J. Agronomy &: Crop Science 163, 105—108 (1989)© 1989 Paui Parey Scientific Publishers, Berlin and HamburgISSN 0931-2250

Faculty of Agriculture, University of Peradeniya, Sri Lanka

Relationship between Seed Characters, Plant Growthand Yield Parameters of Phaseolus vulgaris

U. R. SANGAKKARA

Author's address: Dr. U. R. SANCAKKARA, Faculty of Agriculture, University of Peradeniya, Sri Lanka.

mtb 3 tables

Received October 15, 1988; accepted fanuary 23, 1989

Abstract

Legumes are an important component of the dietary pattern of the developing world. Thus optimal yields area vital factor in agricultural production in these countries. Seed characters affect plant growth and yields ofgrain legumes. Due to the lack of similar studies in Phaseolus vulgaris (Frenchbeans), a study was carried outto determine the effect of seed characters on the growth cycle of frenchbean plants. Seed size was primarilydetermined by the size and weight of cotyledons and seed coat, as embryo size was similar in all seed classes.Seed size had no effect on seed viability, although larger seeds germinated earlier. There was a positiverelationship between seed size and plant growth characters. Larger seeds developed plants with better growthand yield component parameters, resulting in higher yields. The importance of determining seed size infrenchbeans is presented.

Introduction

Legumes are an important nutritious food re-source for humans and animals, as the pro-ducts contain a high content of proteins and insome instances, oil (NAS 1984). In addition,their relatively short growth period and adap-tability makes them ideal components of thefarming systems of the developing world.Thus, large extents of the agricultural lands ofthe developing world are cultivated with manylegumes, among which Phaseolus vulgaris L.(Frenchbean) is considered the most promi-nent vegetable species (TINDALL 1984).

Several species characters affect the successof an established legume crop. Amongst these,seed size has been recognized as a factor deter-mining seedling vigour, plant growth andyield. Thus, several reports (e.g. BLACK 1957,EL SAEED 1967, SMITH and CAMPER 1975) illus-

trate positive relationships between seedcharacters and vegetative and/or reproductivegrowth of legumes.

The primary seed character associated withsuperior plant growth is seed vigour (HEVDECK-

ER 1972). Seed vigour thus has been defined as'Effects on seed crop performance which isattributed to seed characters' (PINTHUS andKiMEL 1979). Thus, physical characteristics ofseeds and speed of germination are consideredkey factors in determining seed vigour.

While many reports illustrate relationshipsbetween seed size and subsequent plant growthof grain legumes, similar research is not widelyreported on frenchbeans, which is an impor-tant vegetable species. However, the potentialfor increasing yield requires studies in relationto seed characters of this species, especially dueto the relative ease of grading the large seeds.Thus, a study was carried out to determine the

U.S. Copyright Clearance Center Code Statement: 093 1-2250/89/6302-01 05$02.50/0

106 SANGAKKARA

seed characters of frenchbeans and their effectson emergence, plant growth and yields over awet and dry season.

Materials and Methods

The study was carried out over a wet and dry seasonof a given year, at the University Experimental Sta-tion, Kundasale, Sri Lanka (7°N, 81^E, 420 MetersASL), using a randomized block design with fourreplicates in each season.

Seeds of frenchbean (Variety Topcrop) was ob-tained from a commercial source, and graded intofour seed categories based on appearance and indi-vidual seed weight. The four categories obtainedwere — seeds weighing OA—0.49 g; 0.3—0.39 g;0.2—0.29 g and 0.1—0.19 g. Subsamples of theseseeds were dissected and dy weights of seed compo-nents determined by drying at 80 °C for 48 hours.

The four seed classes were planted with the onsetof the two seasons onto a well prepared seed bed on amoist Alfisol (pH 6.43; Total N % 0.21; Available P39.42 ppm; CEC 1141 MMoles/kg soil), with fiverows of each seed category containing 30 plants perplot per replicate. The fertilizer added was 90 kg • N,135 kg • P:O5 and 100 kg • K.O per ha, as recom-mended for frenchbeans (TiNDALL 1983). The soilwas kept weed free and water added at regularintervals to maintain adequate soil moisture.

The following data was gathered in both seasons:Days to 75 % emergence, plant dry weights upto

pod set by periodic harvests of three plants per seedclass and drying at 80 °C for 48 hours, days to 50 %flowering, flowers per plant, percentage pod set andyields of pods per plant. In addition, 100 seed weightwas determined after obtaining the yields of freshpods per plant.

Plant growth over the season upto pod set wasdetermined by calculating the growth rate using theequation Log^ Y + A -I- BX, where Y and X are dryweights (g) and time (days) respectively. The datawas pooled for analysis in situations where therewere no significant differences between seasons.

