Seed-filling Period Research Articles

Phenotypic variation of Vicia pannonica Crantz (var. pannonica and var purpurascens ) in central Turkey

Hungarian vetch (Vicia pannonica Crantz.) is an important forage crop in both central Turkey (CT) and central European countries. It can be grown in CT as winter crop, but frequent spring droughts cause yield losses. Our objectives were (I) to investigate agro-biological variation among populations, (II) to identify useful plant characters and (III) to develop selection strategies. Forty-five accessions of both var. pannonica and var. purpurascens were evaluated for the 11 plant characters in 2002/03 cropping season. Var. pannonica was late flowering, had more stems and seeds per pod, and longer stems and pods. Var. purpurascens had earlier flowering, more days to physiological maturity, more pods, greater plant biomass and heavier seeds. As var. purpurascens was early flowering, its longer seed-filling period is likely to contribute to greater seed size and weight. However, in var. pannonica, late flowering and ensuing delayed maturity caused strong negative associations between days-toharvest and other characters. If the earliness, higher biomass and seed size from var. purpurascens, and the many long stems and long pods from var. pannonica could be incorporated into one or more genotypes through Mendelian crossings, seed and hay yields would be substantially increased.

Photoperiodic effect on flowering and seed development in quinoa (Chenopodium quinoa Willd.)

Sensitivity to photoperiod in quinoa (Chenopodium quinoa Willd.) was studied under controlled conditions to enhance crop adaptation to environments outside its centre of origin. Two varieties, a traditional variety from Bolivia (Real), which will not mature under Danish conditions, and an early maturing variety (Q52), developed for Danish climatic conditions, were used in this reciprocal transfer experiment. Plants were moved from a short daylength of 10 h (SD) to a long daylength of 18 h (LD) and vice versa at set intervals from sowing to 100 days after sowing (DAS). A reaction of LD in time to flowering was observed only in the Bolivian variety Real. Under SD both varieties flowered after 39 DAS. For Real the LD regime resulted in a moderate increase in time to flowering to 44 DAS. The non-sensitive, juvenile period in Real was estimated to be approximately 16 days. In Q52 a moderate increase in the number of leaves was formed on the main stem after flowering at LD, which indicates that some daylength sensitivity remains. The most striking difference occurred during seed filling, when going from SD to LD. In Q52 the time from the end of flowering to maturity increased from 39 to 52 days. Under SD, Real had a seed-filling period similar to Q52, but at LD Real remained with green leaves during seed filling. Hard seed was observed in the still green perigonium 57 days after end of flowering. At this moment re-shooting occurred from the inflorescence, and seed maturity was not reached at the termination of the experiment at 150 DAS. This study shows that flower induction is not a major problem for adaptation of quinoa to North European conditions but that a very strong, daylength sensitive, stay green reaction is the main cause of the late maturity of South American introductions.

Relationships between seed yield and yield components in common vetch ( Vicia sativa ssp. sativa) populations sown in spring and autumn in central Turkey

In order to investigate the effect of two growing seasons on seed yield, to provide a hypothetical basis to demonstrate the relations of the main agronomic characters and their influences with vetch seed yield, 20 genotypes were grown at two sowing dates, replicated over two seasons at the Research Farm of the Central Research Institute for Field Crops near Ankara in 2001–2004. Fifteen plant characters were measured: seed yield, days to flowering, days to harvest, days to physiological maturity, stem length, number of stems, number of pods, pod length, number of seed per pod, 1000-seed weight, harvest index, biomass, biomass growth rate, seed growth rate and winter death. Results were analysed by multiple statistical analysis: analysis of variance, simple correlation, factor analysis, principle component analysis, path analysis and cluster analyses. Vetch growth and development were strongly affected by sowing in spring or autumn. Though seed-filling period and 1000-seed weight were significantly higher in autumn vetch than in spring vetch, spring vetch produced higher biomass and seed yield. Winter damage severely reduced yield in autumn vetch, and in the absence of winter hardy varieties spring planting must be preferred. The dependence of seed yield on days to harvest, biomass, and biomass and seed growth rates were common to both planting seasons. In spring-sown crops, seed yield also depended on days to physiological maturity, and in autumn-sown crops seed yield depended on harvest index. Faster seed filling had a stronger effect on seed yield than did early flowering. Therefore, early maturity, combined with rapid dry matter accumulation, was expressed as a high biomass, which laid the potential for a greater seed yield. In conclusion, the traits of most interest when selecting common vetch plants to improve seed yield under cold and drought stress conditions are early harvest with faster seed filling and high biomass with higher biomass growth rate.

