TOPIC: PHYSIOLOGICAL CHANGES IN PLANTS DURING MOISTURE STRESS CONDITION
PRESENTED BY ZUBY GOHAR ANSARI
TAM/14/26
INTRODUCTION WHAT DO YOU MEAN BY
PHYSIOLOGICAL CHANGES:
EFFECTS OF WATER DEFICITS ON PHYSIOLOGICAL, MORPHOLOGICAL AND BIOLOGICAL PROCESSES
1. Water deficit at cellular leveli. Cell Division: It is less affected as compared to
cell elongation.ii. Ex. Radish leaves DNA content reduced to 40%
of control leaves at W.P. of -2 bars and to 20% at -8 bar.
iii. Cell Enlargement: Reduction in T.P. causes in cell enlargement, which in turn decreases root and shoot elongation.
iv. Also interferes with stomatal opening.
2. Leaf Expansion : In maize, rate of leaf enlargement is greatest when leaf water potential is in the range -1.5 to -2.5 bars.
As leaf water potential falls to -9 to -10 bars, leaf elongation vertically ceases, photosy. Was slightly impaired.
3. Turgor: Lag in absorption behind transpiration → loss in turgor → due to rise in transpiration→ due to increase in atmospheric dryness with onset of drought.
4. Plant structures: Leaf area, cell size & intercellular volume are
usually decreased. Cutinization, hairiness, stomatal frequency and
thickness of both palisade layers increased.
5. Root development: It is affected by soil water potential in a number of ways
In G’nut & wheat wt. of root decreased but number of root is same approx.
Roots grow towards water in the soil.
6. Photosynthesis: Water stress can reduced photosy.by
Reduction in leaf area Closure of stomata Reduction in activity of dehydrated
protoplasmic machinery Reduce photosyn. surface
Reduce the production of dry matter The leaf water potential at which stomata
close varies withA. Position of the leafB. Leaf ageC. Growth conditionD. Rate of stress
7. Respiration: It increases in early stage afterwards decreases as it is severe.
Severe dehydration of tissues caused a burst of respiration in some species results of hydrolysis of starch to sugars
In general reduction in photosynthesis, commences W.P. commences to zero.
It decline more or less turgor pressure to a value of zero.
8.Distribution of assimilates: Distribution pathway is highly resistant to water stress.
Velocity of assimilatory movement was influenced by water stress as low as -30 bars in wheat.
Effect of water deficit distribution of assimilates to various plant organs will depends on
I. Stage & development of plantsII. Pre-history of stressIII. Degree of stressIV. Degree of sensitivity to stress of organs
9.Photorespiration: It is unaffected by short term stress in certain conditions but substrate for photorespiration depleted.
10.Protoplasmic effects of water deficit: Removal of water surrounding protein molecules may cause changes in configuration affecting permeability, hydration, viscosity & enzyme activity.
11. Carbohydrate metabolism: In cotton as a result of stress, the sugar content increases & starch content decreases.
By contrast, in stems, the conc. Of both sugars and starch increases indicating reduced water supply not only affects photosynthesis but also the ability of plants to utilize the products of photosyn.is still more impaired.
12. Enzyme activity: In maize increase in water stress cause nitrate reductase activity decline at much greater rate than peroxidase activity.
Levels of enzymes involving hydrolysis and degradation usually either remains same or increase.
13. Nitrogen metabolism: Hydrolysis of proteins occur in wilted plants is accompanied by increased amino acids.
Synthesis of RNA & proteins are decreased in sugar beet before visible wilting occurs.
14. Nucleic acid: its synthesis is unaffected by moderate stress in older leaves, but Rnase activity increases which degrade RNA.
Reduced growth of stressed seedling due to alternation of nucleotide composition Of the RNA.
15. Ageing: It produces changes in the course of protein synthesis and water stress greatly accelerate the change normally associated with senescence.
16. Growth regulators: A. ABA: In water stress plants , ABA
synthesized and released from mesophyll to chloroplast and travels to guard cells where it
a. Inhibit K+ uptake b. Inhibit H+ releasec. Promote leakage of malate from guard cells. These effects cause guard cells to lose
turgor. Loss of turgor decreases stomatal aperture.
B. Cytokinins: In stressed sunflower plants, cytokinin content in root exudates was reduced.
In detached lettuce leaves, water stress had the effects of decreasing cytokinin as ABA increased.
C. Gibberellins: GA declined in tomato shoot, root following stress applied by flooding roots.
D. Auxins: IAA in sorghum leaves decreased as a result of water stress.
Water stress can directly affect the action of IAA in shoots.