Results and Discussion

The dry weights of components of seeds of thefour weight classes and the cotyledon : embryoratios are presented in Table 1. Larger seedshad heavier seed coats and cotyledons. In con-trast, the weights embryos in all seed classeswere similar. Thus, the data indicates that seedsize of frenchbeans is determined by the seedcoat and cotyledons and the embryos of allseeds are similar. Comparison of ratios whichindicate the resources available for embryogrowth and development during early stages ofgermination show that larger seeds have a grea-ter food reserve due to larger cotyledons. Smallseeds have a lower food reserve for embryogrowth, which can be considered a setbackduring germination and plant establishment.

Seed size has a significant effect on emer-gence of frenchbeans (Table 2). Large seedsgerminate earlier and the time taken by smallerseeds to reach 75 % emergence was approxi-mately 57 % greater than time taken by largerseeds. This can be attributed to the availabilityof a larger resource of food for the growingembryo in larger seeds which promotes seed-ling development. The above trend does notvary with the season. Thus seasonal effects donot determine the rate of emergence due to theprovision of a favourable environment atplanting. There were no differences in thenumbers of emerged seedlings between thedifferent seed classes, suggesting the similarityof seed viability in these different sized seeds.Thus, seed size has no effect on the capacit)'for germination in frenchbean seeds.

The effect of seed size on plant growth andyield parameters are presented in Table 3. Thetrend of results in the two seasons are similar.Larger seeds give rise to significantly betterplant growth than smaller seeds.

Table 1. Characteristics of bean seeds of different sizes

Seed size Seed coatdry wt. (mg)

36.933.921.724.8

3.22

Cotyledonsdry wt. (mg)

394.2322.6211.4143.823.65

Embryodry wt. (mg)

3.22.82.92.70.21

Cotelydon :embryo ratio

123.18115.1772.8952.9612.98

• —

0.4—0.49 g0.3—0.39 g0.2—0.29 g0.1—0.19 gLSD (P - 0.05)

Relationship between Seed Characters, Plant Growth and Yield Parameters 107

Table 2. Effect of seed size on 75 % emergence ofbean seeds

Seed size Days to 75 % emergence

0.4—0.49 g0.3—0.39 g0.2—0.29 g0.1—0.19 gLSD (P = 0.05)

6.56.88.7

10.21.46

This IS due to earlier emergence of largerseeds (Table 2) which grows from a similarsized embryo but is nourished by a largerendosperm. The data conforms to reports onother grain legumes (SMITH and CAMPER 1975),and a positive relationship can be developedbetween seed size and plant growth of thisspecies. In addition, the larger seedlings tendto produce a more extensive root and shootsystem which has a greater ability to obtaingrowth resources from the environment moreefficiently (HARPER 1977), thereby maintainingthe superior growth form throughout the lifecycle.

Yield parameters (Table 3) follow that ofseed characters. Plants from larger seeds flowerearlier primarily due to the inherent vigour ofthese plants. Due to more rapid growth, theseplants mature earlier and produced a greaternumber of flowers per plant than plants fromsmall seeds. The smaller plants due to slower

growth reaches maturity later and are not cap-able of producing a larger number of flowers.Thus, the differences in days to 50 % flower-ing and the number of flowers per plant be-tween plants from larger and smaller seed clas-ses are 45 % and 37 % respectively.

Plants produced from small seeds show alower percentage of pod set. This is attributedto the greater loss of flowers and developingpods in these plants due to the inability of theplant to support a larger number of reproduc-tive points. In contrast, plants from largerseeds retain a greater proportion of the initi-ated flowers due to inherent plant vigour.

The yields per plant follow the pattern ofseed size. This also conforms to results of grainlegumes (SMITH and CAMPER 1975, PINTHUS andKiMEL 1979). This phenomenon can be relatedto the greater yield components of plants aris-ing from larger seeds and more efficient physi-ological and biochemical activity of vigorousseedlings (CHING 1973) which results in greateryields.

The 100 seed weights conform to initial seedsize. Plants from larger seeds produce biggerand heavier seeds. This again could be associ-ated with high plant vigour and greaterbiochemical activity within the plant leading tomore efficient translocation of photosynthatesto the growing sinks of seeds. Plants fromsmaller seeds seem to be less efficient in meet-ing the demands of the sinks caused by grow-ing seeds.

