring

MC application

at flowering

Mean (B)

Control 262 f 304 cde 291 def 286 C

1 kg B ha-1

282 ef 303 cde 298 c-f 294 BC 1.5 kg B ha

-1 292 def 328 bcd 305 cde 308 B

2 kg B ha-1

304 cde 365 ab 333 bc 334 A 2.5 kg B ha

-1 302 cde 386 a 356 ab 348 A

Mean (MC) 288 C 337 A 317 B


at squaring

MC application

at flowering

Mean (B)

Control 240 g 278 def 265 efg 261 C 1 kg B ha

-1 255 fg 295 cde 269 efg 273 C

1.5 kg B ha-1

266 efg 312 bc 289 cde 289 B 2 kg B ha

-1 276 ef 330 ab 308 bcd 305 A

2.5 kg B ha-1

273 efg 352 a 329 ab 318 A Mean (MC) 262 C 313 A 292 B


at squaring

MC application

at flowering

Mean (B)

Control 270 g 310 def 295 fg 291 C 1 kg B ha

-1 289 fg 313 def 308 ef 303 BC

1.5 kg B ha-1

298 fg 337 cde 319 def 318 B

2 kg B ha-1

311 def 374 ab 344 bcd 343 A 2.5 kg B ha

-1 309 def 398 a 369 abc 359 A

Mean (MC) 295 C 346 A 327 B


at squaring

MC application

at flowering

Mean (B)

Control 258 g 294 def 277 efg 276 C 1 kg B ha

-1 267 fg 304 cde 286 efg 285 C

1.5 kg B ha-1

276 efg 325 bcd 301 cde 301 B

2 kg B ha-1

291 ef 344 ab 327 bc 321 A 2.5 kg B ha

-1 288 efg 367 a 346 ab 333 A

Mean (MC) 276 C 327 A 307 B

281

4.2.18. Discussion

Cotton seed nutritional quality (oil, protein and ash contents) was improved by soil

application of B and mepiquat chloride. It has been observed that B nutrition improves the

rate of photosynthesis and uptake of N by plants ultimately improving the C and N

metabolism (Ahmed et al., 2014). In present study, the enhanced protein content by soil

applied B is attributed to enhanced N uptake and translocation; while, higher oil and ash

contents are attributed to enhanced biosynthesis of photosynthetic pigments which might

have increased the photosynthetic rate. Similar results were reported by Ahmed et al.

(2013) that soil application of B improved the cotton seed protein and oil contents. The

improved cotton seed protein content in response to mepiquat chloride application is

attributed to its role in protein synthesis through enhanced conversion of amino acids in to

protein (Wang and Chen, 1984). The higher oil and ash contents might be attributed to

improved photo-assimilation and assimilate translocation of photosynthates from source to

sink (Zhao and Oosterhuis, 2000; Gwathmey and Clement, 2010). Similar, results were

reported by Sawan et al. (2001) and Sawan et al. (2007). Cotton seed oil and protein yield

was substantially improved by synergistic effect of soil application of B and foliage applied

mepiquat chloride. The results of this study showed that there was an increase in protein

and oil contents, as well as cotton seed yield by B and mepiquat chloride application which

resultantly produced higher oil and protein yield. Similarly, Sawan et al. (2001) reported

higher oil and protein yield by application of N, Zn and mepiquat chloride.


The NUE of B for cotton was improved by soil B fertilization and foliar application

of mepiquat chloride relative to their respective controls. It was observed that application

of mepiquat chloride at both growth stages enhanced the NUE of B. However, highest NUE

of B (1.27 and 1.23 during 2014 and 2015, respectively) was recorded by application of 2.5

kg B ha-1 in combination with mepiquat chloride application at squaring stage and it was

followed by application of 2.5 kg B ha-1 in combination with mepiquat chloride application

at squaring stage, during both years (Figure 4.22).

4.2.20. Critical value of boron

The relationship between near maximum seed cotton yield (95% of highest yield)

and B contents in leaves for the years 2014 and 2015 showed that critical value of B for

cotton was increased by application of mepiquat chloride, as compared to control. It was

observed that the critical value of B with control (no mepiquat chloride), mepiquat chloride

282

application at squaring stage and mepiquat chloride application at flowering stage was 34,

46 and 43 µg B g-1 dry leaves, respectively (Figure 4.23).

4.2.21. Boron fertilizer requirement

The relationship between relative seed cotton yield (95% of highest yield) and B

contents in leaves for the years 2014 and 2015 showed that requirement of cotton crop for

B fertilization was increased by application of mepiquat chloride. The fertilizer requirement

of cotton with control (no mepiquat chloride), mepiquat chloride application at squaring

stage and mepiquat chloride application at flowering stage was 1, 2.1 and 2.1 kg B ha -1,

respectively (Figure 4.24).

4.2.22. Discussion

Nutrient use efficiency of B was enhanced by soil applied B; however, mepiquat

chloride application at both stages caused greater improvement in NUE as compared to sole

application of B. The increased NUE of B by mepiquat chloride is attributed to improved

B uptake from soil nutrient pool. Mepiquat chloride application improves the ability of

plants for greater uptake of nutrient from soil through enhanced root growth (Duan et al.,

2004). Khan et al. (2005) suggested that plant growth regulators improves the nutrient

uptake and use efficiency through enhanced plant growth, leaf CO2 exchange rate, and

nutrient uptake and accumulation. Moreover, López-Bellido et al. (2010) described that

PGRs such as trinexapac-ethyl and paclobutrazol could increase soil organic C, thus

increasing soil’s cation exchange capacity or its capability to hold on and supply the

essential nutrients and accelerate the decomposition of minerals in soil over time, making

the nutrients available in minerals for uptake by plants. Thus mepiquat chloride would have

affected the ability of plants to enhance the B uptake from indigenous and soil applied B

pool that led to improvement in yield formation resulting in enhanced NUE.

Mepiquat chloride application increased the critical value of B, as compared to

control. As explained earlier that critical value of B may vary with varying the factors that

affect the B uptake and translocation such as water, soil type, soil texture and soil reaction,

organic matter, crop and soil management practices, plant spacing, microbial activity, plant

species, cultivar etc. (Sims and Johnson, 1991; Nabi et al., 2006; Barker and Pilbeam,

2007). Therefore, variation in critical value of B by mepiquat chloride can be explained on

the basis of modification in uptake and utilization ability of plants. There was less yield

formation as compared to B uptake and accumulation which lead to increase in critical

value of B. Soil application of B increased the plant available B in soil while mepiquat

chloride application might have increased the root growth (Duan et al., 2004) and

283

Nu

trie

nt

use

eff

icie

ncy

Figure 4.22: Influence of foliar applied mepiquat chloride and soil applied boron on

nutrient use efficiency of cotton

0.70

0.80

0.90

1.00

1.10

1.20

1.30


1 kg B ha-1 1.5 kg B ha-1 2 kg B ha-1 2.5 kg B ha-1

0.70

0.80

0.90

1.00

1.10

1.20

1.30


1 kg B ha-1 1.5 kg B ha-1 2 kg B ha-1 2.5 kg B ha-1 (b) 2015

(a) 2014

284

Rela

tiv

e s

eed

co

tto

n y

ield

(%

)

Leaf boron concentration (µg g-1

DW)


yield in response to foliar applied mepiquat chloride and soil applied boron; M0:

control, M1: mepiquat chloride application at squaring, M2: mepiquat chloride

application at flowering

(c) M2

(a) M0

(b) M1

285

Rela

tiv

e s

eed

co

tto

n y

ield

(%

)

Soil applied boron (kg B ha-1

)


yield in response to foliar applied mepiquat chloride and soil applied boron; M0:

control, M1: mepiquat chloride application at squaring, M2: mepiquat chloride

application at flowering

(c) M2

(a) M0

(b) M1

286

287

modulated plant physiological mechanisms such as improved NAR and dry matter

partitioning to reproductive plant parts which led to enhanced uptake and accumulation of

B.

Mepiquat chloride application increased the B fertilizer requirement through soil

application. This might be due to higher boll retention by mepiquat chloride application

that demanded higher amount of B for sustaining the higher crop yield. Moreover, mepiquat

chloride enhanced the uptake and translocation of B resulting in improved crop yield that

led to a higher demand of B fertilizer.