Growth and nitrogen dynamics of spring chickpea genotypes in a Mediterranean-type climate

SUMMARYChickpea (Cicer arietinum L.) is an important legume of rainfed farming systems, contributing to the sustainability of production and reducing the need for nitrogen (N) fertilization through fixing atmospheric N2. The relative importance of factors causing variations in growth, seed yield, N accumulation and N utilization efficiency among spring chickpea varieties grown in a Mediterranean-type climate was investigated in field experiments conducted in 2003 and 2004. Five chickpea varieties were grown in a silty clay soil in the farm of the Democritus University of Thrace in Orestiada, Greece. Yearly differences in plant growth and productivity were observed and were mainly associated with the variations in the weather parameters between the growing seasons. Nitrogen utilization efficiency (NUE) for biomass production during the seed-filling period was higher compared with that during the vegetative period. NUE for seed yield (SY) ranged from 18·3 to 24·5 g dry matter (DM)/g N and was positively correlated with seed yield, suggesting that high SY was associated with more efficient exploitation of N. When the environmental conditions favoured high early N accumulation, the differences among varieties in NUE were mainly due to the differences in N partitioning at maturity, e.g. the nitrogen harvest index (NHI). The amount and the efficiency of N content at the beginning of seed growth (growth stage (GS) R5) that was translocated to the seed differed among varieties and ranged from 7·0 to 16·6 g N/m2 and from 68·2 to 86·8 g DM/g N, respectively. Most of the variation (0·96) between varieties in N translocation could be accounted for by the differences in total N content at GS R5. N losses from the plant foliage between 0·61 and 9·92 g N/m2 were detected during the seed-filling period when SY was low and N content at GS R5 was high.

Water Deficit Effect on the Relationship between Temperature during the Seed Fill Period and Soybean Seed Oil and Protein Concentrations

Since most soybean [Glycine max (L.) Merr.] seed is processed into meal and oil, there is a growing concern about environmental effects on soybean seed composition. The aim of this work was to investigate how water deficit affects the well‐known relationship of soybean seed oil and protein concentrations with temperature and, alternatively, with solar radiation during seed fill. We analyzed oil and protein data from multienvironment trials in Argentina (latitude 29° to 38° S). Multiple linear regressions were used to test the effect of water deficit on the relationship between oil, protein, and oil + protein and temperature. The functions relating oil and protein concentrations with average daily mean temperature during seed fill (TmR5R7) changed with water deficit. When precipitation minus potential evapotranspiration during the reproductive period (pp‐PETR1R7) was lower than 70 mm, oil increased linearly with increasing TmR5R7 and with rising water deficit. Meanwhile, protein increased linearly with TmR5R7 but decreased linearly with water deficit. Oil + protein concentration held a linear relationship with TmR5R7 even under water deficit. Cumulative solar radiation during seed fill predicts seed quality but shows lower significance than TmR5R7 This research demonstrates that a water‐stress indicator (pp‐PETR1R7) should be considered in rainfed crops because it affects the well‐known relationship of soybean seed oil and protein concentrations with temperature.