E. Ethylene: In cotton plants, water stress induced abscission of leaves that is promoted by plants.
Water stress in cotton, bean plants, ethylene level are elevated rapidly in both leaves and petioles.
17.Reproductive and grain development:
A. flowering: Moisture regimes during this period largely determines the no. of fruits which will be produced.
B. Fruit enlargement: Severe stress during this period results in small or shriveled grains.
C. Ripening: Water stress has no effect on yield component but may effect length of ripening period.
18. Crop yield: Effect of water stress on yield depends on stage at which it occurs.
At early stage, no. of primordial branches may be reduced.
Drastic effect of stress was observed at flowering stage.
EFFECTS ON CEREALSOn floral initiation, anthesis
(wheat& rice).At ripening stage (reduc. in test
wt.).Plant height, leaf area.Leaf rolling, drying, premature
death of leaf.Reduc. in photosyn. & dry matter
production.
EFFECTS ON PULSES & FRUIT CROPS• Flower abortion .• Stress during pod filling reduces test
weight.
• In fruits, shedding of fruits. Ex. June drop of apples & citrus.
• In some cases, drought prevails causes premature flowering which results in reduced yield, size of pods, seeds & fruits.
MOST SENSITIVE STAGES OF MAJOR CROPS 1. Rice: panicle initiation, flag leaf & milky 2. Sorghum: booting & flowering 3. Maize: tasseling & silking 4. Groundnut: peg penetration & pod
development 5. Sunflower: head formation and early grain
forming 6. Pearl millet: booting & flowering 7. Finger millet: flowering 8. Soybean: flowering & pod filling 9. Cotton : square formation & boll development 10. Black & Green gram: flow. & early pod
develop.
EFFECTS OF STRESS IN MAIZETasseling and silking stage ( most
harmful) , grain filling reduc. yield drastically than at vegetative stage.
Pollen develop. slower leads to reduc. fertility → reduc. in grain no. wt. per ear.
During anthesis shorten duration of grain filling by causing premature desiccation of endosperm & by limiting embryo volume.
EFFECT OF WATER STRESS IN SUNFLOWERDrought tolerant cropDeeper root system → due to stress
at veg. stageYield and oil content decreases Interesting fact 1. under normal cond. Oil content
and seed is high than seed protein content.
2. In mild stress cond. Seed protein content high in hybrids than that of oil content.
EFFECTS OF WATER IN SOYBEAN Leaf expansion rate reduced Leaf flipping movement seen Water stress causes early flowering &
reproductive growth Leaf clampingEffect of water stress in groundnut:
Fairly drought tolerant Low rainfall, prolonged dry spell decrease its yield Photosyn. , carbohy. ,chlorophyll , enzymatic
activity ,internodal length , pod & kernel development reduced.
EFFECTS OF WATER STRESS IN COTTONo Affect both production & distribution of
carbohydrates.o Reduction of leaf area o Mummified dry bolls ( younger bolls)o Older bolls size reducedo Stress during peak flowering and early pod
develop. reduced yield
GROWTH STAGES
REDUCTION IN YIELD WITH ONE
DAY OF STRESS(Kg lint/ha)
Squaring 9.2
Peak flowering 18.8
Late flowering 16.1
Boll maturation 3.6
Hearn and Constable 1984
METHODS FOR MITIGATE ADVERSE CONDITIONS OF WATER STRESS IN CROPS 1. RICE: a) Seed hardening KCl 1% with CCC 50 ppm &
foliar spray of 1000ppm CCC → increased grain yield up to 5723 kg/ha
b) Foliar spray of murate of potash 2% at flower initiation → 400 kg/ha
c) Foliar spray of 0.3 ppm of brassinolide at panicle initiation and flowering → 605t/ha
2. SORGHUM : kaolin 3% foliar spray → 10%
3.RAGI: Seeds treated with CCC 5 ppm → 12%
4. BAJRA: Combined spray of 0.5% ZnSO4 & 0.5% CuSO4 together with boric acid 0.2% → 16.8%
Soaking Bajra seed with 2% KCl or NaCl for 16 hrs → 329 kg/ha
5.SOYBEAN: Kaolin 3% or liquid paraffin at 1% as foliar spray → 10%
Foliar spray of salicylic acid 100 mg/lit on 30 & 45 DAS → 16%
6.BLACKGRAM: Foliar spray of KCl at 0.5% during flowering → 100 kg/ha
7.SESAMUM: KCl 0.5% spray at flowering & capsule maturity phase → 1204 kg/ha
8.GROUNDNUT: Foliar spray of KCl 0.5% → 10%
9. COTTON: Foliar spray of kaolin 3% & liquid paraffin 1% spray → 27.4%
BENEFICIAL EFFECTS OF WATER STRESS
1.Moderate water stress improved the quality of Apples, Pears, Peaches and Plums.
