RATE OF ACCUMULATION OF DRY WEIGHT IN SEED OF SOYBEANS AND ITS RELATIONSHIP TO YIELD D. B. EGLI Department J Agrnmy, University f Kentucky, Leringtn, Ky. 40506. JurnalPaperN.T4-3-17. Received l7 Jan. 1971, accepted2i O.1971. Ect-t, D. B. 1975. Rate f accumulatin f dry weight in seed f sybeans and its relatinship t yield. Can. J. Plant Sci. 55: 215-219. The dry weight accumulatin rate in sybean (Glycine max (L.) Merrill) seed was measured fr 2 yr (197I-72), utilizing fbur cultivars and several planting dates within each year. Rates bserved ranged frm 3.38 t 8.32 mg/seed/day. There were significant differences amng cultivars and planting dates. There was n significant relatinship between the rate f accumulatin and grain yield, seed weight r final seed number. Grain yield was clsely crrelated with final seed number bth within each year and acrss bth years. On a mesur6 pur deux ann6es, 197 I et 1972,le taux d'accumulatin de la matilre sdche dans la graine de sja (Glycine mat (L.) Merrill) de quatre cultivars sem6s )r diff6rentes dates. Les taux bserv6s variaient de 3.38 d 8.32 mg/graine/jur. On a relev6 des diff6rences significatives entre les cultivars et entre les dates de semis, mais pas entre le taux d'accumulatin et le rcndement, le pids u le nmbre d6finitif de graines. Le rendement de graines a marqud une crr6latin 6trite avec le nmbre d6finitif de graines, et ce aussi bien h I'int6rieur de chaque ann6e que pur la myenne des deux ans. Yield prductin in grain crps may be crn (Zea mays L.) hybrids (Daynard et al. divided int three phases: (1) frmatin f 1971; Hanway and Russell 1969). Kller vegetativematerial, (2)frmatinf flwer (197 1) reprted that the grwth rate f rgans, and a "yield-cntainer," and (3) sybean seed was clsely related t the prductin, accumulatin and translcatin stage f develpment, and he suggested that f "yield-cntents" (Murata 1969). The the rate was cntrlled by regulatry yield accumulated in the third phase is a mechanisms within the seed. functin f the rate and the duratin f Duncan et al. (1965) studied the rate f grwth f individual crn kernels and fund accumulatin f dry weight in the seed. Several researchers have studied the av- that the daily rate f grwth was relatively erage rate f accumulatin f dry weight in insensitive t shrt-term fluctuatins in the the seed fractin f varius crp plants. envirnment. They cncluded that strage Hanway and Weber (191 l) reprted that carbhydrates served as a buffer between eight sybean (Glycine max (L.) Merrill) carbn fixatin and the accumulatin f dry cultivars, f varying yielding ability, had weight in the kernel. Data reprted by the same rate f accumulatin f dry weight Garner et al. (1914) fr sybeans can be in the seed. Egli and Leggett (1913) re- pltted t btain grwth rates f individual prted significant cultivar differences in seeds, and the rates btained fr three accumulatin rates with sybeans as well as cultivars ranged frm apprximately 5 t 15 a cultivar x year interactin. In bth cases, mg/seed/day. yield differences were related t variatins The fllwing experiments were cnin the duratin f the filling perid. Similar ducted t evaluate the relatinships between results have been reprted fr a number f the grwth rate f individual sybean seed Can. J. Plmt Sci. 55: 215-219 (Jan. 1975) and grain yield. 215