Table 3. Effect of seed characters on growth and yield parameters of beans in wet and dry seasons

Seed size

Wet season

0.4—0.49 g0.3—0.39 g0.2—0.29 g0.1-0.19 gLSD (P = 0.05)

Dry season

0.4—0.49 g0.3—0.39 g0.2—0.29 g0.1-0.19 gLSD (P = 0.05)

Plantgrowth*"

0.2340.2160.1960.1670.003

0.1980.1750.1330.1120.006

Days toflower

22.824.129.333.22.02

24.329.733.536.7

1.29

Flowers/plant

28.724.420.817.81.24

23.718.515.109.72.62

% Pod set

74.481.676.962.86.77

69.460.875.447.55.7

100 seed wt

(g)

34.7532.8527.3522.22

2.32

30.8528.5522.1817.253.79

Yield/plant

(g)

94.396.17S.669.65.83

80.771.752.744.8

7.25

108 SANGAKKARA, Relationship between Seed Characters, Plant Crowth and Yield Parameters

Although the trend in plant growth is simi-lar, comparison of performances of plantsfrom different seed sizes in the two seasonsshow better growth and yields during the wetseason. This is primarily due to the more fa-vourable environment present during the wetseason for growth of frenchbeans. Hence, dif-ferences between yield components and yieldsin plants growing from large and small seedclasses is greater in the dry season. For exam-ple, reduction in the number of flowers inplants from large and small seeds in the wetseason is 16 % in contrast to 31 % in the dryseason. Similarly, yield differences betweenplants of the two categories in the wet and dryseason were 26 % and 43 % respectively.Thus, the data illustrate the greater effect ofseed size on subsequent plant performancedurmg unfavourable seasons.

The results of the study illustrates the use-fulness of seed characters on indices of subse-quent plant performance. Thus, selection oflarge uniform seeds are important in the pro-duction of frenchbeans. This ensures a moreuniform crop with greater vigour which arecapable of producing a higher yield. Use ofnonuniform or small seeds is detrimental interms of poor plant performance and yieldsresulting in lower economic returns. The selec-tion of seeds become more important duringdry seasons or in environments marginallysuited for frenchbeans as the effects of seed sizeare more prominent under unfavourable con-ditions.

Zusammenfassung

Beziehungen zwischen Sameneigenschaften,Parametern des Pflanzenwachstums und -er-trages von Phaseolus vulgaris

Leguminosen sind eine bedeutende Kompo-nente der Nahrungsversorgung in Entwick-lungslandern. Hohe Ertrage sind daher ein vi-taler Faktor in der landwirtschaftlichen Pro-duktion in diesen Landern. Sameneigenschaf-ten beeinflussen das Pflanzen wachstum unddie Ertrage von Kornerleguminosen. Es wurde

daher eine Untersuchung durchgefuhrt, umden Einfluf̂ der Sameneigenschaften auf denWachstumsverlauf von Buschbohnenpflanzenzu untersuchen. Die Samengrof^e war in ersterLinie durch die Grofte und das Gewicht derKotyledonen und der Samenschale bestimmt,wahrend die Grofie des Embryos in alien Sa-menklassen gleich war. Die Samengrof̂ e hattekeinen Einflul̂ auf die Samenwuchskraft; gro-f5ere Samen keimten allerdings rascher. Es gabeine positive Beziehung zwischen der Samen-groEe und den Wachstumseigenschaften. Gro-£ere Samen entwickelten Pflanzen mit besse-rem Wachstum und Ertragsstrukturkompo-nenten, was zu einem hoheren Ertrag fuhrte.Die Bedeutung der SamengroEe fiir Buschboh-nen wird besprochen.

Acknowledgements

Gratitude is expressed to Mr. T. S. GUNASEKERA forresearch assistance and Mrs. S. MEEGAHAKUMBURA

for secretarial assistance.

References

BLACK, J. N., 1957: The early vegetative growth ofthree strains of subterranian clover in relation tosize of seed. Australian Journal of AgriculturalResearch 8, 1—14.

CHING, T . M. , 1973: Biochemical aspects of seedvigour. Seed Science and Technology 1, 73—88.

EL SAEED, E. A. K., 1967: Seed size as a varietaldifference in broadbeans {Viaa faba). Journal ofAgricultural Science 68, 69—73.

HARPER, J. L., 1977: Population Biology of plants.Academic Press, U.K. 892 pp.

HEYDEGKER, W. , 1972: Vigour. In: ROBERTS, E. H.(ed.), Viability of seeds. Chapman & Hall, U.K.,209—252.

NAS, 1984: Tropical legumes — resources for thefuture. National Academy of Science, Washington,USA. 332 pp.

PiNTHUS, M. J., and U. KiMEL, 1979: Speed ofgermination as a criterion of seed vigour m soy-beans. Crop Science 19, 291—292.

SMITH, T . J., and A. M. CAMPER, 1975: Effect ofseed size on soybean performance. AgronomyJournal 67, 681—684.

TiNDALL, H. S., 1983: Vegetables in the tropics.Mcmillan, London, U.K. 533 pp.