Screening for qualitative and quantitative status of green tea inten clonal agro-types. cultured at BTRISS, ODAHLEA,Bangladesh.

Muhammad A M Chowdhury and Kazi M. M. AlamDepartment ofBotany, University ofChittagong

Cbittagong~331,BangJadesh

Key words:, Biomass, caffeine, clonal agro-types, pigments, poly-phenol, nutrients, yield Potential

Summary: Yield potential in terms of quality of pluckable twig nos, twig biomass and quantitative status 0:

some bio-chemicals (photo-synthetically active pigments, nutrients- viz. N.P.K. Ca and Na, caffeine and poly·phenol) of green tea in ten clonal agro-types- viz.TVl and BTl-BT9, of 15 years old tea plants cultured undesame agro-climatic conditions at BTRISS, Odablea, were studied along with soil on three plucking periods (vizincreasing, peak and decreasing) in one full tea year to screen out the gape of knowledge in the production aD(

improvement of status of Bangladesh tea in world market Some physico-chemical properties of soil such 3!

SMC, OM, pH, Be, CEC, N, P, K, Ca and Na were studied on three plucking period and the results showed tba­the soil was sandy-clay loam, acidic and infertile. Yield potential of pluckable twig number and biomass rangecfrom 1455-1800 no. p..l yr-l. 876-1176 g (fw) p-l yr.1 and 176-249g (dw) p-l yr..l respectively Average values 0:

both twig nos. and biomass were maximum in peak and mininmm in decreasing period. Whilst average value 0:

pigments content ranged form 1038-1411 J.Lg g-1 and did not show any significant value either "with agro-types 0]

plucking periods. Highest average values of twig N, P, K, Ca and Na content varied from 47818-60880, 1666-2270, 14713-21640, 11056-14500 and 710-1186 J.Lg g-1 respectively.Twig N, P, K and Na contents wenmaximum in peak and P and Ca content were maximum in increasing period. Caffeine content varied fron27566-37386 ~-land maximum caffeine content was measured in increasing period. Twig poly-phenol contenvaried from 117890-211386 ....g g-l and maximum value was obtained in peak period in each clonal agro-typeThe present study concludes tbat yield potential of pluckable twig biomass, photo-synthetically active pigmentsnutrients, caffeine and poly-phenol contents of green tea in ten clonal agro-types varied with agro-types as weI:as plucking periods and can be ranked superior in the order of TV} for yield, BT9 for pigments, BT2 for nutrienuand caffeine, and BT7 for poly-phenol contents.

Introduction:Tea is undoubtedly recognized as the worlds most popular beverage other than water (Stagg andMillin, 1975). Tea is the most popular drink of Bangladesh and it has been growing in Bangladesh since 1854.Nowadays tea has become one of the most dynamic agro-export industrial products of Bangladesh and plays avital role in its economy. One hundred and fifty eight tea estates consisting of 48,571 hector of land have beenestablished in the north-and so11theastem regions of Bangladesh. About 44.7 hector of lands have productive teaplants of mixed varieties of seedlings i.e,Cbina, Manipuri, Assam, Burma and Hybrid- clones (BTI-BTIl) alongwith clones of Toldai of India. The rest of the land of tea estates is- either abandoned or left unused. Thoughhybrid clones have become most popular for their commercial values such as high yield and excellent quality forboth flavor and colour yet hybrid clones bave occupied only 10 percent of total tea plantation. Most of the teaestates have already given up the plantation of seedlings varieties for their pOOr yield and low quality.The yieldpotential in terms of quality and quantity of clonal agro-types of Bangladesh tea have been found to be superiorover the existing traditional seedlings ones. It is reported that the demand of Bangladesh black tea has beenincreasing both for export and home consumption. But the annual production of Bangladesh tea has never beenincreased beyond 4.7 million kg from the existing plantation of tea estates. In the last 5 years, the production oftea has been tremendously decreasing which has been found to decrease the annual export quantity by keepingconstant the supply of increasing demand by 3.2 percent to the local needs. It has badly affected the face valueas well as the future prospects of Bangladesh black tea in addition to the earning of foreign currency byexporting the ever-demanding Bangladesh tea to more than 17 coWltries of the world.So far the literature review are concerned, BTRI has done considerable of research works on the use andmanagement of soil, tea improvement, crop management, pest management, tea bio-ehemistry, tea processingand tea assessment But no research on qualitative yield potential ofpluckable twig no., twig biomass (fresh wt.and dry wt.)~ quantitative estimation of photo-synthetically active pigments, nutrients, caffeine and poly-phenolstatus of twig of above clonal agro-types cultured under the same agro-climatic condition on three pluckingseason (i.e.increasing, peak and decreasing) in a full tea year have yet been undertaken where it bas beenconsidered and felt utmost necessary as ever demanding phenomenon by the concerned Ministries, NGO'sagencies and Private sectors to fill up the gap of knowledge in the improvement of status of Bangladesh tea inthe world perspective. Moreover, more plantation of hybrid-elones in unused and abandoned tea estates ofBangladesh are worth consideration for maximjzing the yield potential of high quality green as well as black teafor export and home consumption. Otherwise, earning of foreign currency as cash crop will be reducing belowthe target level in near future. .