A comparison of NDVI and MTVI2 for estimating LAI using CHRIS imagery: a case study in wheat

Leaf area index (LAI) is a key variable in crop growth models. The derivation of reliable LAI maps from satellite imagery would provide a means of spatially extrapolating these models. During the 2004 and 2005 growing seasons, hyperspectral data from the Compact High Resolution Imaging Spectrometer (CHRIS) sensor were acquired over a wheat crop in southern Alberta. The ability to obtain reliable LAI estimates from CHRIS data was investigated using a preexisting relationship between LAI and the modified transformed vegetation index (MTVI2). The performance of the recently develop MTVI2 in estimating LAI was compared to that of the more commonly used normalized difference vegetation index (NDVI). Both narrow and broad bands simulated from the CHRIS data were used in calculating the NDVI. All vegetation indices provided good relationships with LAI (R2 = 0.70–0.90). The errors in the estimated LAI values varied with vegetation index and were dependent on growth stage. The MTVI2 performed better than the NDVI at full canopy closure. Confirming previous reports in the literature, the NDVI tended to saturate at LAI values of 37–4, which resulted in an underestimation of LAI at full canopy closure. There was no benefit to using narrow spectral bands in the NDVI. Estimation of LAI using the MTVI2 was underestimated late in the season during the seed-filling period.

Soybean Genetic Improvement in Yield and the Effect of Late‐Season Shading and Nitrogen Source and Supply

Genetic improvement in soybean [Glycine max (L.) Merr.] yield has been associated with both assimilate and N accumulation [especially from dinitrogen (N2) fixation] during the seed‐filling period (SFP). Therefore, the physiological factors associated with genetic improvement may be dependent on abundant assimilate and N supply. The objectives of this study were to quantify genetic improvement in yield under: (i) assimilate limiting conditions, (ii) under low N fertility, and (iii) when either inorganic N fertilizer or N2 fixation is the main source of N. A randomized complete block experiment was conducted at two locations in 1998 and one in 1999. The main plot factor included no shade or a 63% shade treatment imposed after the R4/R5 developmental stage. The split plot factors were three N treatments: (i) inoculated, (ii) uninoculated with no additional fertilizer, and (iii) uninoculated plus fertilizer N. The split‐split plots were four cultivars, representing a pair of older and a pair of newer cultivars. Shading reduced dry matter (DM) accumulation, and both shading and N limitation reduced N accumulation and seed yield. However, the newer cultivars consistently maintained their yield advantage over the older cultivars under both shading and N limiting conditions as well as when the source of N was soil available N or N2 fixation. The results of the study suggest that the physiological factors that contribute to genetic improvement in yield are not dependent on the level of incident radiation during the SFP, or the source or availability of N during the SFP.

Nitrogen utilization efficiency of safflower hybrids and open-pollinated varieties under Mediterranean conditions

The identification of the factors determining nutrient utilization of safflower ( Carthamus tinctorius L.) is useful for the successful introduction of the crop to the cropping system of a region. A field study was conducted to compare and analyze the relative importance of the various component traits causing variation in nitrogen utilization efficiency (NUE) of safflower under Mediterranean conditions. Ten genotypes, four hybrids and six open-pollinated varieties, were grown for two growing seasons without irrigation, on a silty clay (Typic Xerorthent) soil. Seed yield varied greatly among genotypes and ranged from 923 to 3391 kg ha −1. Hybrids showed a mean seed yield superiority of 12.5% against varieties. Seed yield was the most important component of seed N yield and its contribution to the total variation in seed N yield among genotypes was at least 53%. NUE for biomass production during the seed-filling period was lower compared to that during the vegetative period. Genotypes differed in NUE for seed production (NUE s) and the differences followed those of nitrogen harvest index (NHI). The contribution of NHI to the total variation in NUE s among genotypes was much greater compared to that of yield per unit seed nitrogen and accounted for more than 79%. NUE s is positively correlated with seed yield, suggesting that high yield was probably associated with more efficient exploitation of nitrogen. NUE s is negatively correlated with (leaf + stem) N concentration at maturity, meaning that low straw N concentration may be indication of higher NUE s. Results indicated that selection for NUE in safflower should be based on multiple criteria rather than just one criterion and also should be accompanied by evaluation for seed yield to ensure an improvement in both traits.