4.2.23. Soil bioassay

4.2.23.1. Emergence and seedling growth of progeny

Emergence and seedling growth of progeny significantly differed by soil

application of B and foliar application of mepiquat chloride on maternal plants; however,

their interactive effect was non-significant, during both years (Tables 4.369, 4.370). The

results revealed that soil application of B to maternal plants resulted in improved final

emergence, emergence index, root length and shoot length of progeny seedlings while

declined the mean emergence time, as compared to control. Highest final emergence

percentage (73 and 72% during 2015 and 2016, respectively) and emergence index (1.59

and 1.55 during 2015 and 2016, respectively), and lowest mean emergence time (4.43 and

4.78 days during 2015 and 2016, respectively) of progeny was recorded by application of

2.5 kg B ha-1 on maternal plants. Similarly, the greatest increase in root length (13-14%)

and shoot length (10-11%) of progeny seedlings was noticed by same treatment of maternal

plants. However, the effect of 1.5-2.5 kg B ha-1 was statistically at par for all these

emergence and seedling growth traits (Tables 4.371-4.380). Likewise, emergence and

seedling growth of progeny was improved in response to foliar applied mepiquat chloride

on maternal plants, as compared to control, during both years. Application of mepiquat

chloride at squaring stage on maternal plants was most superior in improving the final

emergence (72 and 71% during 2015 and 2016, respectively), emergence index (1.56 and

1.51 during 2015 and 2016, respectively), and root length (9-10%) and shoot length (6-7%)

of offspring seedlings. Whereas minimum mean emergence time (4.46 and 4.80 during

2015 and 2016, respectively) was also recorded by same treatment. However, the effect of

mepiquat chloride application at flowering stage was statistically similar for all these traits

(Tables 4.371-4.380).

288









Table 4.371: Maternal induced changes in final emergence percentage (%) of cotton

progeny in response to foliar applied mepiquat chloride and soil applied boron (2015)


Table 4.372: Maternal induced changes in final emergence percentage (%) of cotton




Mean sum of squares

Final

emergence

percentage

Mean

emergence

time

Emergence

index

Root

length

Shoot

length

Boron (B) 4 138.89** 0.095** 0.075** 1.386** 5.036** Mepiquat chloride (M) 2 135.56* 0.106* 0.087** 2.138** 5.505* B×M 8 18.89ns 0.005ns 0.004ns 0.075ns 0.325ns Error 30 28.89 0.022 0.014 0.255 1.105 Total 44


Mean sum of squares

Final

emergence

percentage

Mean

emergence

time

Emergence

index

Root

length

Shoot

length

Boron (B) 4 142.222** 0.064* 0.053* 1.229** 4.468* Mepiquat chloride (M) 2 242.222** 0.073* 0.096* 1.346** 5.866* B×M 8 8.889ns 0.004ns 0.011ns 0.084ns 0.467ns

Error 30 26.667 0.016 0.011 0.144 1.365 Total 44


at squaring

MC application

at flowering

Mean (B)

Control 63.33 66.67 63.33 64.44 C

1 kg B ha-1

63.33 66.67 66.67 65.56 BC 1.5 kg B ha

-1 66.67 73.33 66.67 68.89 ABC

2 kg B ha-1

70.00 76.67 70.00 72.22 AB 2.5 kg B ha

-1 66.67 76.67 76.67 73.33 A

Mean (MC) 66.00 B 72.00 A 68.67 AB


at squaring

MC application

at flowering

Mean (B)

Control 60.00 66.67 63.33 63.33 B 1 kg B ha

-1 60.00 66.67 63.33 63.33 B

1.5 kg B ha-1

63.33 70.00 66.67 66.67 AB 2 kg B ha

-1 66.67 76.67 66.67 70.00 AB

2.5 kg B ha-1

66.67 76.67 73.33 72.22 A

Mean (MC) 63.33 B 71.33 A 66.67 AB

289

Table 4.373: Maternal induced changes in mean emergence time (days) of cotton



Table 4.374: Maternal induced changes in mean emergence time (days) of cotton



Table 4.375: Maternal induced changes in emergence index of cotton progeny in

response to foliar applied mepiquat chloride and soil applied boron (2015)


Table 4.376: Maternal induced changes in emergence index of cotton progeny in




at squaring

MC application

at flowering

Mean (B)

Control 4.78 4.58 4.69 4.68 A 1 kg B ha

-1 4.67 4.51 4.65 4.61 AB

1.5 kg B ha-1

4.57 4.48 4.60 4.55 AB 2 kg B ha

-1 4.52 4.36 4.51 4.46 B

2.5 kg B ha-1

4.55 4.35 4.39 4.43 B

Mean (MC) 4.62 A 4.46 B 4.57 AB


at squaring

MC application

at flowering

Mean (B)

Control 5.11 4.90 4.99 5.00 A 1 kg B ha

-1 4.94 4.83 4.84 4.87 AB

1.5 kg B ha-1

4.90 4.81 4.90 4.87 AB 2 kg B ha

-1 4.85 4.77 4.80 4.81 B

2.5 kg B ha-1

4.89 4.69 4.77 4.78 B Mean (MC) 4.94 A 4.80 B 4.86 AB


at squaring

MC application

at flowering

Mean (B)

Control 1.33 1.43 1.36 1.37 C 1 kg B ha

-1 1.36 1.46 1.42 1.41 BC

1.5 kg B ha-1

1.44 1.60 1.48 1.51 ABC

2 kg B ha-1

1.47 1.64 1.54 1.55 AB 2.5 kg B ha

-1 1.45 1.68 1.64 1.59 A

Mean (MC) 1.41 C 1.56 A 1.49 AB


at squaring

MC application

at flowering

Mean (B)

Control 1.27 1.46 1.39 1.37 B 1 kg B ha

-1 1.32 1.32 1.46 1.37 B

1.5 kg B ha-1

1.36 1.50 1.44 1.44 AB 2 kg B ha

-1 1.41 1.60 1.46 1.49 AB

2.5 kg B ha-1

1.41 1.65 1.57 1.55 A Mean (MC) 1.35 B 1.51 A 1.47 A

290

Table 4.377: Maternal induced changes in root length (cm) of cotton progeny in




Table 4.378: Maternal induced changes in root length (cm) of cotton progeny in




Table 4.379: Maternal induced changes in shoot length (cm) of cotton progeny in




Table 4.380: Maternal induced changes in shoot length (cm) of cotton progeny in





at squaring

MC application

at flowering

Mean (B)

Control 7.39 7.89 7.75 7.68 B 1 kg B ha

-1 7.71 8.22 7.99 7.97 AB

1.5 kg B ha-1

7.90 8.52 8.23 8.22 AB 2 kg B ha

-1 8.07 9.00 8.48 8.52 A

2.5 kg B ha-1

8.00 9.20 8.71 8.64 A

Mean (MC) 7.81 B 8.57 A 8.23 AB


at squaring

MC application

at flowering

Mean (B)

Control 6.15 6.75 6.51 6.47 C 1 kg B ha

-1 6.45 6.83 6.84 6.71 BC

1.5 kg B ha-1

6.86 7.19 6.97 7.01 AB 2 kg B ha

-1 6.93 7.58 7.07 7.19 AB

2.5 kg B ha-1

6.94 7.97 7.28 7.39 A

Mean (MC) 6.67 B 7.27 A 6.93 AB


at squaring

MC application

at flowering

Mean (B)

Control 18.14 19.15 18.67 18.66 B 1 kg B ha

-1 18.64 19.47 19.05 19.05 B

1.5 kg B ha-1

19.07 19.95 19.53 19.51 AB 2 kg B ha

-1 19.32 20.74 19.95 20.00 AB

2.5 kg B ha-1

19.31 21.14 21.18 20.54 A

Mean (MC) 18.90 B 20.09 A 19.67 AB


at squaring

MC application

at flowering

Mean (B)

Control 15.83 17.04 16.63 16.50 C 1 kg B ha

-1 16.51 17.17 17.36 17.01 BC

1.5 kg B ha-1

17.11 17.77 17.37 17.42 AB 2 kg B ha

-1 17.30 18.66 17.58 17.85 AB

2.5 kg B ha-1

17.14 19.47 18.31 18.31 A Mean (MC) 16.78 B 18.03 A 17.45 AB

291

4.2.23.2. Biomass accumulation in progeny seedlings

Fresh and dry biomass accumulation in progeny seedlings as well as seedling vigour

index significantly differed by soil application of B, foliar application of mepiquat chloride

and their interaction on maternal plants. However, root/shoot ratio of progeny seedlings

was not affected by application of B, mepiquat chloride as well as their interaction on

maternal plants, during both years (Tables 4.381, 4.382). Root and shoot biomass and

seedling vigour index of offspring was improved by soil application of B and foliar applied

mepiquat chloride alone as well as in combination on maternal plants. It was found that

application of 2.5 kg B ha-1 in combination with mepiquat chloride application at squaring

stage on maternal plants resulted in improved root fresh (27-32%) and dry biomass (29-

36%), shoot fresh (28-32%) and dry biomass (29-36%), and seedling vigour index (44-

59%) of progeny seedlings. However, application of 2.5 kg B ha-1 in combination with

mepiquat chloride application at flowering stage as well as application of 2 kg B ha-1 in

combination with mepiquat chloride application at squaring stage on maternal plants

produced similar results in progeny seedlings (Tables 4.383-4.390, 4.393, 4.394).