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With this view in mind, an intensive and extensive research on some major compamble factors of bothqualitative and quantitative status of pluckable green tea was carried out during three plucking periods in a fulltea year in an experimental site of ten clonal agro-type of fifteen years old at BTRISS, Chittagong to screen outthe knowledge in the production and improvement of status ofBangladesh tea in World perspective.

Materials and methods: An experimental site namely section-7 with ten clonal agro-types (viz. TV1 and BTI ­

BT9) of tea -Camellia sinensis (L.) O.kuntze, cultured in 1985 was selected for the present study. The study siteis situated about 50-52 m high from the sea level at altitude of 20°40'-20042' N and latitude of 92°4'-92°6' E onthe eastern hilly side near the coast of Bay of Bengal. The area embraces mean annual minfall, temperature,relative humidity and light intensity of 3200mm,2SoC,90% and 3200 lux respectively. There is a clear variationof six season in a year with marked change in climate and soil. The experimental site receives partial shade offour species of legumes namely Indigofera tismannia and Derris robusta of Papilionaceae, Acaciaauricau/ifiJrmis and A/bizzia procera of Mimosaceae and Pe/tiph/orum inerme of Caesalpinaceae which wereplanted at about 5m distance from each other. The experiment was designed in an area of 2 hector on CRDmethod and the site was divided in to 5 stands. Each stand consisted of two agro-type and each agro-typecomprised of twelve row of fifty plant. The whole site is situated in the valley of hills with good drainagecondition. The whole tea year was divided into three plucking period viz. increasing (May-July), peak (Aug.­Oct.) and decreasing (Nov.-Jan.) (Muttalib-per. corom. 2000).Soil sample from each stand were collected in triplicate using soil augar from two different depth such as topsoil (1-25cm) and sub soil (26-5Ocm) on early monsoon, monsoon and late monsoon (Chowdhury and Rahman,1991,1994). All sieved soil samples were dried in oven at 105°C for 72 hours and used to determine majorphysicochemical properties (viz. ST, OC, OM, pH, EC, CEe, N, P, K,Ca and Na) except that of SMC where itwas determined after 72 hour of rainfall gravimetrically (Mism,1968).Soil texture was determined byBouyoucus Hydrometer Method and named after soil texture class triangled (USDA,1951).Soil OC and OMwere determined by Wet-oxidation Method (Walkley and Black,1934).pH and EC were determined based on 1:2 soil and water suspension using ca1ibmted digital pH meter andconductivity meter respectively. CEC was extracted with 1M KCI and determined by Micro-KjeldahlDistillation Method (Jackson,1973).Total N was extracted with mixed catalyst (H2S04+CuS04) and determinedby Micro-Kjeldahl Distillation Method (Jackson,1958).Available P,K,Ca and Na were extracted with 1Mammonium acetate-NRtOAC. Soil P was determined Spectrophotometrical1y (Blue Colour Method-Jackson,1958) andK,Ca and Na were measured by Flame Photometer Method (Jackson,1958).Ten plants of each clonal agro-type were earmarked mndomly from each stand to collect twig sample (two leafand one bud) for determining the quality of twig (no. and biomass) and quantitative status of some bio­chemicals (viz. photosynthetically active pigments-PP, nutrient-N,P,K,Ca,Na, caffeine-Cfn and poly-phenol-ppl)of green tea in a full tea year during 2000.Twig biomass was assessed on weekly basis in medium pruned bushby harvest method (Chowdhury and Rahman, 1991,1994). Photosynthetically active pigments (Chlorophyll a,band carotene ) of freshly plucked twig (second leaf) were extracted with extra pure acetone and determinedSpectrophotometrically (Wettestein,1957). Nutrients (viz. N,P,K,Ca and Na) were extracted with sulfuric­peroxide (H2804+H202) digestion mixture and determined by standard method (Allem et al.1986). Twigcaffeine contents were determined by Chloroform Method (Annon-BDSS,1975) and poly-phenol content wasestimated by Spectrophotometer Method (Molla,1981; Cbaudhury,1993;Alam,2000).Statistical analyses were done according to student's t-test and the calculation of CVOIO was as (SD/Meanvalue)xl00.