2.Water stress increases the alkaloid content in datura.
3.Water stress increases the percentage of oil in soybean but decreases the yield of oil per acre.
4.Protein content of wheat increased by water stress during maturation.
5. Although water stress decreases total vegetative growth , it generally increases the rubber content in rubber plants.
WATER STRESS IN RELATION TO DISEASES AND INSECT RESISTANCE 1. Development of bark cankers is
usually correlated with decreased water content of the bark.
2.The incidence of blossom end rot of tomato fruits is said to be higher on plants subjected to severe water stress.
3. Trees with low water stress have high oleoresin exudation pressures, which seems to be unfavorable to the establishment of beetles.
CASE STUDIES
RHIZOBIAL INTERACTION WITH WHEAT UNDER WATER STRESS(GROWTH AND NITROGEN ASSIMILATION UNDER STRESS AND NORMAL CONDITION)
TREATMENTS
WATER STRESS
NORMAL
WATER CONDITION
YIELD (g/pod) YIELD (g/pod)GRAIN STRAW BIOLOG
ICALGRAIN STRAW BIOLOGICAL
UNINOCULATED
2.4 5.6 8.0 8.1 10.1 18.2
Os 4 2.7 5.6 8.3 8.6 12.4 21.0Ew24 3.6 5.8 9.4 11.1 14.0 25.111a 5.1 8.3 13.4 14.4 17.8 32.2
17bt 5.0 8.4 13.4 12.1 14.8 26.9M 10 4.8 9.1 13.9 11.3 12.3 23.6Os 2 6.3 8.4 14.7 7.2 13.2 20.4SEm± 0.2 0.4 0.3 0.5 0.7 0.3C.D.(0.05)
0.7 1.2 0.7 23.9 25.1 6.8
TREATMENTS
WATER STRESS NORMAL
WATER CONDITION
NITROGEN
(mg/pot) NITROGEN
(mg/pot)
GRAIN STRAW TOTAL GRAIN STRAW TOTALUNINOCULATED
62.0 59.0 121.0 182.0 72.0 254.0
Os 4 71.0 23.0 94.0 202.0 69.0 271.0Ew24 93.0 40.0 133.0 250.0 107.0 357.011a 124.0 51.0 175.0 252.0 85.0 337.017bt 150.0 87.0 237.0 263.0 96.0 359.0M 10 132.0 81.0 213.0 260.0 71.0 331.0Os 2 162.0 53.0 216.0 207.0 73.0 280.0SEm± 6.4 5.8 4.4 11.9 4.0 8.7C.D.(0.05)
18.5 16.8 12.7 25.8 24.6 13.7
Indian journal of plant phy.(april-june,1997) Sangeeta paul IARI newdelhi
LEAF EXPANSION IN BRASSICA SPECIES IN RESPONSE TO WATER STRESS (LEAF WATER POTENTIAL,R.W.C. , & SOLUTE POTENTIAL AT ZERO TURGOR IN BRASSICA SPECIES)
SPS./STRESS TREATMENT
LEAF W.P.(MPa)
R.W.C. S.P AT ZERO T.P.(MPa)
BEFORE STRESS PERIODB.juncea -0.45 0.81 -1.01B.napus -0.64 0.94 -1.32
END OF STRESS PERIODB.J Control -0.89 0.78 -1.14Stressed -1.33 0.74 -1.49
B.N Control -0.98 0.81 -1.24Stressed -1.58 0.69 -1.57AFTER REWATERING, TWENTY FOUR HOURS
B.J Control -0.85 0.76 -1.20Stressed -1.14 0.72 -1.38
B.N Control -0.90 0.81 -1.27Stressed -1.24 0.74 -1.50
EFFECT OF WATER& RECOVERY ON LEAF AREA (CM SQUARE/PLANT)
SPECIES STRESS PERIOD RECOVERY PERIOD
CONTROL STRESSED CONTROL STRESSED
B. juncea 135.0 106.8 149.4 125.2
B.napus 81.5 70.2 102.5 81.0
A.KUMAR & J.ELSTON
EFFECT OF WATER STRESS ON PHOTOSYNTHESIS AND WATER RELATIONS OF WHEAT VARIETIES (EFFECT OF WATER STRESS ON STOMATAL RESISTANCE & PHOTOSYNTHESISOF WHEAT VARIETIES)
VARIETY
TREATMENT
STOMATAL RESISTANC
E
(S/cm invers
e)
NET PHOTOSYN.
(P net)
(µl CO2
per m sq. sec
inverse
T.S. A.S. S.D.S. T.S. A.S. S.D.S.