4.2.24. Discussion

Emergence and seedling growth of progeny was improved in response to soil

fertilization of B and foliar application of mepiquat chloride on maternal cotton plants. The

final emergence of progeny seedlings was enhanced along with decrease in mean

emergence time and increase in seedling vigour index. This might be attributed to improved

seed size by application of B and mepiquat chloride through enhanced translocation of

photo-assimilates. It has been observed that seed quality in terms of seed germination and

vigour is much more dependent on seed size (van Mölken et al. 2005). Moreover, maternal

plants improve the performance of offspring in terms of emergence and seedling vigour

through enhanced deposition of nutrients (Li et al., 2017). In this study it was observed that

B contents were enhanced in seed obtained from maternal plants in response to B and

mepiquat chloride application. In seeds, during germination process B causes the

remobilization of stored nutrient reserves (Bonilla et al., 2004). Moreover, B regulates α-

amylase activity by regulating the synthesis of gibberellic acid in germinating seeds and

modulates the germination metabolism and translocation of carbohydrates from the

endosperm to developing embryo (Cresswell and Nelson, 1972, 1973). Soil application of

B and foliage applied mepiquat chloride produced progeny seedlings with better growth

and development. This might be due to enhanced assimilate and nutrient translocation to

developing seeds that produced healthy and vigorous seedlings.

292


cotton progeny in response to foliar applied mepiquat chloride and soil applied boron

(2015)



cotton progeny in response to foliar applied mepiquat chloride and soil applied boron

(2016)


Table 4.383: Maternal induced changes in root fresh weight (mg) of cotton progeny

in response to foliar applied mepiquat chloride and soil applied boron (2015)


Table 4.384: Maternal induced changes in root fresh weight (mg) of cotton progeny




Mean sum of squares

Root

fresh

weight

Shoot

fresh

weight

Root

dry

weight

Shoot dry

weight

Root/

shoot

ratio

Seedling

vigor

index

Boron (B) 4 640.57** 146256** 15.570** 1245.14** 0.00024ns 324310**


B×M 8 92.37* 18700** 1.642** 200.37* 0.00008ns 32199**

Error 30 31.19 4612 0.471 71.12 0.00105 8806

Total 44


Mean sum of squares

Root

fresh

weight

Shoot

fresh

weight

Root

dry

weight

Shoot dry

weight

Root/

shoot

ratio

Seedling

vigor

index

Boron (B) 4 671.33** 61675** 9.489** 1071.61** 0.00016ns 257713**


B×M 8 80.30** 11686* 1.661** 177.35** 0.00001ns 17758*

Error 30 21.15 4002 0.345 32.50 0.00117 6963

Total 44


at squaring

MC application

at flowering

Mean (B)

Control 121.11 e 128.45 de 126.33 de 125.30 B 1 kg B ha

-1 125.53 de 132.10 cde 131.06 de 129.56 B

1.5 kg B ha-1

127.87 de 137.40 b-e 131.09 cde 132.12 B 2 kg B ha

-1 129.60 de 152.60 ab 141.80 bcd 141.33 A

2.5 kg B ha-1

129.07 de 159.93 a 147.87 abc 145.62 A Mean (MC) 126.64 C 142.10 A 135.63 B


at squaring

MC application

at flowering

Mean (B)


-1 118.72 cd 122.00 cd 122.34 cd 121.02 BC

1.5 kg B ha-1

121.50 cd 129.01 bc 122.99 bcd 124.50 B 2 kg B ha

-1 123.42 bcd 142.61 a 135.49 ab 133.84 A

2.5 kg B ha-1

123.60 bcd 145.80 a 146.20 a 138.53 A Mean (MC) 120.44 B 132.24 A 129.00 A

293

Table 4.385: Maternal induced changes in shoot fresh weight (mg) of cotton progeny



at squaring

MC application

at flowering

Mean (B)


-1 1697.77 de 1760.94 cde 1716.52 cde 1725.08 BC

1.5 kg B ha-1

1756.31 cde 1879.89 bcd 1793.36 cde 1809.85 B 2 kg B ha

-1 1766.66 cde 2031.44 ab 1929.06 abc 1909.06 A

2.5 kg B ha-1

1744.19 cde 2139.45 a 2086.63 ab 1990.09 A Mean (MC) 1717.03 B 1906.98 A 1845.57 A



Table 4.386: Maternal induced changes in shoot fresh weight (mg) of cotton progeny

in response to foliar applied mepiquat chloride and soil applied boron (2016) Treatments Control MC application

at squaring

MC application

at flowering

Mean (B)

Control 1428.28 d 1518.15 cd 1488.87 d 1478.43 C 1 kg B ha

-1 1497.45 d 1533.55 cd 1530.11 cd 1520.37 C

1.5 kg B ha-1

1527.69 cd 1595.40 bcd 1530.88 cd 1551.32 BC 2 kg B ha

-1 1539.89 cd 1760.68 ab 1603.57 bcd 1634.72 AB

2.5 kg B ha-1

1511.53 cd 1829.84 a 1698.21 abc 1679.86 A Mean (MC) 1500.97 C 1647.53 A 1570.33 B



Table 4.387: Maternal induced changes in root dry weight (mg) of cotton progeny in



at squaring

MC application

at flowering

Mean (B)


-1 15.69 de 16.30 de 15.89 de 15.96 BC

1.5 kg B ha-1

16.00 de 17.57 bcd 16.65 cde 16.74 B 2 kg B ha

-1 16.72 cde 19.54 ab 18.40 bc 18.22 A

2.5 kg B ha-1

16.35 cde 20.57 a 18.92 ab 18.61 A Mean (MC) 15.97 C 18.05 A 17.11 B



Table 4.388: Maternal induced changes in root dry weight (mg) of cotton progeny in

response to foliar applied mepiquat chloride and soil applied boron (2016) Treatments Control MC application

at squaring

MC application

at flowering

Mean (B)

Control 13.88 d 14.86 cd 14.81 cd 14.52 B 1 kg B ha

-1 14.36 d 15.17 cd 15.36 cd 14.96 B

1.5 kg B ha-1

14.77 cd 15.33 cd 15.50 cd 15.20 B 2 kg B ha

-1 14.84 cd 18.10 a 16.23 bc 16.39 A

2.5 kg B ha-1

14.95 cd 17.96 ab 17.96 ab 16.96 A

Mean (MC) 14.56 B 16.28 A 15.97 A Values sharing the same case letters do not differ significantly at p ≤ 0.05; MC: Mepiquat chloride, B:


294

Table 4.389: Maternal induced changes in shoot dry weight (mg) of cotton progeny in



at squaring

MC application

at flowering

Mean (B)

Control 173.27 c 184.56 cd 185.69 cd 181.17 D 1 kg B ha

-1 181.00 cd 191.39 cd 189.67 cd 187.35 CD

1.5 kg B ha-1

188.11 cd 200.35 ab 203.88 ab 197.45 BC 2 kg B ha

-1 191.71 cd 217.89 a 200.10 ab 203.23 AB

2.5 kg B ha-1

184.05 cd 223.15 a 223.70 a 210.30 A Mean (MC) 183.63 B 203.47 A 200.61 A



Table 4.390: Maternal induced changes in shoot dry weight (mg) of cotton progeny in

response to foliar applied mepiquat chloride and soil applied boron (2016) Treatments Control MC application

at squaring

MC application

at flowering

Mean (B)