Results: The result as shown in Table-I reveal that physico-chemcial properties of soils of study area changedwith profiles, stands and seasons. But the variations were not remarkable ones.The average value of moisturecontent, organic carbon, organic matter, electrical conductivity, cation exchange capacity and pH were found tobe 12%, 0.50/0, 90/0, 155 J.LScm), 7 meq g.I and 5 on early monsoon and 15%.0.50/0, 0.9010, 69 )J.Scm-l,7 meqg­1, and 5.5 on late monsoon respectively. The average value of nutrients such as total N, available P, K, Ca andNa were found to be 810, 10, 11, 33 and 33 J.Lg g-1 on early monsoon and 714, 9, 13, 43 and 35 J.1g g_l on latemonsoon respectively. In general, the soil was found to be sandy clay loam, acidic and infertile. The calculatedCVOIO for any studied parameters did not exceed beyond 14% except that of EC where it was found to be39010.Yield potential in tenus oftwig number per plant per week were found to vary with agro-types and periods.Twig number varied from 47 (BTs) to 59 (TVt ), 53 (BT4,BTg) to 64 (TVt) and 33 (BT) to 48 (BT,) onincreasing, peak and decreasing periods respectively. The average value of twig number (average of threeplucking periods) was found to be maximum in TV1 (56 p-l w_1

) and minimum in BT9 (45 p-l w_1). Pluckable

twig biomass (fresh wt) varied from 284g p-1S·l (BT6) to 431 g p-1s-l(BT9)" 361g p-1s-I(BT9) to 463g p-IS-l(TV\), 293 g p-\s-\ (TV\) to 349 g p-1S-l (BTg) on increasing,~ and decreasing period respectively. In thesame way., pluckable twig biomass (dry wt) varied from 54 gp- s-I(BTg) to 86 g p-lS-l (BT9), 73 g p-l s-l(BTg) to86g p-l s·I(BT9) and 40 g p-1S·l(BT3) to 71g p-1s-l(TVt) on increasing, peak and decreasing periods respectively.

Session II -42-

Total pluckable twig biomass per plant per year (fresh wt) was found to be maximum in TV! (1176 g p-l y.l )and minimum in BTl (876 g p-l y.l ), while the pluckable twig biomass (dry wt) was found to be maximum inTV) (249 g p-) y.l) and minimum in BTg (177 gp.l y.l ). Figure-l shows that number of pluckable twig and twigbio~ were found to be maximum on peak period and minimum on decreasing period in each clonal agro­type. ANOVA of pluckable twig biomass (fresh and dry wt) did not show any significant value with agro-typesbut showed significant value with plucking periods (fable-2).

The results as shown in figure-2 exhibit that photosynthetically active pigments content of twig of each clonalagro-types was found to be more or less the same but changed with plucking periods. The highest average value(average of three plucking periods) was found to be 1411 Ilg g.l in BT9 and the lowest average value was foundto be 1039 Ilgg.J in TV! and showed the sequence as BT!Y'BTz>BT!>BTs>BT6>BTg>BT7>BT4>TV). ANOVAof total twig pigment contents did not show any significant value with agro-types and plucking periods (fable-2). -

Table 1: Cbange of pbysico-cbemical properties of soils on tbree plucking periods at BTRISS, Odablea.