lt CANADIAN JOURNAL OF PLANT SCIENCE MATERIALS AND METHODS The experiments were cnducted fr 2 yr, l9'7 1-'72, at Lexingtn, Kentucky. The 1971 experiment cnsisted f fur cultivars (Amsy, Cutler,, and Yrk) planted at tw dates, 19 May and 7 July. Amsy is an early cultivar at Lexingtn; Cutler and are full seasn, and Yrk is late and frequently des nt mature befre the first frst. The cultivars were seeded in rws 76 cm wide, at a seeding rate f 30 seeds per meter f rw (394,744 plants/ha). Individual plts were six rws wide and 6 m lng. The experimental design was a split plt, with plant ing dates as main plts and cultivars as subplts in a randmized cmplete blck design with fur replicatins. The 1971 test was cnducted n a Dnerail silt lam sil, and 5 and 2.5 cm f water were applied with a sprinkler irrigatin system n 24 August and 2 September, respectively. ln 1972, three cultivars (Amsy, Cutler, and ) were planted at three dates: 5 May, 8 June, and 12 July. Owing t a lack f seed, was nt included in the third planting date. Plt arrangement and cultural practices were the same as the I97l test. The 1972 test was cnducted n a Maury silt lam sil, and 3.8, 2.8, and 7.0 cm f water were added with a sprinkler irrigatin system in July, August and September, respectively. The rate f dry weight increase in individual seeds was determined by the fllwing methd. Individual pds were tagged when they were apprximately 2-3 cm lng and befre there was a detectable seed weight. with the assumplin that since the pds were the same size they were apprximately the same age. Several hundred pds frm the center prtins f plants in each treatment were tagged. Nrmally, n mre than ne r tw pds per nde were tagged, and pds were tagged n nly ne interir rw f the six-rw plt. Pds were tagged n nly ne replicatin in 1971, and tw replicatins were used in 1972. X apprximately weekly intervals, l0 tagged pds were harvested frm each plt, separated int seed and pds, and dried t a cnstant weight at apprximately 70 C fr dry weight determinatin. Grain yield was measured n all fur replicatins by harvesting 5 m f single rw and threshing with a small plt thresher. Seed size was determined by weighing 100 randmly selected seeds frm each sample cllected- fr yield determinatrn. The dry weight accumulatin rate in individual seeds was estimated by fitting a linear regressin line t the seed weights after excluding the bviusly nn-linear pints frm the beginning and the end fthe filling perid. Least square techniques were used t fit the curves. Fr the 197 data, a t test was used t test fr hmgeneity f the regressin cefficients fr a given cultivar acrss the tw planting dates (Steel and Trrie 1960). In 19'72, rates were calculated fr each individual plt and an analysis f variance was cnducted n the rates. Seed number was calculated by dividing the final grain yield by the average seed size. RESULTS AND DISCUSSIONS The grwth curves btained frm Cutler in 1912 Ne shwn in Fig. l Curves btained fr the ther cultivars and ther planting dates were similar. In general, the lag phase assciated with grwth f the individual seeds was relatively shrt, and the seeds rapidly entered the linear phase f grwth. The Iinear phase extended until nearly maximum size was reached and grwth terminated. The accumulatin f dry weight in the pds usually had reached a maximum by the time the seeds had accumulated 15-30% f F = ; = E u a U E Cutler- 1972 01020304050 DAYS AFTER FIRST SAMPLE Fig. 1. The accumulatin f dry weight in seed and pds f Cutler sybeans.