Control 146.16 e 158.82 cde 154.42 cde 153.14 D 1 kg B ha

-1 151.73 de 163.89 cde 164.51 cd 160.05 CD

1.5 kg B ha-1

154.70 cde 171.08 bc 166.48 cd 164.09 BC 2 kg B ha

-1 157.81 cde 186.84 ab 170.35 bc 171.66 B

2.5 kg B ha-1

154.72 cde 198.99 a 190.73 a 181.48 A Mean (MC) 153.02 C 175.92 A 169.30 B



Table 4.391: Maternal induced changes in root/shoot ratio of cotton progeny in



Table 4.392: Maternal induced changes in root/shoot ratio of cotton progeny in




at squaring

MC application

at flowering

Mean (B)

Control 0.41 0.41 0.42 0.41

1 kg B ha-1

0.41 0.42 0.42 0.42 1.5 kg B ha

-1 0.42 0.43 0.42 0.42

2 kg B ha-1

0.42 0.43 0.43 0.43 2.5 kg B ha

-1 0.41 0.44 0.41 0.42

Mean (MC) 0.41 0.43 0.42


at squaring

MC application

at flowering

Mean (B)

Control 0.40 0.40 0.39 0.40 1 kg B ha

-1 0.39 0.40 0.39 0.40

1.5 kg B ha-1

0.40 0.40 0.40 0.40 2 kg B ha

-1 0.40 0.41 0.40 0.40

2.5 kg B ha-1

0.40 0.41 0.40 0.40 Mean (MC) 0.40 0.40 0.40

295

Table 4.393: Maternal induced changes in seedling vigour index of cotton progeny in





Table 4.394: Maternal induced changes in seedling vigour index of cotton progeny in






at squaring

MC application

at flowering

Mean (B)

Control 1613.83 f 1796.38 def 1667.21 ef 1692.47 C 1 kg B ha

-1 1665.24 ef 1841.10 c-f 1798.97 c-f 1768.44 C

1.5 kg B ha-1

1793.21 def 2083.86 abc 1848.31 c-f 1908.46 B 2 kg B ha

-1 1917.00 cde 2275.79 ab 1989.90 bcd 2060.90 A

2.5 kg B ha-1

1814.46 c-f 2323.83 a 2289.57 a 2142.62 A

Mean (MC) 1760.75 C 2064.19 A 1918.79 B


at squaring

MC application

at flowering

Mean (B)

Control 1318.83 f 1584.03 cde 1459.67 def 1454.18 C 1 kg B ha

-1 1377.66 ef 1596.18 cde 1526.89 c-f 1500.24 C

1.5 kg B ha-1

1515.36 c-f 1747.58 bc 1620.15 cde 1627.70 B

2 kg B ha-1

1610.07 cde 2006.61 a 1639.95 bcd 1752.21 A 2.5 kg B ha

-1 1604.53 cde 2098.84 a 1872.14 ab 1858.51 A

Mean (MC) 1485.29 C 1806.65 A 1623.76 B

296

In this study, the interactive effect of maternal soil fed B and foliar applied mepiquat

chloride resulted in increased biomass accumulation in roots and shoots of progeny. It has

been observed that B deficiency causes a reduction in dry matter production and

accumulation (Zhao and Oosterhuis, 2003); however, B nutrition has been observed to

improve the dry matter production and accumulation in plants (Ahmed et al., 2011). Boron

application enhances leaf photosynthetic activity, which consequently leads to greater

accumulation and partitioning of dry matter (Qiong et al., 2002). The increase in photo-

assimilation and translocation to developing seeds results in improved seed size and

ultimately better growth and biomass production in progeny seedlings (Dordas, 2006a).

Similarly, mepiquat chloride application improves the biomass accumulation in progeny

seedlings. Sawan et al. (2009) reported that mepiquat chloride application improved the

seedling fresh and dry weights in response to residual effect of mepiquat chloride on cotton.

4.2.25. Regression and correlation analysis

The NAWF and NACB were positively correlated with mean maturity days while

negatively associated with earliness index, during both years. The regression coefficients

showed variation in mean maturity days and earliness index due to NAWF by 64 and 88%,

during 2014 and 2015, respectively. Whereas, the corresponding values exhibiting

variation in mean maturity days and earliness index due to NACB were 75 and 87%, during

2014 and 2015, respectively (Table 4.395). Mean maturity days were significantly and

negatively correlated with earliness index and production rate index, during both years. It

was observed that earliness index and production rate index varied by 99% during both

years, and 87 and 79% during 2014 and 2015, respectively, by mean maturity days (Table

4.395).

The CGR was positively correlated with boll weight and seed cotton yield, during

both years. The seed cotton yield varied by 55 and 37% due to crop growth rate during

2014 and 2015, respectively (Table 4.395). The total chlorophyll content was positively

associated with NAR and the corresponding values of variation for NAR were 54 and 52%,

during 2014 and 2015, respectively (Table 4.395). In turn, NAR was positively associated

with boll weight and seed cotton yield, during both years. The coefficient of determination

explained 43 and 38% variation in boll weight while 40 and 51% variation in seed cotton

yield due to NAR, during 2014 and 2015, respectively (Table 4.395). Likewise,

reproductive and TDM accumulation was positively correlated with seed cotton yield

during both years. The seed cotton yield varied by 78 and 84% due to reproductive dry

matter accumulation, during 2014 and 2015, respectively (Table 4.395). Boll weight,

297


goodness of fit and association strength between different variables

*: Significant at p 0.1; **: Significant at p 0.05; ***: significant at p 0.01

X-variable Y-variable 2014 2015

R2 r R

2 r







CGR Boll weight 0.50 0.71*** 0.30 0.55**

CGR Seed cotton yield 0.55 0.74*** 0.37 0.61**

Total chlorophyll NAR 0.54 0.73*** 0.52 0.72***

NAR Boll weight 0.43 0.66** 0.38 0.62**

NAR Seed cotton yield 0.40 0.63** 0.51 0.71***


TDM Seed cotton yield 0.52 0.72*** 0.36 0.60**

Boll weight Seed cotton yield 0.88 0.94*** 0.95 0.97***

Opened bolls per plant Seed cotton yield 0.92 0.96*** 0.97 0.98***

No. of seeds Seed cotton yield 0.88 0.94*** 0.88 0.94***


No. of seeds Ginning out turn 0.63 0.79*** 0.67 0.82***







298

number of opened bolls per plant and number of seeds per boll were also significantly and

positively correlated with seed cotton yield, during both years. Seed cotton yield varied by

88, 92 and 88% during 2014 while by 95, 97 and 88% due to boll weight, number of opened

bolls per plant and number of seeds per boll, respectively, during 2015 (Table 4.395). A

significant correlation was observed between seed B content and seed cotton yield, during

both years, and coefficient of determination explained 90 and 87% variation, during 2014

and 2015, respectively (Table 4.395.

Number of seeds per boll and seed B contents were significantly associated with

ginning out turn during both years. Ginning out turn was positively varied by 63 and 71%

by number of seeds per boll and seed B content, respectively, during 2014 and by 67 and

74%, respectively, during 2015 (Table 4.395). There was positive correlation between

number of seeds and final emergence, seed index and final emergence, and seed B content

and final emergence of progeny seedlings during both years. Coefficient of determination

explained a variation in final emergence by 87, 86 and 84% during 2014 and 83, 89 and

84% during 2015 due to number of seeds per boll, seed index and seed B content,

respectively (Table 4.395). Seed B content positively correlated with root dry biomass and

shoot dry biomass of progeny seedlings, during both years, and the corresponding values

of variation were 94 and 85% during 2014, and 81 and 85% during 2015, as explained by

coefficient of determination (Table 4.395).