Moisture EC OC OM CEC Total N Available nutrients «~g g-l )Period content Texture pH J.!Scm-! (%) (%) meqg-l (Ilg g-l ) P K Ca Na(%)

Increasing 11.45 SCL 4.83 158 0.51 0.88 7.25 810.7 9.90 10.60 33.40 33.10Peak 14.62 SCL 5.65 119.5 0.55 0.94 7.48 814.2 10.01 13.84 41.26 33.58Decreasing 13.65 SCL 5.47 68.5 0.49 0.84 6.77 714.1 7.86 13.26 42.80 34.85CV% 12.27 8.11 38.93 5.91 5.68 5.05 7.29 13.08 13.75 12.88 2.67Legend: Increasmg- Early monsoon; Peak- Monsoon; Decreasmg-Late monsoon. Each data IS the average mean

of three samples of nine replicates

1400 _ Fres h wt. ~Dtywt. -.tr-T..-ig no .lpIa.n 2000 250000 '--;!I;;-'P

1800 v, -+-Cfn.1200

1600 0>:> 200000- 1000 1400 ..

i -3'> ~-a 800 1200 to 150000... 1000

C: .... .!! .2.. 600 Q.

'" 800 0 E 100000E c: 1:0 400 600 <>I ()

:0 '3' 00> 400 I- m 50000'iii 200 200I- _."-

0 0 0

T~BTIBTIBnBnBnBnBTIBnBn T~ BTI BTI BT3 Bn BT5 BT6 BT7 BT8 BT9agrotype Agro type

Fig. 1: Change of twig no. and biomass of plucked Fig. 2: Cbange of photosynthetic pigments, nutrients,green tea in ten clonal agro-type cultured at BTRISS, caffeine and poly-phenols of green tea in ten clonal agro-Odablea, Cbittagong type cultured at BTRISS, Odablea, Chittagong

Table 2: Analysis of variance of pluckable twig biomass, pigments, nutrients, caffeine and poly-phenolstatus in green tea of ten agro-types and three plucking periods.

F-values

Source of Degree of Pluckable twig Total Twig nutrients TwigTwig

variance freedom biomass twig poly-Fresh wt. Drywt. pigments N P K Ca Na

caffeinephenol

Varieties 10-1=9 1.22 NS 1.14NS 1.54 NS *5.53 **3.14 1.05NS **2.47 1.15 *5.15 0.55P. periods 3-1=2 **7.54 **5.35 1.38 NS *34.69 **3.94 *8.58 2.85NS 1.27 **40.5 **47.87Error 29-11=18 -- -- -- -- -- -- -- -- -- --Legend: * denotes SIgnificant at 5% level, ** denotes Significant at 1% level and NS= non SIgnificant.

Twig nutrient status were found to change with agro-types and periods. N content ranged from 43330 (BTg) to57610 (BTz), 60700 (BT4) to 75110 (BT2) and 37730 (BT7) to 49920 j.I.g g.J (BT2); P content ranged from 1940(BTs) to 2410 (BTg), 1240 (BTs) to 2130 (BTg) and 1810 (BTl, BT4) to 2270 J.tg g.J (BTs); K content ranged

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from 17180 (BTl) to 23920 (BTs), 17390 (BT6) to 29330 (BTs) and 8590 (BT6) to 13130 J18 gJ (BT3); Cacontent nmged from 12000 (BTs, BT9) to 17670 (BTl) , 9830 (BTs) to 13000 (TV}) and 10500 (BTs) to 14670J.Lg g_l (lV1); Na content ranged from 680 (BT6) to 900 (BTs, BT,), 840 (BT6) to 1840 (BTs) and 580 (BT4) to920 J.Lg g_1 (BT7) on increasing, peak and decreasing period respectively. The highest average values ofN, P, Ie,Ca and Na contents (average of three plucking periods) were found to be 60880, 2270, 21640, 14500 and 1187J.Lg g.I in BT2, BTs, TV} and BTs respectively while the lowest average values were found to be 47487, 1667,14713, 11057 and 710 J.1g g} in BTs, BTs, BT6, BTs and BT6 respectively. Twig N, K. and Na contents werefound to be maximum on peak period and minimum on decreasing period but P and Ca contents were found tobe maximum on increasing period and minimum on peak period. ANOVA of twig N and P contents showedsignificant value with agro-types and plucking periods; twig K content showed significant value with pluckingperiods and twig Ca content showed significant value with agro-types only; but twig Na content did not showany significant value with agro-types and plucking periods (Table-2)..The results of figure-2 exhibits that twig eatJeine content was found to vary with agro-types and periods.Caffeine contents varied from 38670 (BT3) to 46670 (BT2), 25330 (BT4) to 38670 (BT2) and 17330 (BT}, BT3)