High Carbon Requirements for Seed Production in Soybeans [Glycine max (L.) Merr.

In soybeans, increase in the dry weight of seed (IWS) during the seed-filling period (SFP) is nearly half that of the whole plant (IWP). Hence, the contributions of assimilate during SFP to seed growth in soybeans is apparently lower than that in other cereal crops. However, analysis of the assimilate budget for seed production based on dry matter could be misleading in soybeans because the carbon (C) contents of seed and that of other organs are different due to the differences in lipid and protein content and respiration loss in each organ results in underestimation of the C contribution to seed production. In field soybeans, irrespective of shading and thinning, IWS/IWP and harvest index (HIW) for dry weight were slightly lower than ICS/ICP and HIC for C, respectively. Of the 13C fed at the vegetative stage and early SFP, 3.4% and 16.4%, respectively were accumulated in the seed, 0.9% and 28.2%, respectively, in the pod shell and 26.8% and 37.8%, respectively were respired before maturity. Ninety-six percent of seed C was assimilated during the SFP. Respiratory loss of 13C fed at the early SFP was larger than that from 13C at the vegetative stage, showing that seed production requires much more C than leaf or stem growth. These results suggest that the difference in C contents between plant organs has little effect on the estimation of assimilate partition into soybean seeds based on dry matter, and high respiration loss for seed growth reduces the partition of dry matter into seeds.

Soybean Genetic Improvement in Yield and the Effect of Late-Season Shading and Nitrogen Source and Supply

Genetic improvement in soybean [Glycine max (L.) Merr.] yield has been associated with both assimilate and N accumulation [especially from dinitrogen (N2) fixation] during the seed-filling period (SFP). Therefore, the physiological factors associated with genetic improvement may be dependent on abundant assimilate and N supply. The objectives of this study were to quantify genetic improvement in yield under: (i) assimilate limiting conditions, (ii) under low N fertility, and (iii) when either inorganic N fertilizer or N2 fixation is the main source of N. A randomized complete block experiment was conducted at two locations in 1998 and one in 1999. The main plot factor included no shade or a 63% shade treatment imposed after the R4/R5 developmental stage. The split plot factors were three N treatments: (i) inoculated, (ii) uninoculated with no additional fertilizer, and (iii) uninoculated plus fertilizer N. The split-split plots were four cultivars, representing a pair of older and a pair of newer cultivars. Shading reduced dry matter (DM) accumulation, and both shading and N limitation reduced N accumulation and seed yield. However, the newer cultivars consistently maintained their yield advantage over the older cultivars under both shading and N limiting conditions as well as when the source of N was soil available N or N2 fixation. The results of the study suggest that the physiological factors that contribute to genetic improvement in yield are not dependent on the level of incident radiation during the SFP, or the source or availability of N during the SFP.

The Relationship between Dry Matter Increase of Seed and Shoot during the Seed-Filling Period in Three Kinds of Soybeans with Different Growth Habits Subjected to Shading and Thinning