4.2.26. Economic analysis

The economic analysis revealed that soil application of B and foliar applied

mepiquat chloride improved the economic returns and BCR when applied alone; while,

their application in combination caused more improvement than their sole application. It

was observed that application of 2.5 kg B ha-1 in combination with mepiquat chloride at

squaring stage was most effective in improving the net returns (worth Rs. 86425) and BCR

(1.63) (Table 4.396). This is attributed to enhanced seed cotton yield which enhanced the

net profit and ultimately BCR. Marginal analysis further revealed that the most economical

treatment was application of B in combination with mepiquat chloride as compared to their

sole application. However, highest MRR (2515%) was produced by 2 kg B ha-1 + mepiquat

chloride application at squaring stage (Table 4.397); thus this treatment combination can

be adopted at farmer level to get higher economic benefits because of less cost of

production and greater net returns. Similar increase in economic returns and value cost ratio

have been reported by Ahmed et al. (2013) by B application, and Prakash and Prasad (2000)

by a plant growth retardant (chlormequat chloride) application on cotton.

299

Table 4.396: Economic analysis

Adjusted yield: 10% less than actual yield; Income was estimated by using the prevailing market prices for seed cotton in Pakistan; B: Boron;

MC: Mepiquat chloride; BCR: Benefit cost ratio

Treatment Yield

(kg ha-1

)

Adjusted

yield

(kg ha-1

)

Gross

income

(Rs.)

Fixed cost

(Rs.)

Variable

cost (Rs.)

Total cost

(Rs.)

Net

returns

(Rs.)

BCR

Control 2172 1955 162923 120160 9164 129324 33598 1.26 1 kg B ha-1 2285 2057 171408 120160 10818 130977 40430 1.31 1.5 kg B ha-1 2348 2113 176073 120160 11668 131828 44245 1.34

2 kg B ha-1 2415 2174 181144 120160 12541 132701 48443 1.37 2.5 kg B ha-1 2398 2158 179844 120160 13056 133216 46628 1.35 MC at squaring 2379 2141 178440 120160 10727 130887 47553 1.36 MC at flowering 2317 2085 173770 120160 10484 130644 43126 1.33 MC at squaring + 1 kg B ha-1 2444 2200 183325 120160 12178 132338 50987 1.39 MC at flowering + 1 kg B ha-1 2393 2154 179482 120160 11980 132139 47343 1.36 MC at squaring + 1.5 kg B ha-1 2606 2345 195434 120160 13447 133607 61827 1.46

MC at flowering + 1.5 kg B ha-1 2479 2231 185898 120160 12996 133156 52743 1.40 MC at squaring + 2 kg B ha-1 2811 2529 210788 120160 14859 135019 75769 1.56 MC at flowering + 2 kg B ha-1 2663 2397 199712 120160 14436 134595 65116 1.48 MC at squaring + 2.5 kg B ha-1 2970 2673 222744 120160 16159 136319 86425 1.63 MC at flowering + 2.5 kg B ha-1 2827 2545 212052 120160 15643 135803 76249 1.56

300

Table 4.397: Marginal analysis

B: Boron; MC: Mepiquat chloride

Treatments Variable

cost

(Rs.)

Marginal

variable

cost (Rs.)

Net

benefits

(Rs.)

Marginal

net

benefit

(Rs.)

Marginal

rate of

return

(%)

Control 9164 - 153758 - - MC at flowering 10484 1320 163286 9528 722

MC at squaring 10727 243 167713 4427 1823 1 kg B ha-1 10818 90 160590 - D 1.5 kg B ha-1 11668 850 164405 - D MC at flowering + 1 kg B ha-1 11980 311 167503 - D MC at squaring + 1 kg B ha-1 12178 198 171147 3434 1730 2 kg B ha-1 12541 363 168602 - D MC at flowering + 1.5 kg B ha-1 12996 454 172903 1755 386

2.5 kg B ha-1 13056 60 166788 - D MC at squaring + 1.5 kg B ha-1 13447 391 181987 9085 2324 MC at flowering + 2 kg B ha-1 14436 988 185276 3289 333 MC at squaring + 2 kg B ha-1 14859 424 195929 10653 2515 MC at flowering + 2.5 kg B ha-1 15643 784 196409 480 61 MC at squaring + 2.5 kg B ha-1 16159 516 206585 10176 1970

301

CHAPTER 5

SUMMARY

Studies on plant growth regulation and B nutrition for improving earliness,

productivity, quality and nutrient dynamics of cotton were conducted in two field

experiment at Agronomic Research Area, Department of Agronomy, University of

Agriculture, Faisalabad and two pot experiments at Agro-Biology Lab Department of

Agronomy, University of Agriculture, Faisalabad, Pakistan. In first field experiment the

treatments were two planting densities (55333 and 88888 plants ha-1 maintained by varying

the plant spacing i.e. 25 and 15 cm, respectively), foliar application of mepiquat chloride

solution (0 and 70 ppm at squaring and flowering stage) and foliar application of B solution

(0, 600 and 1200 ppm). In second field experiment treatments were foliar application of

mepiquat chloride solution (0 and 70 ppm at squaring and flowering stage) and soil

application of B (0, 1, 1.5, 2 and 2.5 kg ha -1). Water was sprayed as control in both

experiments. Field experiments were laid out by using randomized complete block design

(RCBD) with factorial arrangement each replicated thrice. Plot size was 6 m × 3 m. Crop

was sown with the help of dibbler keeping row to row distance of 75 cm. Basal dose of

NPK at the rate of 200-120-110 kg ha-1 was applied. Data regarding growth, allometry,

phenology, yield, fiber quality, cotton seed nutritional quality and leaf and cotton seed

tissue nutrient contents was recorded using standard procedures. Moreover, NUE of B,

critical concentration of B in leaf tissues of cotton and B fertilizer requirement of cotton

was also determined. In pot experiments seed obtained from both field experiments was

used for a soil bioassay to determine the effect of maternal B nutrition, growth regulation

and planting density induced changes on progeny performance in terms of emergence and

seedling growth. The pot experiments were laid out in completely randomized design

(CRD) with factorial arrangement and three replications. The data regarding emergence,

growth and dry matter production in progeny seedlings was collected using standard

procedures. The data recorded was analyzed using standard statistical procedures. The

important results obtained are summarized in following sections.

302

Experiment 1: Influence of foliar applied mepiquat chloride and boron on growth,

productivity and earliness of cotton at different planting densities

Plant growth and architecture

Foliar application of B improved plant growth at both planting densities with

maximum growth increase occurring by application of 1200 ppm B solution, as

compared to control.

Mepiquat chloride application decreased plant growth at all levels of B and both

planting density with highest growth reduction caused by mepiquat chloride

application at squaring stage, as compared to control.

Increase in planting density than normal increased the plant height and internodes

length while decreased the number of main stem nodes, and vegetative and fruiting

branches.

The NAWF and NACB were decreased by interactive effect of B and mepiquat

chloride. Maximum decrease in NAWF (26-32%) and NACB (26-32%) was caused

by application of 1200 ppm B in combination with mepiquat chloride application at

squaring stage, as compared to control.

Higher planting density also caused a reduction in NAWF (6-9%) and NACB (8-

9%), as compared to lower planting density.

Phenology

Boron application caused earlier commencement of flowering (≈2-2.4 days) and

boll opening (2.3-2.8 days) with increase in earliness index (5-8%) and 1200 ppm

B solution was most effective, as compared to control.

Similarly, earlier flowering (3 days) and boll opening (3-3.4 days) initiated along

with enhanced earliness index (7-8%) by application of mepiquat chloride at


Increasing the planting density enhanced earliness index (3-4%) by earlier

flowering (1.5-2.2 days) and boll opening initiation (3 days), as compared to lower

planting density.

Compared with control, the heat units accumulation for commencement of boll

opening was decreased by 1200 ppm B (37-39 GDD), mepiquat chloride application

at squaring stage (49 GDD) and higher planting density (41-50 GDD).

Foliar application of B and mepiquat chloride interactively increased the production

rate index (34-39%), as compared to control.

303

Higher planting density in combination with foliar B substantially improved the

production rate index (16 and 18% at lower and higher planting density,

respectively), as compared to control.

Allometric attributes

Vegetative (10-14%), reproductive (18-20%) and total dry matter accumulation

(13-16%) was improved by foliar application of B and application 1200 ppm B

solution was most effective, as compared to control.

Mepiquat chloride application decreased vegetative dry matter (13%), increased

reproductive dry matter (10-11%) while did not affect TDM and mepiquat chloride

application at squaring was most effective, as compared to control.

A substantially higher vegetative (14-21%), reproductive (18-23%) and total dry

matter (15-22%) was observed at higher planting density, as compared to lower

planting density.