to 26670 J.1g g_1 (BT2,BT6) on increasing peak and decreasing period respectively. The highest average value ofcaffeine content (average of three plucking periods) was found to be 37337J.Lg g_1 in BT2 and the lowest valuewas found to be 27557 J.Lg g_l in BT3.Maximum eatJeine content was found on increasing period and minimumon decreasing period in each clonal agro-type. ANOVA of caffeine content showed significant value with bothagro-types s and plucking periods (Table-2).The result of Figure-2 also exhibit that twig poly-phenol content varied with ago-types and periods. It rangedfrom 207920 (BTs) to 235650 (BT4), 246040 (BTl) to 315350 (BT7) and 65840 (BT) to 107430tJg g_l(TVt) onincreasing peak and decreasing periods respectively. The highest average value of poly-phenol content (averageof three plucking periods) was found to be 211387 J.Lg g_1 in BT, and the lowest value was found to be 177890in ....g g_1 BTl. Maximum poly-phenol content was found on peak period and minimum on decreasing period ineach clonal agro-type. ANOVA of poly-phenol content showed significant value with plucking periods but didnot show any significant value with agro-types (Table-2).

Discussion: Choudhmy (1989) reported that some of the clwacteristics of good tea soils which are as follows:texture-sandy loam, organic eatbon-rich (2%), medium (1%), poor-below (1%), pH-4.5-5.8, total N- not lessthan 0.10/0, available P-I0J.Lg get, K-80J.Lg g..t and Ca-90J.Lg g_l respectively. The present experimental resultshows that the studied soil was sandy clay loam, acidic and infertile. Leaf composition and flushing pattern oftea have been observed to vary between clones (Rashid et al.,1980). Change in the environmental factors causeyield fluctuations in tea by affecting the growth rate of shoot (Tanton, 1981). In Bangladesh context, themaximum yield has been obtained at age group of21-30 years and there after it tended to decrease (Gazi, 1973).The results urge that the yield of studied clonal agro-types of 15 years old tea plants were found to vary withagro-types and periods, and possessed comparatively low yield Yet TV1 was found to be the superior for yieldMeanwhile, the difference of total· twig pigment contents among the agro-types and among the plucking periodswas poor i.e., the values were more or less the same. But BT9 was found to be the superior for pigments.Nutrient contents were found to vary with agro-types and periods. The results indicate that the studied clonalagro-types possessed low contents ofP and Na in comparison to N, K and Ca in the point ofoptimum range andBT2 was found to be the superior for nutrients. The satisfactory level of nitrogen content in first leaf is 5%(Willson,1975a). The usual range ofleafP is between 0.6 and 0.9% (Choudhmy, 1983); K Cone. below 1.7% infirst leafwith a bud and 1.6 % in third leafclearly indicate that K is limiting yield (Willson,1975b). Normal tealeaf as plucked contains an avemge of more than 0.5% Ca. (Eden,1976). Caffeine and poly-phenol contentswere also found to vary with agro-types and periods. The results show that BT2 and BT1 were found to be thesuperior for caffeine and poly-phenol contents respectively and the quantity of these elements were found to bereasonably high. Teas contain 1-5% of eatJeine and 15% of soluble poly-phenol (Cloughley,1981).The range ofcatJeine content in Bangladesh tea is 3-5% and that of poly-phenol is 22-31% (Choudhury,199O). The values ofmost nutrients, eatJeine and poly-phenol are comparable with the previous findings. Besides the elements arefound to vary iorespect to agro-types of tea, geographical origin, environmental conditions and agronomicsituation (Stagg and Millin,197S).The present study concludes that pluckable twig biomass, photosyntheticallyactive pigments,nutrients,caffeine and poly-phenol status of green tea in ten clonal agro-type varied with agro­types and plucking periods and can screen out as superior in the order of TV1,for yield potential,BT2 fornutrients and eatJeine and BT7 for poly-phenol contents.

AcknowledgeDleDt: The authors wish to thank Dr MK Huda for computing the data in prepuing the graph; toMllI Chowdhmy for typing the manuscript; to Mrs. Rowshon Ara for her suggestions and careful reading of themanuscrilt; to Prof. M Hirobe, Chairperson, organizing committee, leOS, 2001, for granting a research grant;to Bangladesh University Gnmts Commission for financial assistance and to the University of Chittagong forpermission and a travel grant to cover the expanses in attending the conference.

