Seed Fill Duration Research Articles

Cold Stress Injury during the Pod‐Filling Phase in Chickpea (Cicer arietinum L.): Effects on Quantitative and Qualitative Components of Seeds

AbstractChilling stress (<10 °C) is detrimental for chickpea, especially at the reproductive phase and leads to abortion of flowers, pods and impaired seed filling, causing severe reduction in yield. The information on the effects of low temperature during different pod‐filling stages on quality and quantity of developing seeds is lacking in chickpea and hence this study. In this study, chickpea plants growing under warm conditions of the glasshouse were subjected to cold conditions of the field at the two stages, (a) early pod‐filling and (b) late pod‐filling, and subsequently analysed for stress injury in terms of electrolyte leakage (EL), 2,3,5‐triphenyl tetrazolium chloride reduction, relative leaf water content and total chlorophyll content in the leaves of control and cold‐stressed plants. Cold stress caused elevation of EL but reduced all the other parameters. Sucrose content decreased significantly in the leaves of cold‐stressed plants. The differences between the effects of stress at two stages on the total plant dry weight were small and insignificant. The seed growth rate, seed fill duration, seed number, and average seed weight and size decreased greatly in the plants cold‐stressed at the late pod‐filling stage than those stressed at the early pod‐filling stage. Greater reduction was observed in starch, proteins, soluble sugars, fat, crude fibre and storage protein fractions in the seeds of the plants cold‐stressed at the late pod‐filling stage. This coincided with a larger decrease in sucrose content, the activities of sucrose synthase, invertase and starch synthase observed at this stage. The germination and growth potential were, however, inhibited to a greater extent in seeds of plants stressed at the early pod‐filling stage.

Ectopic expression of phosphoenolpyruvate carboxylase inVicia narbonensisseeds: effects of improved nutrient status on seed maturation and transcriptional regulatory networks

Seed maturation responds to endogenous and exogenous signals like nutrient status, energy and hormones. We recently showed that phosphoenolpyruvate carboxylase (PEPC) overexpression in Vicia narbonensis seeds alters seed metabolism and channels carbon into organic acids, resulting in greater seed storage capacity and increased protein content. Thus, these lines represent models with altered sink strength and improved nutrient status. Here we analyse seed developmental and metabolic parameters, and C/N partitioning in these seeds. Transgenic embryos take up more carbon and nitrogen. Changes in dry to FW ratio, seed fill duration and major seed components indicate altered seed development. Array-based gene expression analysis of embryos reveals upregulation of seed metabolism, especially during the transition phase and at late maturation, in terms of protein storage and processing, amino acid metabolism, primary metabolism and transport, energy and mitochondrial activity, transcriptional and translational activity, stress tolerance, photosynthesis, cell proliferation and elongation, signalling and hormone action and regulated protein degradation. Stimulated cell elongation is in accordance with upregulated signalling pathways related to gibberellic acid/brassinosteroids. We discuss that activated organic and amino acid production leads to a wide-range activation of nitrogen metabolism, including the machinery of storage protein synthesis, amino acid synthesis, protein processing and deposition, translational activity and the methylation cycle. We suggest that alpha-ketoglutarate (alpha-KG) and/or oxalacetate provide signals for coordinate upregulation of amino acid biosynthesis. Activation of stress tolerance genes indicates partial overlap between nutrient, stress and abscisic acid (ABA) signals, indicating a common interacting or regulatory mechanism between nutrients, stress and ABA. In conclusion, analysis of PEPC overexpressing seeds identified pathways responsive to metabolic and nutrient control on the transcriptional level and its underlying signalling mechanisms.

A water deficit during pod development in lentils reduces flower and pod numbers but not seed size

An experiment was conducted under controlled conditions in a glasshouse to determine the sensitivity of reproductive development of lentil (Lens culinaris Medikus) genotypes of different origins to water deficit. The 3 genotypes were Cassab (West Asia), Simal (South Asia), and ILL 7979 a crossbred between a West Asian genotype and a South Asian genotype. Two watering treatments, a well-watered control and a water-deficit treatment, were imposed from the beginning of podding. Leaf water relations, total dry matter production, leaf area, and number of flowers, pods, and seeds were measured from podding to maturity. In the well-watered plants the leaf water potential (ψleaf) before sunrise ranged from −0.6 to −0.8 MPa. When subjected to water deficit, ψleaf fell to about −3.0 MPa. Genotypes did not show variation in vegetative growth or seed yield under either well-watered or water-deficit conditions, but they differed significantly in the number of flowers, fruiting nodes, pods, and seeds, and harvest index (HI). Seed size in Cassab was 61% larger than ILL 7979 and 105% larger than Simal. The small-seeded genotypes produced the highest number of fruiting nodes and hence a greater number of flowers, pods, and seeds. Seed size was positively correlated with seed growth rate (r = 0.77**) and seed fill duration (r = 0.45*). The water deficit reduced plant height by about 20%, leaf area by 48–81%, and total dry matter by about 60% compared with well-watered plants. The water deficit reduced flower number by 35–46% and increased seed abortion (empty pods) by 17–46%. The water deficit had no effect on the maximum seed growth rate, seed fill duration, or final seed size in any of the 3 genotypes. Therefore, the 70% reduction in seed yield induced by the water deficit was primarily due to a reduction in pod and seed numbers (by 59–70%) rather than individual seed growth rate and seed size.