Reproductive-vegetative dry matter ratio was substantially increased by foliar

application of B (1.46 and 1.21), mepiquat chloride (1.60 and 1.32) and higher

planting density (1.44 and 1.22), during 2014 and 2015, respectively.

Crop growth rate was enhanced by foliar applied B (15-19%) and increasing

planting density (10-17%) while remained unaffected by mepiquat chloride.

Highest LAI and LAD was observed by 1200 ppm B application and NAR was

improved non-significantly, as compared to control.

Mepiquat chloride application at squaring decreased the LAI and LAD but

increased the NAR most effectively, as compared to control.

Increasing the planting density increased the LAI and LAD but decreased the NAR,

as compared to control.

Boll distribution pattern

Foliar applied B and mepiquat chloride did not affect percentage of first position

bolls, decrease second position bolls while interactively increased the outer position

bolls at sympodial positions, as compared to control.

Application of 1200 ppm B and mepiquat chloride at squaring stage were proved

superior in affecting the boll distribution on sympodial branches.

Higher planting density increased the percent of first and second position bolls

while decreased the outer position bolls, as compared to lower planting density.

304

Yield and related attributes

Foliar applied B and mepiquat chloride synergistically improved the number of

bolls and boll weight resulting in improved seed cotton yield (30-35%), lint yield

(37-42%) and cotton seed yield (26-31%), as compared to control.

The number of seeds per boll and seed index was enhanced by application of B as

well as mepiquat chloride, as compared to control.

Application of 1200 ppm B + mepiquat chloride at squaring stage proved most

effective in in improving yield and related traits, as compared to control.

The bolls per plant, average boll weight, number of seeds per boll and seed index

was decreased by increasing the planting density.

However, yield was comparatively greater at higher planting density due to higher

boll density. Boron application interactively with higher planting density further

increased the seed cotton yield (15-19%), lint yield (19-24%) and cotton seed yield

(13-15%), as compared to control.

Fiber quality

Foliar application of B improved some of the fiber quality traits with highest

ginning out turn (39.7 and 38.9% during 2014 and 2015, respectively) by

application of 1200 ppm B.

Mepiquat chloride did not impose a significant effect at both normal and high

planting density.

Fiber quality was better to some extent at lower planting density than higher

planting density.

Photosynthetic pigments

Foliar application of B and mepiquat chloride interactively improved the

chlorophyll a (44-47%), chlorophyll b (53-57%), total chlorophyll (47-49%) and

carotenoids contents (36-46%), as compared to control.

The most effective combination was 1200 ppm B + mepiquat chloride application

at squaring stage.

The chlorophyll a, b, total chlorophyll and carotenoids contents were decreased by

6-15, 5-7, 6-13 and 9-11%, respectively, at higher planting density, as compared to

lower planting density.

305

Tissue nutrient contents

Maximum contents of macro and micronutrients (N, P, K, B, Zn and Fe) in leaf and

seed tissues of cotton was recorded by foliar application of 1200 ppm B as well as

mepiquat chloride application at squaring stage at both planting densities.

However, Mn contents in leaves and seed was decreased by application of B and

mepiquat chloride as well as at higher planting density.

Foliar application of B and mepiquat chloride application significantly interacted in

improving the leaf (59-63%) and seed B contents (59-60%).

Increasing the planting density decreased the uptake and translocation of nutrients.

However, B application positively interacted with planting density in improving the

uptake (29-38 and 40-42%) and translocation of B (28-35 and 36-38%), at lower

and higher planting density, respectively.

Cotton seed nutritional quality

An improvement in cotton seed oil (4-5%), protein (4-5%) and ash contents (5-6%)

was occurred by foliar application of B with maximum increase occurring by

application of 1200 ppm B, as compared to control.

Similarly, mepiquat chloride application at squaring was superior in enhancing the

oil (5-6%), protein (4%) and ash contents (7%), as compared to control.

Lower oil (4-5%), protein (2%) and ash contents (3%) were observed at higher

planting density, as compared to higher planting density.

The oil yield (41-42%) and protein yield (38-43%) was increased interactively by

application of 1200 ppm B + mepiquat chloride application at squaring stage, as

compared to control.

Despite of decrease in oil and protein contents at higher planting density the oil and

protein yield was increased due to higher cotton seed yield. Moreover, B application

interactively with higher planting density further increased the oil yield (19-20%)

and protein yield (19-20%), as compared to control.

Nutrient use efficiency and critical value of boron

The mepiquat chloride application improved the NUE of B and increased the critical

value of B, as compared to control.

Increasing the planting density lead to an increase in NUE but decreased the critical

value of B.

306

Highest, NUE of B i.e. 1.25 and 1.20, was observed by mepiquat chloride

application along with 1200 ppm B at higher planting density during 2014 and at

lower planting density during 2015, respectively.

Critical values of B without mepiquat chloride, with mepiquat chloride application

at squaring and mepiquat chloride application at flowering at lower planting density

were 34, 45 and 43 µg B g-1 dry leaves, while at higher planting density the critical

values were 31, 45, 41 µg B g-1 dry leaves, respectively.

Mepiquat chloride also increased the B fertilizer demand through foliar application,

as compared to control.

Moreover, higher planting density demanded higher amount of foliar B fertilizer.

At lower planting density the foliar B fertilizer required with control, mepiquat

chloride application at squaring and mepiquat chloride application at flowering

stage was 155 480 and 510 ppm B ha-1, respectively, while at higher planting

density it was 420, 1020 and 1015 ppm B ha-1, respectively.

Economic analysis

Foliar application of B and mepiquat chloride improved the net benefits and BCR,

and higher BCR was obtained by their application in combination at both planting

densities.

Increasing the planting density increased the net benefits as well as BCR (from 1.29

to 1.41) and application of B + mepiquat chloride further increased the BCR.

Highest BCR (1.83) was recorded by application of 1200 ppm B + mepiquat

chloride at squaring stage at higher planting density.

Highest MRR (2022%) was also recorded by the same treatment combination and

this treatment combination can be adopted at farmer level.

Soil bioassay: Influence of previously treated maternal cotton crop with foliar

application of mepiquat chloride and boron at various planting densities on

emergence and seedling growth of progeny

Progeny emergence and seedling growth

Maternal treatment with 1200 ppm B solution produced highest emergence and

growth of progeny seedlings with minimum time elapsed.

Mepiquat chloride application at squaring stage on maternal plants was most

effective in improving the progeny emergence and growth with maximum reduction

in mean emergence time.

307

Application of B and mepiquat chloride in combination on maternal plants was

more effective in improving emergence and seedling growth of progeny than their

application in alone.

Growing the maternal plants at higher planting density produced poor quality seeds

in terms of emergence and seedling growth of progeny.

Biomass accumulation in progeny seedlings

Foliar application of B and mepiquat chloride on maternal plants significantly

interacted in improving the root (26-28%) and shoot (27-28%) dry biomass

accumulation in progeny seedlings, as compared to control.

Application of 1200 ppm B + mepiquat chloride at squaring stage was most

effective in improving biomass production in progeny seedlings.

Maternal plants sown at higher planting density caused a reduction in root (11-18%)

and shoot (8-10%) dry biomass accumulation in progeny seedlings, as compare to

lower planting density.

Experiment 2: Influence of foliar application of mepiquat chloride and soil applied

boron on growth, productivity and earliness of cotton

Plant growth and architecture

Soil application of B improved plant growth with maximum growth increased by

application of 2.5 kg B ha-1, as compared to control.

Mepiquat chloride application decreased plant growth at all levels of soil applied B

and highest reduction in growth was caused by mepiquat chloride application at


Soil applied B and mepiquat chloride application positively interacted in decreasing

the NAWF (30-32%) and NACB (30%), as compared to control. Combination of

2.5 kg B ha-1 + mepiquat chloride application at squaring stage was most effective

in this regard.

Phenology

Early initiation of flowering (2.7-3 days) and boll opening (3.5-3.8 days)

accompanied by increased earliness index (6-7%) was caused by application 2 kg

B ha-1, as compared to control.

Similarly, early flowering (2-3 days) and boll opening (2.5-3.3 days) initiated along

with enhanced earliness index (5-7%) was caused by application of mepiquat

chloride at squaring stage, as compared to control.