The ratio of dry-matter increase in seed (S) to that in shoot (W), referred to as Rs/W, during the seed-filling period may reflect the balance between the assimilate supply and the sink capacity of harvest organs. In the determinate soybean, cv. Tamahomare, Rs/W during the seed-filling period was nearly the same under various growing conditions including shading and thinning of plants. Therefore, the S in the determinate soybean seems to correlate with the W under various conditions. However, the correlation of the S with the W in indeterminate soybeans in which shoot growth continues during the seed-filling period is unknown. In this study, three soybean cultivars [Glycine max (L.) Merr.], Tamahomare (determinate), Tozan69 (indeterminate) and Peking (semi-indeterminate), were grown under shading and thinning conditions during the seed-filling period. The Rs/w approximated a positive linear regression in the three cultivars. Rs/w was approximately 0.5 in each cultivar. Positive correlations were observed between W and S, pod number or total node number in all cultivars. However, the seed number per pod and individual seed weight were not significantly influenced either by shading or thinning in any cultivar. Hence the rate of partition of assimilate to seeds seems to be determined by pod number. Harvest index was stable except when W was extremely low as when plants were heavily shaded. Our results suggested that the Rs/w, harvest index and the yield-determining processes of the determinate and the indeterminate soybeans are fundamentally the same.

Dynamics of exogenous nitrogen partitioning and nitrogen remobilization from vegetative organs in pea revealed by 15N in vivo labeling throughout seed filling.

The fluxes of (1) exogenous nitrogen (N) assimilation and (2) remobilization of endogenous N from vegetative plant compartments were measured by 15N labeling during the seed-filling period in pea (Pisum sativum L. cv Cameor), to better understand the mechanism of N remobilization. While the majority (86%) of exogenous N was allocated to the vegetative organs before the beginning of seed filling, this fraction decreased to 45% at the onset of seed filling, the remainder being directed to seeds. Nitrogen remobilization from vegetative parts contributed to 71% of the total N in mature seeds borne on the first two nodes (first stratum). The contribution of remobilized N to total seed N varied, with the highest proportion at the beginning of filling; it was independent of the developmental stage of each stratum of seeds, suggesting that remobilized N forms a unique pool, managed at the whole-plant level and supplied to all filling seeds whatever their position on the plant. Once seed filling starts, N is remobilized from all vegetative organs: 30% of the total N accumulated in seeds was remobilized from leaves, 20% from pod walls, 11% from roots, and 10% from stems. The rate of N remobilization was maximal when seeds of all the different strata were filling, consistent with regulation according to the N demand of seeds. At later stages of seed filling, the rate of remobilization decreases and may become controlled by the amount of residual N in vegetative tissues.

How does temperature affect C and N allocation to the seeds during the seed-filling period in pea? Effect on seed nitrogen concentration.

The effect of moderate temperature on seed N concentration during the seed-filling period was evaluated in pea (Pisum sativum L.) kept in growth cabinets and the relation between plant assimilate availability and the variation of seed N concentration with temperature was investigated. Seed N concentration of pea was significantly lowered when temperature during the seed-filling period decreased from a day / night temperature of 25 / 20°C to 15 / 10°C. Our results demonstrate that during the seed-filling period mechanisms linked with assimilate availability can modify seed N accumulation rate and / or seed-filling duration between 25 / 20°C and 15 / 10°C. At the lower temperature (15 / 10°C), an increased C availability resulting from an enhanced carbon fixation per degree-day allowed new competing vegetative sinks to grow as pea is an indeterminate plant. Consequently N availability to filling seeds was reduced. Because the rate of seed N accumulation per degree-day mainly depends on N availability to filling seeds, the rate of seed N accumulation was lower at the low temperature of our study (15 / 10°C) than at 25 / 20°C while seed growth rate per degree-day remains unaffected, consequently seed N concentration was reduced. Concomitantly, the increased C availability at the lower temperature prolonged the duration of the seed-filling period.