EGLI-DRY WEIGHT ACCUMULATION IN SOYBEANS 2l'7 their final weight. There was n cnsistent indicatin f a decline in pd weight as the seed reached their maximum dry weight. The dry weight accumulatin rates in the seed fr the varius treatment cmbinatins are shwn in Table l. The r2 values fr the regressin lines were all greater than 0.90 and the majrity were greater than 0.96. The number f samples utilized fr estimating the rates varied frm five t nine. Since the tagged pds were cllected frm the center prtin f the plant where the majrity f the pds were lcated, the rates btained were assumed t be representative f the majrity f the seeds n the plant. The rates bserved ranged frm 3.38 t 8.32 mg/seed/day. In 1972, Cutler was significantly higher than Amsy and fr the first tw planting dates; hwever, the rate fr Amsy was larger than Cutler at the third planting date. The rate f Amsy increased as planting was delayed, with the rate at the third planting date being mre than duble the rate at the first date. The rate fr als increased as planting was delayed. Cutler exhibited the highest rate at the secnd date, and the rate at the first planting date was nt significantly different frm the third planting date. Table 1. The rate f accumulatin f dry weight in individual sybean seed (mg/seed/day) Cultivar Amsy Cutler Yrk Mean Amsy Cutler Mean 6.27 5. l6 4.99 5.79 5.56 Planting date 1971 6.18 6.22 5.92 5.54 4.63 4.81 5.61 s.73 s.60 1 972 3.96 5.25 8.32 5.84 5. 13 6.63 5.28 5.68 3.38 5.36 - +.J I 4.16 5.15 6.80 1972: LSD (0.05) : 0.81 mg/seed/day LSD (0.01) : 1.20 mg/seediday In 197 l, there was n significant difference between planting dates with a cultivar. It was nt pssible t test fr differences between cultivars in 1971;' hwever, cnsidering the variatin in the 1912 experiment, there were prbably real differences between cultivars in 197 I als. The rate f grwth f individual seeds reprted in this paper is similar t sme f thse reprted by Garner et al. (1914), althugh it is interesting t nte that ne cultivar that they used had a rate apprximately twice as large as any btained in these experiments. Cmparisn f the cultivar means fr l91l and 1972 suggests that the rate f accumulatin f dry weight in the seed may be a characteristic f a particular cultivar. Averaged acrss all dates f planting, Amsy had the highest rate in bth years, fllwed by Cutler, and had the lwest rate. Hwever, there was variatin assciated with planting dates and years, indicating that envirnmental factrs had a cnsiderable influence either directly r indirectly n the rate f grwth. In 191 l, the average grain yield f all cultivars was reduced by 360/ when planting was delayed until 7 July (Table 2). Yield reductins in 19'72 were l8vc, fr the secnd planting date and 29% fr the third planting date. The reductin in grain yield was primarily a result f reductins in seed number and nt a result f decreases in seed weight (Table 2). Seed number, averaged acrss cultivars, was reduced 33Vc in 1971 when planting was delayed until 7 July, with reductins f 17 and 32V fr the secnd and third planting, respectively, in 1972. Yield was clsely crrelated with seed number within each year (r:0.88 in l9'7l; r:0.82 in 1912) and acrss bth years (r:0.89). The cnelatin cefficients f the dry weight accumulatin rate in the seed with grain yield, number f seeds per hectare and average seed weight were -0.388, -0.309, and -0.089, respectively, and they were all nnsignificant. Thus, the rate f accumulatin f weight in the seed did
218 canadian JuRNAL -b plant' sctence Table 2. Yield, seed weight, and seed number f sybeans as influcnced by cultivar and planting date Yield (kg/ha) Seed weight (mg/seed) Seeds/ha x l0- Planting date Planting date Planting date 3 Mean Amsy 2,912 Cutler 2.8 1 8 Yrk 2320 2,8-58 Mean 2,121 LSD (0.0s) : 524kglha LSD (0.01):894kg/ha Amsy 3,800 2.898 Cutler 3,134 2,321 3,451 3,268 Mean 3,164 2,831 LSD (0.0s) : 603 kg/ha LSD (0.01) :820 kg/ha 715 ) t)4,728 2,273 r,688 2,004 t,829 2,341 1,145 2,629 3,t09 2,280 2,580-3,362 2.454 nt appear t be related t grain yield, final sink size, i.e., the number f seeds per unit area, r t average seed weight. The accumulatin