The role of seed in the determination of yield of grain crops

The seed is the harvested organ in grain crops and, consequently, the accumulation of dry matter by the seed is an important component of the yield production process. The growth of individual seeds, usually characterised by the rate and duration of growth, is, at least partially, controlled by the seed itself. It is this control that gives the seed a significant role in the yield production process. Genetic variation in seed growth rate, which is substantial, is not related to yield, but variation related to environmental conditions during seed filling often is. Genetic and environmental variation in seed-fill duration is usually directly related to yield. Much is now known about the regulation of seed growth and this knowledge, if applied, may help answer some of the important questions still facing crop scientists as they try to increase yields in the future.

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.

Control of storage protein accumulation during legume seed development

Summary The regulation of partitioning of carbohydrate skeletons into different storage products of developing seeds is still not understood. We explored two ways to gain more insight in the process. First we analyzed mechanisms that control storage protein accumulation in Vicia faba seeds of contrasting protein content. As expected, the seeds of the high protein genotypes (HP) contained more protein and total nitrogen as compared to the low protein genotypes (LP) whereas starch and total amounts of carbon were not altered. There was no major difference in the proportion of amino acids delivered from seed coats into the endospermal cavity of either HP or LP genotypes. However, HP genotype cotyledons contained two-fold higher levels of free amino acids at the later developmental stages when their higher protein content was expressed. After four hours of incubation, in vitro uptake rates of 14 C glutamine by HP cotyledons were significantly higher for the protein rich cotyledons indicating a possible higher capacity to take up amino acids. In both genotypes 14 C-glutamine was rapidly converted into glutamate and then partly decarboxylated to γ-amino butyric acid. However, in the HP cotyledons the ratio of 14 C-glutamine to 14 C-glutamate was higher as compared to the LP cotyledons reflecting the observed higher glutamine uptake rate. In a second approach we studied Vicia narbonensis seeds which expressed ADP glucose pyrophosphorylase in antisense orientation. These seeds contained less starch and more sucrose and water but also more protein. In addition, blocking the starch synthesis pathway caused pleiotropic effects on water content and induced temporal changes in seed development. The resulting longer seed fill duration period could partially explain the observed elevated protein content in the AGP-antisense seeds.

Phenological Development–Yield Relationships in Dry Pea in Semiarid Mediterranean Conditions

Dry pea (Pisum sativum L.) growers in the semiarid Mediterranean region require cultivars that are both early maturing and high yielding. However, negative relationships between these two characteristics limit their simultaneous improvement. A better understanding of the relative importance of the developmental stages in determining yield would assist in pea improvement. Sixteen dry pea cultivars were grown for 2 years under semiarid Mediterranean conditions (Maru, north Jordan) in order to see if differences in growing degree days (GDD) to flowering and GDD from planting to physiological maturity exist and to study their relationships with seed yield. Seed yield was negatively correlated with GDD to maturity, but not significantly correlated with GDD to flowering. Increasing GDD to flowering resulted in higher seed yield, while increasing seed fill duration had little effect. Rapid seed fill rate was positively correlated with seed weight and negatively correlated with seed fill duration. These results indicate that Mediterranean‐adapted cultivars would have preflowering periods lasting as long as possible, followed by short seedfill periods. Simultaneous selection for early maturity and a relatively long time to flowering is recommended for the development of early‐maturing, high‐yielding cultivars adapted to semiarid Mediterranean environments.

Drought and nitrogen source effects on nitrogen nutrition, seed growth, and yield in soybean

Abstract Drought in soybean [Glycine max (L.) Merr.] decreases yield‐related processes and N2 fixation is more sensitive to drought than are many other of these processes. Therefore, application of nitrogen (N) fertilizer may increase drought tolerance over those plants primarily dependent on N2 fixation. In a field experiment, NH4NO3 applications (+N) to drought‐stressed soybean resulted in biomass and N accumulation rates similar to those rates for an irrigated treatment without N fertilizer (‐N). In contrast, biomass and N accumulation rates were decreased for the ‐N treatment. N fertilization increased seed growth rate and decreased seed fill duration for irrigated and drought treatments. In the drought treatment, N application increased seed number per unit area, which resulted in higher yields. In a greenhouse experiment, fertilization with either KN03 or NH4C1 increased biomass and N accumulation rates during drought over those of plants dependent solely on N2 fixation. It was concluded that application of N fertilizer to soybean increases drought tolerance because of the extreme sensitivity of N2 fixation to drought.