Chickpea response to tillage and soil residual nitrogen in a continuous rotation with wheat: II. Soil nitrate, N uptake and influence on wheat yield

A field study was conducted in Córdoba (Spain) on a Vertisol between 1996 and 2001 to determine the effects of tillage system and residual N on spring chickpea N uptake, soil nitrate content and wheat yield in a wheat–chickpea rotation under rainfed Mediterranean conditions. Tillage treatments were no-tillage and conventional tillage. Nitrogen fertilizer rates were 0, 50, 100 and 150 kg ha −1, applied only to wheat. The weather had a marked influence on chickpea N uptake. Total N uptake ranged from 60 to 90 kg ha −1, of which between 42 and 82% was removed by the seed. Total N uptake and seed N uptake were correlated with rainfall during the preceding fallow period and during the flowering and seed-filling period. Straw N uptake decreased with the increase of seed yield. The chickpea crop leaves poor above-ground N residues due to a high N harvest index. Seed N concentration ranged from 3.6 to 4.1%, while straw N levels ranged from 0.8 to 1.4%. The mean N utilization efficiency (NU tE) was 28.4 kg kg −1 (ranging from 11.4 to 22.8) and N harvest index (NHI) was 68% (ranging from 45 to 82%). Chickpea N uptake was directly related to soil nitrate content; it was greater under conventional tillage than under no-tillage, and increased when higher N fertilizer rates were applied to the preceding wheat crop. Overall, the chickpea crop seems incapable of meeting N demands by fixation and does not even supply an equivalent quantity of 50 kg ha −1 of N fertilizer to the following wheat crop.

Chickpea response to tillage and soil residual nitrogen in a continuous rotation with wheat: I. Biomass and seed yield

The present field study was undertaken in Córdoba (Spain) on a Vertisol to determine the effects of tillage systems on spring chickpea ( Cicer arietinum L.) yield over 12 years, and the effects of tillage systems and residual N on chickpea biomass, seed yield and yield components over 4 years, in a wheat ( Triticum aestivum L.)–chickpea rotation under rainfed Mediterranean conditions. Tillage treatments included no-tillage and conventional tillage. Nitrogen fertilizer rates were 0, 50, 100 and 150 kg N ha −1, applied only to wheat. Seed yield was strongly dependent on rainfall during the preceding fallow period, as well as during the flowering and seed-filling period. Maximum seed yield (about 2000 kg ha −1) was achieved with around 390 mm rainfall in those periods. Higher rainfall prompted lower seed yield, due to the negative effect of waterlogging. Although the tillage system did not significantly influence chickpea seed yield, no-tillage represents a viable alternative to conventional tillage. Application of fertilizer N to wheat at a rate of 100 kg N ha −1 consistently influenced subsequent chickpea seed yield due to the carryover effect of fertilizer N. Residual fertilizer N did not appear to affect chickpea N fixation, illustrating the inability of this legume to stock up with N. Biomass and harvest index were the two parameters most closely related to chickpea seed yield. Seeds per pod was the yield component exerting the greatest direct positive influence on seed yield. The compensatory effect of yield components on chickpea yield was very limited, since the indirect effects of these components were negligible.

Shading and Thinning Effects on Seed and Shoot Dry Matter Increase in Determinate Soybean during the Seed‐Filling Period

The relationship between seed and shoot dry matter increase (RS/W) during the seed‐filling period (SFP) can reflect the balance between the assimilate supply and the sink capacity of harvest organs. In a 2‐yr experiment, the RS/W in determinate soybean [Glycine max (L.) Merr.] during SFP was investigated under various growing conditions induced by shading and thinning for plants grown under both standard and reduced densities. The RS/W approximated a positive linear regression in both experiments. Slopes of the lines were less than 0.5 and did not vary within the same year even if plant density was reduced. The shoot dry matter increase (W) hence seemed to directly determine seed dry matter increase (S). A positive relationship between total pod number and W or S was observed in both years. Only minimal changes in seed numbers per pod and individual seed weight were observed, regardless of the treatment applied. A positive relationship also existed between total pod number and the number of branch nodes, and hence W increased S via increase in the number of branch node bearing pods. Half the current assimilate product during SFP appeared to be used for increase of vegetative plant parts. This determined total pod number and hence potential S. Determinate soybean is thus very different from cereal crops, in which almost all the current assimilate during the SFP is appropriated to S. The stability of the harvest index in soybean reflects the important effect of the W on pod establishment during SFP.