308

A significant decrease in heat unit accumulation from sowing to boll opening

occurred by soil application of B (47-60 GDD) as well as foliar applied mepiquat

chloride at squaring stage (33-54 GDD), as compared to control.

Production rate index was substantially increased (37-44%) by interactive effect of

soil application of B (2.5 kg B ha-1) and foliage applied mepiquat chloride at

squaring, as compared to control.

Allometric attributes

Soil application of B resulted in an increase in accumulation of vegetative (14%),

reproductive (19-22%) and total dry matter (16-17%) with 2.5 kg B ha-1 being

superior in this regard.

On the other hand, there was a decrease in vegetative dry matter (9-12%) and

increase in reproductive dry matter (11-13%) by the effect of mepiquat chloride

application, as compared to control, while production of TDM was not affected.

Highest reproductive-vegetative dry matter ratio was produced by the effect of 2.5

kg B ha-1 (1.46 and 1.17 during 2014 and 2015, respectively) as well as mepiquat

chloride application at squaring stage (1.60 and 1.24 during 2014 and 2015,

respectively).

Similarly, the CGR (17-18%) was increased by soil application of B while remained

unaffected by mepiquat chloride application, as compared to control.

Highest LAI (3.44 and 3.77 during 2014 and 2015, respectively) and LAD (229 and

245 days during 2014 and 2015, respectively) were observed by 2.5 kg B ha-1 while

NAR was not affected significantly by soil applied boron.

Least LAI (3.10 and 3.38 during 2014 and 2015, respectively) and LAD (204 and

217 days during 2014 and 2015, respectively), and maximum increase in NAR (8-

10%) was recorded by mepiquat chloride application at squaring stage, as compared

to control.

All the allometric traits were affected most by 2.5 kg B ha-1 and mepiquat chloride

application at squaring stage.

Boll distribution pattern

Percent of first position bolls on sympodial branches was not affected significantly

by soil application of B as well as foliar applied mepiquat chloride.

309

However, the second position bolls were decreased in response to both B and

mepiquat chloride while outer position bolls were increased by interactive effect of

B and mepiquat chloride.

Yield and related attributes

A significant interaction occurred between soil applied B and foliage applied

mepiquat chloride regarding number of bolls, boll weight and yield [seed cotton

yield (34-40%), lint yield (40-48%) and cotton seed yield (30-34%)].

Soil application of B as well as foliar application of mepiquat chloride also

improved the number of seeds and seed index, as compared to control.

Application of 2.5 kg B ha-1 + mepiquat chloride at squaring stage proved most

beneficial in improving the yield and related traits, as compared to control.

Fiber quality

Fiber quality traits were found superior to some extent by soil application of B while

mepiquat chloride did not exert a significant effect.

The ginning out turn, fiber length and fiber maturity was significantly improved by

soil application of B.

The highest ginning out turn (40.3 and 39.2% during 2014 and 2015, respectively)

was achieved by application of 2.5 kg B ha-1.

Photosynthetic pigments

Photosynthetic pigments were significantly increased by soil application of B and

foliage applied mepiquat chloride alone as well as in interaction, as compared to

control.

The chlorophyll a (44-51%), chlorophyll b (54-63%) and total chlorophyll (49-

52%), and carotenoids contents (46-55%) were increased in response to combined

application of B and mepiquat chloride

Chlorophyll a/b ratio was decreased by soil application of B as well as foliar

application of mepiquat chloride, as compared to control.

The most effective combination was 2.5 kg B ha-1 + mepiquat chloride application

at squaring stage

Tissue nutrient contents

The contents of macronutrients (N, P and K) and micronutrients (B, Zn and Fe) in

leaves and cotton seed was were enhanced by soil application of 2.5 kg B ha -1 as

well as mepiquat chloride application at squaring stage, as compared to control.

310

Uptake (52-58%) and translocation (49-59%) of B was increased by interactive

effect of soil applied B and foliage applied mepiquat chloride, as compared to

control.

However, Mn contents in both leaves and seed tissues were decreased in response

to B as well as mepiquat chloride application, as compared to control.

Cotton seed nutritional quality

Soil application of B improved the cotton seed oil (4-6%), protein (5%) and ash

contents (6-7%), as compared to control.

Similarly, foliage applied mepiquat chloride improved the cotton seed oil (4-5%),

protein (4%) and ash contents (6-8%), as compared to control.

Maximum improvement in cotton seed nutritional quality was recorded by

application of 2.5 kg B ha-1 and mepiquat chloride application at squaring stage.

The interactive effect of soil applied B and foliar applied mepiquat chloride was

significant in improving the cotton seed oil yield (46-47%) and protein yield (42-

47%), as compared to control.

Nutrient use efficiency and critical value of boron

Mepiquat chloride application enhanced the NUE of soil applied B, as compared to

control.

Highest NUE of B (1.27 and 1.23 during 2014 and 2015, respectively) was recorded

by application of mepiquat chloride at squaring stage + 2.5 kg B ha -1.

Mepiquat chloride application also increased the critical value of B and requirement

of soil applied B, as compared to control.

The critical value of B with control (no mepiquat chloride), mepiquat chloride

application at squaring stage and mepiquat chloride application at flowering stage

was 34, 46 and 43 µg g-1 dry leaves, respectively.

The B fertilizer requirement of cotton with control (no mepiquat chloride),

mepiquat chloride application at squaring stage and mepiquat chloride application

at flowering stage was 1, 2.1 and 2.1 kg B ha-1, respectively.

Economic analysis

Higher net benefits and BCR was obtained by soil application of B and foliar

application of mepiquat chloride.

Application of B and mepiquat chloride in combination was more effective in

improving the BCR.

311

The highest BCR (1.60) was noticed by application of 2.5 kg B ha-1 + mepiquat

chloride application at squaring stage.

However, marginal analysis revealed that highest MRR (2515%) was obtained by

2 kg B ha-1 + mepiquat chloride application at squaring stage and this treatment

combination can be adopted at farmer level.

Soil bioassay: Influence of previously treated maternal cotton crop with foliar

application of mepiquat chloride and soil applied boron on emergence and seedling

growth of progeny

Progeny emergence and seedling growth

Soil application of B and foliar application of mepiquat chloride on maternal plants

enhanced the emergence and seedling growth of progeny with reduction in mean

emergence time, as compared to control.

Application of 2.5 kg B ha-1 and mepiquat chloride application at squaring stage on

maternal plants was most effective in improving the progeny emergence and

seedling growth.

The effect of B and mepiquat chloride in combination was more effective in

improving emergence and seedling growth than their sole application although their

interaction was non-significant.

Biomass accumulation in progeny seedlings

Biomass accumulation in progeny seedlings was higher by maternal treatment with

soil applied B and foliage applied mepiquat chloride.

Both B and mepiquat chloride significantly interacted in improving the root and

shoot biomass accumulation in progeny seedlings.

Highest improvement in root (29-36%) and shoot (29-36%) dry biomass production

in progeny was caused by application of 2.5 kg B ha-1 + mepiquat chloride

application at squaring stage on maternal plants.

Likewise, seedling vigour index (44-59%) of progeny was improved most by

application of 2.5 kg B ha-1 + mepiquat chloride application at squaring stage on

maternal plants, as compared to control.

312

Conclusion

Application of B both by foliar and soil application in combination with mepiquat

chloride improved the earliness, yield, cotton seed quality, and nutrient uptake and

translocation. Moreover, increasing the planting density enhanced the earliness, lint yield,

oil yield and protein yield. Foliar application of B effectively improved the boll density at

higher planting density further adding to the lint and cotton seed yield. The fiber quality

was slightly decreased at higher planting density but B application imposed a positive

influence; while, mepiquat chloride did not impose any effect. It was observed that

application of B and mepiquat chloride in combination was more effective than their sole

application. Moreover, the mepiquat chloride improved the NUE of B by substantially

improving its uptake and translocation. The economic analysis further revealed that foliar

as well as soil application of B in combination with mepiquat chloride was more effective

in terms of economic benefits. Whereas, increasing the planting density enhanced the

economic benefits while application of B and mepiquat chloride further added to enhanced

benefits. The soil bioassay revealed that application of B (either by foliage application or

soil application) along with foliar application of mepiquat chloride on maternal plants

improved the performance of progeny in terms of emergence and early seedling growth

through improved seed development and nutrient accumulation in seed. However,

increasing the planting density of maternal plants decreased the seed quality in terms of

emergence and seedling growth of offspring. However, B and mepiquat chloride

application ameliorated the negative effects of higher planting density on seed quality in

terms of emergence and seedling growth of progeny.