f weight in the seed shuld be related t the ability f the plant cmmunity t fix carbn during the filling perid r the translcatin f strage carbhydrates frm ther plant parts. The lack f a relatinship between yield and rate suggests that envirnmental influences acting during the filling perid as expressed by the rate f accumulatin were relatively unimprtant in determining yield in this experiment. Yshiada (19'72) suggested that grain yields can be limited by either yield capacity (seed number and ptential seed size) r by the ability t realize that capacity. The ability f a crp plant t realize its capacity is a functin f the rate and the duratin f accumulatin f dry weight in the seed fractin. The data presented here suggest that the rate f accumulatin f dry weight in the seed during the linear grwth phase was nt an imprtant yield-determining factr. 1971 155-176 r90-194 t49-146 183-143 169-165 21 mg/seed 32 mg/seed 1 972 114 tll 165 t52 157 148 l3l 128 152 154 156 t66 192 148 163 172 r52 r30 r </ 18.8 14.8 15.6 15.6 t.l 21.8 16.4 20.6 14.8 26.4 25.5 22.9 18.9 9.8 r4.3 8.9 11.8 l 1.6 13.6 12.8 14.2 10.8 r5.9 I 5.4 t5.6 18.0 16.9 26.O Yield capacity is a functin f seed number and ptential seed size. Yields btained in this experiment were clsely related t seed number. Seed nurnber, as calculated in this paper, was influenced bth by pd set and by the number f seed per pd. Shaw and Laing (1966) reprted that misture stress early in the pd filling stage culd cause reductins in the number f seeds per pd as well as in the number f pds per plant. Thus, the final seed number, as calculated here, was influenced by flwer and pd abrtin as well as by pssible reductins in seeds per pd, and may be lwer than the seed number at the end f flwering. The seed size aspect f yield capacity is smewhat mre difficult t evaluate as a yield-limiting factr. Hwever, the seed weights btained in these experiments were nly 60 t 80Va f the largest seed weights btained fr these cultivars in tests at a number f lcatins and years. This indirect evidence suggests that the seed size aspect f yield capacity was nt a limiting factr. The grain yield f sybeans in this study
EGLI-DRY WEIGHT ACCULUMATION IN SOYBEANS 2t9 was nt related t the rate f accumulatin f dry weight in the individual seed, althugh there were differences in rates amng cultivars and envirnments. Differences in grain yields were clsely related t variatins in final seed number, althugh it was nt clear whether yield capacity was limiting final yield. Whether yield capacity r the ability t realize that capacity is mst cmmnly limiting sybean yields is an area that needs further research. DAYNARD, T. B., TANNER, J. W, ANd DUNCAN, W. G. 1971. Duratin f the grain filling perid and its relatin t grain yield in crn,zeamaysl. Crp Sci. 11: 45-48. DUNCAN, W, G., HATFIELD, A. L. ANd RAGLAND, J. L. 1965. The grwth and yield f crn. II. Daily grwth f crn kernels. Agrn. J.57 221-223. EGLI, D. B. and LEGGETT, J. E. 1973. Dry matter accumulatin patterns in determinate and indeterminate sybeans. Crp Sci. 13 : 220-222. GARNER, W. W., ALLARD, H. A. ANd FOUBERT, C. L. 1914. Oil cntent f seeds as affected by the nutritin f the plant. J. Agric. Res.3:22'7-249. HANWAY. J. J. and RUSSELL, W. A. 1969. Dry matter accumulatin in crn (Zea ma1's L ) plants: Cmparisn amng single-crss hybrids. Agrn J. 6l:941-951. HANWAY, J. J. and WEBER, C. R. 1971. Dry matter accumulatin in eight sybean (Glycine max (L.') Merrill) varieties. Agrn. J. 63: 22',7-230. KOLLER, H. R. 1971. Analysis f grwth within distinct strata f thc sybean cmmunity. Crp Sci. 11:400-402. MURATA, Y. 1969. Physilgical respnses t nitrgen in plants. Pages 235-259 in J D. Eastin, ed. Physilgical aspects f crp yield. American Sciety f Agrnmy, Madisn, Wiscnsin. SHAW. R. H. and LAING, D. R. 1966. Misture stress and plant respnse. Page s 73-94 inw. H. Pierre. ed. Plant envirnment and efficient water use. American Sciety f Agrnmy, Madisn. Wis. STEEL. R. G. D. and TORRIE, J. H. 1960. Principles and prcedures f statistics. McGraw-Hill Bk C., New Yrk, N.Y p. t73. YOSHIADA. S. 1972. Physilgical aspects f grain yield. Amer. Rev. Plant Physil.23: 437-464.