C-306 Control 1.32 2.97 2.63 10.86 15.54 6.18
Drought
2.17 4.34 8.16 9.74 11.66 4.64
Reirrigated
1.40 3.10 3.08 11.30 14.02 6.00
Kalyansona
Control 1.14 2.58 2.91 13.56 16.58 8.02
Drought
1.33 3.2 8.53 5.70 7.84 3.14
Reirrigated
1.18 2.87 3.16 13.62 13.62 8.20D.C.Uprety and G.S. Sirohi, IARI New Delhi
PHYSIOLOGICAL AND BIOCHEMICAL CHANGES IN CLUSTER BEAN ( CYAMOPSIS TETRAGONOLOBA L.) GENOTYPES UNDER WATER STRESS
VARIETIES Stem
CONTROL
Leaf Seed
HG-75 1.841 1.951 1.738 2.271 0.675 0.573
IC-11521 1.894 1.500 2.044 1.379 0.864 0.483
DURGAJAY
2.357 2.820 2.234 2.987 1.097 1.172
FS-277 1.466 1.763 1.594 2.034 0.927 0.643
19-1-55 2.079 1.637 1.445 1.623 0.902 0.920
CONTROL STRESS CONTROL STRESSSTRESS
EFFECT OF WATER STRESS ON DRY WEIGHT OF STEM,LEAF,SEEDS IN FIVE GUAR VAR.AT HARVEST.(CLUSTER BEAN) (g/plant)
SOURCE: INDIAN JOURNAL OF PLANT PHYSIOLOGY M.S Kuhad and I.S Sheoran
VARIETIES
PROLINE
CONTROL
STRESS
SOLUBLE SUGARS
CONTROL
STRESS STARCH
CONTROL
STRESS
HG-75 2.371 12.180 7.702 8.282 17.55 6.536
IC-11521 2.880 8.307 8.400 7.792 19.260 7.373
DURGAJAY
2.430 6.360 7.333 5.527 27.027 3.829
FS-277 3.003 6.598 9.282 8.002 15.652 8.073
I9-1-55 4.300 9.520 9.890 8.882 28.129 22.440
RESPONSE OF AVENA SPECIES LEAF PHOTOSYNTHESIS AND STOMATAL CONDUCTANCE TO WATER STRESS (RATIO OF PHOTOSYNTHESIS(Pn) & STOMATAL CONDUCTANCE (gs) OF OAT SPECIES IN RESPONSE TO WATER STRESS AT VEGETATIVE AND FLOWERING STAGES OF CROP GROWTH.
SPECIES
PHOTOSY.
µMol(co2)
/m sq. sec inv.
S.C. (mmole / m sq.
Sec inverse)
Veg. Flo. Veg. Flo.Cont. Stress Cont. Stress Cont. Stress Cont. Stress
A.stri. 24.00 13.71 25.56 14.80 0.523 0.217 0.669 0.324A.bre. 20.02 13.06 27.16 12.76 0.344 0.187 0.632 0.261A.vavi.
26.17 12.88 28.78 13.16 0.636 0.215 0.742 0.342
A.abs. 22.91 10.46 19.47 12.95 0.493 0.192 0.564 0.264A.sat. 27.97 14.12 28.35 16.37 0.637 0.258 0.864 0.456A.mar. 21.32 11.16 24.61 13.21 0.564 0.219 0.712 0.432A.ste. 19.62 9.42 22.42 10.69 0.514 0.202 0.676 0.324CD at 5%Spe.(S)
1.68 0.79 0.06 0.03
Tre.(T) 0.90 0.42 0.03 0.01SxT 2.38 1.12 0.08 0.04
EFFECT OF ETHEREL ON SOME MORPHOLOGICAL & BIOCHEMICAL PARAMETERS IN SOYABEAN GERMINATING UNDER MOISTURE STRESS ( EFFECT OF MOISTURE STRESS ON GERMINATION, VIGOUR INDEX & GERMINATION RELATIVE INDEX)
TREATMENT STRESS LEVEL
GERMINATION% (TRANSFORMED)
VIGOUR INDEX (VI)
GERMINATIONRELATIVE INDEX
CONTROL 0 73.3 5644.10 20.00.4 53.3 2531.75 13.31.0 26.7 931.0 5.03.0 6.6 112.2 3.05.0 - - -
ETHREAL 0 86.6 11431.2 240.4 60.0 2940.0 191.0 26.6 984.2 73.0 26.6 604.4 35.0 - - -
CD at 5% level of significance
- 1.39 193 1.98
SOURCE: INDIAN JOURNAL OF PLANT PHYSIOLOGY Rajinder Sharma and Mohinder K. Grewal