313

Future research thrusts

Carbon dynamics in cotton plants in response to mepiquat chloride and B should be

studied.

Endogenous hormonal balance (auxin, gibberellic acid, cytokinins, abscisic acid) in

cotton plants in response to mepiquat chloride and B should be studied.

Physiological mechanism of nutrient uptake and translocation should be explored

in response to mepiquat chloride and B at different panting densities.

Performance of progeny of mepiquat chloride and B treated maternal cotton plants

at different panting densities should be evaluated in field conditions.

314

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APPENDICES

Appendix 1: Fixed cost (Rs. ha-1) (Experiment 1)

Sr.

No.

Operation/input No./Amount/Q

uantity per ha

Rate/unit (Rs.) Cost/ha (Rs.)

1 Sowing operations

1.1 Land preparation charges

Deep ploughing 1 3400 3400

Ploughing/cultivation 3 1475 4425

Planking 2 750 1500

Leveling 1 1700 1700

Sub total (a) 11025

1.2 Bed Planting

Bed shaper 1 3000 3000

Sowing via dibbling method 3 man days 400 1200

Sub total (b) 4200

2 Fertilizer cost

2.1 Fertilizer (bags)

Urea 6.6 1850 12210

DAP 5.21 3750 19538

SOP 3 2370 7110

2.2 Transportation charges 14.81 20/bag 296

2.3 Application charges (man days) 1 400 400

Sub total (c) 39554

3 Irrigation

Canal water charges (abiana/ha) - - 239

Private tubewell (rate/hour Rs. 330) per irrigation 2325

2 irrigations 2325/ha 4650

Sub total (d) 4889

4 Labour for irrigation

Water course cleaning and application

charges(man days) 3 man days 400 1200

Sub total (e) 1200

5 Interculture/hoeing

Manual weeding/thinning (man days) 10 man days 400 4000

Sub total (f) 4000

6 Plant protection including application (Weedicides + insecticides)

Glyphosate 1.5 L 950/L 1425

Imidachloprid 625 ml 1000/L 625

Acetamaprid 625 g 450/250 g 1125

Emamectin 500 ml 650/500 ml 650

Application charges (man days) 2 man days 400 800

Sub total (g) 4625

Grand total (a-g) 69493 7 Mark up on investment @ 9% per

annum on items for 8 months

(excluding water rate 3.1)

44626

-

4016

8 Land rent for 8 months @ Rs. 62500

per annum

8 months

5208

41664

9 Agricultural Income Tax for 8 months - - 162

10 Management Charges for 8 months @

Rs. 14000/month for 100 Acres

8 months

350

2800

Gross items 1-10 118135

337

Appendix 2: Variable cost (Rs. ha-1) (Experiment 1)

P: planting density; B: Boron; MC: Mepiquat chloride

Treatments Seed cost Cost of

MC

MC application

cost

Cost of B B application

cost

Payment to

pickers

Total variable

cost

P = 25 cm Control 2250 0 0 0 0 9423 11673 600 ppm B 2250 0 0 250 175 10331 13006 1200 ppm B 2250 0 0 500 175 10106 13031 MC at squaring 2250 515 175 0 0 10208 13148 MC at flowering 2250 600 175 0 0 9996 13021

600 ppm B + MC at squaring 2250 515 175 250 175 11906 15270 600 ppm B + MC at flowering 2250 600 175 250 175 10952 14402 1200 ppm B + MC at squaring 2250 515 175 500 175 12226 15840 1200 ppm B + MC at flowering 2250 600 175 500 175 11630 15330

P = 15 cm Control 3750 0 0 0 0 10460 14210 600 ppm B 3750 0 0 250 175 11118 15293 1200 ppm B 3750 0 0 500 175 11552 15977 MC at squaring 3750 515 175 0 0 11552 15991 MC at flowering 3750 600 175 0 0 11185 15710 600 ppm B + MC at squaring 3750 515 175 250 175 12459 17324 600 ppm B + MC at flowering 3750 600 175 250 175 11788 16738

1200 ppm B + MC at squaring 3750 515 175 500 175 14117 19231 1200 ppm B + MC at flowering 3750 600 175 500 175 13316 18516

338

Appendix 3: Fixed cost (Rs. ha-1) (Experiment 2)

Sr.

No.

Operation/input No./Amount/Q

uantity per ha

Rate/unit (Rs.) Cost/ha (Rs.)

1 Sowing operations

1.1 Land preparation charges

Deep ploughing 1 3400 3400

Ploughing/cultivation 3 1475 4425

Planking 2 750 1500

Leveling 1 1700 1700

Sub total (a) 11025

2 Seed and sowing operations

2.1 Seed

Seed (kg)+delinting cost+seed treatment 15 kg 135 2025

Sub total (b) 2025

2.2 Bed Planting

Bed shaper 1 3000 3000

Sowing via dibbling method 3 man days 400 1200

Sub total (c) 4200

3 Fertilizer cost

3.1 Fertilizer (bags)

Urea 6.6 1850 12210

DAP 5.21 3750 19537.5

SOP 3 2370 7110

3.2 Transportation charges (fertilizer) 14.81 20/bag 296.2

3.3 Application charges (man days) 1 400 400

Sub total (d) 39554

4 Irrigation

4.1 Canal water charges (abiana/ha) - - 239

4.2 Private tubewell (rate/hour Rs. 310) per

irrigation 2325 2 irrigations 2325/ha 4650

Sub total (e) 4889

5 Labour for irrigation

Water course cleaning and application

charges(man days)

3 man days

400 1200

Sub total (f) 1200

6 Interculture/hoeing

Manual weeding/thinning (man days) 10 man days 400 4000

Sub total (g) 4000

7 Plant protection including application (Weedicides + insecticides)

Glyphosate 1.5 L 950/L 1425

Imidachloprid 625 ml 1000/L 625

Acetamaprid 625 g 450/250 g 1125

Emamectin 500 ml 650/500 ml 650

Application charges (man days) 2 man days 400 800

Sub total (h) 4625

Grand total (a-h) 71518

8 Mark up on investment @ 9% per

annum on items for 8 months

(excluding water rate 3.1)

44626

-

4016

9 Land rent for 8 months @ Rs. 62500

per anum

8 months

5208

41664

10 Agricultural Income Tax for 8 months

-

-

162

11 Management Charges for 8 months @

Rs. 14000/month for 100 Acres

8 months

350

2800

Gross items 1-10 120160

339

Appendix 4: Variable cost (Rs. ha-1) (Experiment 2)

B: Boron; MC: Mepiquat chloride

Treatments Cost of MC MC application

cost

Cost of B B application

cost

Payment to

pickers

Total

variable

cost

Control 0 0 0 0 9164 9164 1 kg B ha-1 0 0 1176 0 9642 10818 1.5 kg B ha-1 0 0 1764 0 9904 11668 2 kg B ha-1 0 0 2352 0 10189 12541 2.5 kg B ha-1 0 0 2940 0 10116 13056

MC at squaring 515 175 0 0 10037 10727 MC at flowering 600 175 0 0 9709 10484 MC at squaring + 1 kg B ha-1 515 175 1176 0 10312 12178 MC at flowering + 1 kg B ha-1 600 175 1176 0 10029 11980 MC at squaring + 1.5 kg B ha-1 515 175 1764 0 10993 13447 MC at flowering + 1.5 kg B ha-1 600 175 1764 0 10457 12996 MC at squaring + 2 kg B ha-1 515 175 2352 0 11817 14859

MC at flowering + 2 kg B ha-1 600 175 2352 0 11309 14436 MC at squaring + 2.5 kg B ha-1 515 175 2940 0 12529 16159 MC at flowering + 2.5 kg B ha-1 600 175 2940 0 11928 15643

Documents

IMPROVING COTTON PRODUCTIVITY BY PLANT ...prr.hec.gov.pk/jspui/bitstream/123456789/8035/1/Ali...2018/11/01 · Ali Zohaib 2007-ag-2489 ii To The Controller of Examinations, University