Late season nitrogen fertilization of soybeans: effects on leaf senescence, yield and environment

Nitrogen demand from soybean seeds during seed filling is very high and has been proposed as the cause of nitrogen remobilization and leaf senescence. Previous research has not shown consistent effects of late season fertilization on seed yield, while its effects on leaf senescence have not been evaluated. Two field experiments were performed to determine the effects of a late season N fertilization on leaf senescence and fall, seed yield and its components, and residual soil nitrate, and to evaluate the potential risk of groundwater contamination. Two rates of nitrogen (50 and 100 kg N ha−1) were applied at the R3 and R5 development stages. Nitrogen fertilization, either at R3 or R5, increased soil nitrate availability during the seed-filling period. Seed yield, seed number and protein content were not affected by N fertilization. The addition of 100 kg N ha−1 produced a small delay of 1–2 days in the leaf fall, and slightly increased seed size (3.6%). Our results suggest that increasing soil N availability during the seed-filling period is not an effective way to delay leaf senescence or to increase seed growth and yield of soybean. Nitrogen fertilization increased the level of residual nitrate in the top soil at one site (the one with lowest seed yield), increasing the risk of nitrate leaching during subsequent fallow.

Water stress, photosynthesis, seed sucrose levels and seed growth in soybean

The rate of growth of individual seeds of soybean (Glycine max L. Merrill) is determined, in part, by the concentration of sucrose in the seed. Water stress during seed filling reduces photosynthesis, but the effect on seed sucrose concentration is not well understood. Soybean plants (cultivars Elgin 87 and Asgrow 232HS) were exposed to water stress from early in the seed-filling period until maturity in field and greenhouse experiments. Stress reduced yield (5–38%) and seed size (11–35%) but it did not affect the number of seeds. Stress accelerated leaf senescence as shown by a more rapid decline in leaf photosynthesis in both experiments. Seed-growth rate and cotyledon sucrose concentrations (expressed on a mM basis using the bulk water content of the cotyledons) during the linear phase of seed growth were not affected by stress in either experiment. Thus, water stress during seed filling had no direct effect on seed growth; its only effect was to accelerate leaf senescence, which shortened the seed-filling period and resulted in smaller seeds. Strategies to reduce yield loss from water stress during seed filling should focus on leaf senescence instead of seed growth.

Shading and Thinning Effects on Seed and Shoot Dry Matter Increase in Determinate Soybean during the Seed-Filling Period

The relationship between seed and shoot dry matter increase (RS/W) during the seed-filling period (SFP) can reflect the balance between the assimilate supply and the sink capacity of harvest organs. In a 2-yr experiment, the RS/W in determinate soybean [Glycine max (L.) Merr.] during SFP was investigated under various growing conditions induced by shading and thinning for plants grown under both standard and reduced densities. The RS/W approximated a positive linear regression in both experiments. Slopes of the lines were less than 0.5 and did not vary within the same year even if plant density was reduced. The shoot dry matter increase (W) hence seemed to directly determine seed dry matter increase (S). A positive relationship between total pod number and W or S was observed in both years. Only minimal changes in seed numbers per pod and individual seed weight were observed, regardless of the treatment applied. A positive relationship also existed between total pod number and the number of branch nodes, and hence W increased S via increase in the number of branch node bearing pods. Half the current assimilate product during SFP appeared to be used for increase of vegetative plant parts. This determined total pod number and hence potential S. Determinate soybean is thus very different from cereal crops, in which almost all the current assimilate during the SFP is appropriated to S. The stability of the harvest index in soybean reflects the important effect of the W on pod establishment during SFP.

Effects of Sowing Time and Temperature during Seed Filling Period on Yield and Seed Isoflavone Content of Soybean Variety

Effects of Sowing Time and Temperature during Seed Filling Period on Yield and Seed Isoflavone Content of Soybean Variety