Session n -44-

References:AIam, K.M.M. 2000.Screening for pluckable twig biomass, pigments, nutrients, caffeine, poly-phenol and

1IIItrient cycling pattem in tea clonal agro-types oftea cultured at BTRISS, Odahlea. Chittagong.MSc.Thesis, Dept ofBotany, University ofChittagong.

ADem, s. E.~Grimsbaw,H.M and Rowland, A. P. 1986. Chemical Analysis In: Methods in Plant Ecology.Moore, P. D. and Chapman S.B. (Eds.) Second Edition Blackwell Scientific Publication.pp285-344.

Anon.197S. Determination ofCaffeine. Bangladesh Standard Specification. (BDSS) : 808-1974:20-21.Banu, D.RH., Rahman M.M and Chowdhury, M.AM. 2000. Studies on NPK and caffeine contents in

plucked twig tissues of five commercial agro-types of tea plants cultured at Odahlea, Chittagong.Bangladesh J. Life Sciences. (submitted).

Choudhury, M. A. 1990. Nutritional Properties ofTea. The Bangladesh Journal ofScientific Research, Specialissue: 45-54.

Choudhury, S.H. 1983. Nutrient requirements of tea plants (Camellia ~nensis L.) Ph.D. Thesis, ReadingUniversity, England

CItoudhury, S.H. 1989. Tea Growing,pp202.Choudhury,MAI993.Caffeine and poly-phenol contents in teas of Bangladesh and its nutritional

efficacy. BangladeshJ. Sci. Res. 11(1):17-20.Chowdhury, MAM and Rahman, MM. 1994. Autecological studies on the yield of BTl Tea (Camellia

sinensis L.) with special reference to drainage conditioDS. Bangladesh J. Life Sciences.6 (1):89-92.Chowdhury, MA.M and Rahman, MM.1991.Topographical effect on cultivation, nutriention and yield of

BTl Tea. BangladeshJ. 8ot..20(2):211-213.Chowdhury, MAMand Rahman, MM 1989. Ecological studies on the site potentialities, nutrients status

and Yield of tea (Camellia sinensis L.) m NPK and Caffeine in BTl twig tissues. Bangladesh J. Agric.Res. 14(3):269-271

Eden, T. 1976. Tea, Longman, Green and Co. LtdGazi,M.S. 1973. Distributional pattern of yield and vacancy of tea in Bangladesh..Tea Journal ofBangladesh.

Bangladesh Tea Research Institute. 14(2): 19-22.Jaeksoll, M.L. 1958. Soil ChemicalAnalysis, Prentice Hall Inc. Engle Wood Cliffs N.J. U.S.AJackson, M.L. 1973. Soil ChemicalAnalysis, Prentice Hall of India Private Limited, New Delhi.Misra, 1968. Ecology work book, Oxford and mH Publishing Company Calcutta, Bombay and New Delhi.MoUa, MM. 1981Study on the nature ofpoly-phenols in BTRI clones.Tea Journal ofBangladesh 17:20-25.Muttalib, A 2000.Personal Communication. Senior Scientific Officer,BTRISS,Odahlea, Chittagong.Rashid, Aand Choudll.ry,M.A1980. Rushing patterns and leaf composition of BTRI clones. Tea Journal of

Bangladesh. BTRI.l6(l&2) :13 -19.Stagg, G.V. and MiIIiD, D.J. 1975. The Nutritional and Therapeutic value of tea-A Review. J. Sci. Food Agric.

1439-145'4:26.TutOD, T.W. 1981. Growth and yield of tea bush. Experimental Agriculture. Dept of Civil Enginering

University of Southampton. U.K 17(3):323-332.Walkley, A and Black, C. A 1934. An examination of the Detjareffmethod for determining soil organic matter

and a proposed modification ofthe chromic acid titration method.Soi. Sci. 37:29-38.Wettestein, D. 1957, Formula ofchlorophyll determination. Expt. Cell Research. 3: 427-489.WiIIsoD, K.C. 1975b Studies on the Mineral Nutrition ofTea, IV. Potassium. Plant and Soil, 49: 279-293.WiIIIOIl, K. C. 1975a Studies on the Mineral Nutrition ofTea ll. Nitrogen, Plant and Soil, 42: So-S 16.

-45- Session' II