Phenology, growth, and yield of field-grown soybean and bush bean as a function of varying modes of N nutrition

In field trials conducted at four sites in Hawaii, soybean ( Glycine max) and bush bean ( Phaseolus vulgaris) were either inoculated with homologous rhizobia, fertilized at high rates with urea, or left unamended. Crop phenology was assessed every few days. Rates of biomass and N accumulation and components of yield were measured five times during each crop cycle to assess the extent to which: (i) crops relying on soil, symbiotic, or fertilizer N differed in their growth characteristics; (ii) mode of N nutrition affected the timing of developmental stages; and (iii) effects of N nutrition on crop growth and development were related to final yield. While all measured variables differed significantly between sites, the effect of changing N source on these variables, in N limited environments, was consistent across sites. Rate and extent of node production, crop growth and yield were increased in symbiotic and N-fertilized crops as compared to unamended, non-fixing crops, while reproductive development was protracted. Extended time required to reach reproductive maturity was attributable to an increase in seed fill duration as time to flowering was not affected. Development and yield of N 2-fixing crops were similar but not equivalent to those of N-fertilized crops. To produce reliable yield estimates, legume growth simulation models must be able to accurately simulate crop growth and phenology. The present data indicate that information relating to source and supply of N must be incorporated before such models can be used to generate reliable yield estimations. Results of these trials also provide a valuable dataset for calibrating model subroutines for inorganic nitrogen uptake and nitrogen fixation in soybean and bush bean growth under field conditions and adjusting model coefficients for tropical environments.

Soybean Yield Interaction between Helicoverpa zea Infestation and Simulated Frost Injury

AbstractSoybean, Glycine max (L.) Merr., yields may be reduced by corn earworm, Helicoverpa zea (Boddie), feeding and by early frosts. One consequence of H. zea feeding can be a delay in pod development. A consequence of frost injury can be shortening of the seed fill duration. The objective of 12 experiments conducted at multiple locations from 1984 to 1987 was to evaluate the potential for an interaction between H. zea feeding damage and early frost. Insecticides were used to establish varying levels of H. zea populations in soybean and paraquat (1,1′.dimethyl‐4,4′‐bipyridinium dichloride) was used to simulate frost injury. Significant yield differences between levels of H. zea populations were detected in eight experiments, and paraquat treatments significantly reduced yields in 11 experiments. A significant interaction between H. zea population level and paraquat treatment time occurred in three experiments. In these experiments, yield reduction due to paraquat was greater where H. zea populations were larger. Although soybean can compensate for a delay in pod set caused by H. zea feeding in most years, when seed fill period is shortened, as would occur with early frost, a delay in pod set can contribute to yield loss. Identifying one of the many factors that lead to variation in yield loss from a particular level of H. zea infestation, is a step towards more effective management of this pest.

Phenotypic Recurrent Selection for Modified Reproductive Period in Soybean

Seed‐filling duration has generally shown a positive association with seed yield in soybean [Glyelne max (L.) Merr.], but results have been inconsistent among studies. Four phenoWpic recurrent selection programs were completed, increased flowering.period duration (FPD) vs. increased seed‐filling duration (SFD) and long vs. short reproductive period duration (RPD), with the objective of investigating the effects of these modifications on seed development and seed yield. Selection for average physiological maturity (RT) maintained R7 maturities among populations. Selection for increased RPD through FPD or SFD increased genetic correlations between reproductive stages. The major responses to selection occurred in the first cycle due in part to the 3‐yr evaluation, but high correlations between stages also restricted progress. Manipulating RPD modified primarily FPD. The SFD seemed to have a minimum threshold, but responded to selection pressure. Divergent selection for RPD created a 10‐d difference in RPD, but the selection had minimal effects on seed yield potential. The soybean has the capacity to achieve seed yield independent of changes in duration of reproductive stage. Increasing RID through increased SFD within a broad‐base population had an associated increase in seed set and in seed yield for a set of favorable environments, but this yield advantage was not expressed for a set of environments with drought stress during the reproductive period. Increased SFD was associated with increasing potential number of seed set and, as has been shown, decreasing assimilate uptake rate. Selection for increased SFD would be important for populations where SFD could be limiting. The effects of modifying seed‐filling duration are not clear‐cut, but manipulating facets that affect it can create unacceptable responses.

Mobilization of leaf N in soybean genotypes with varying durations of seedfill

Soybean ( Glycine max (L.) Merrill) genotypes differing in seedfill duration were grown in the field for two years to characterize the mobilization of leaf N during fruiting. The duration of seedfill was estimated as the time from growth stage R5 (beginning seedfill) to R7 (physiological maturity) and as the effective filling period (EFP) calculated from seed growth rate and final seed mass estimated from seeds in fruits tagged at the beginning of seedfill. Nitrogen was measured in the last fully expanded leaf on the main stem at weekly intervals during seed development. There were significant genotypic differences in both estimates of the duration of seedfill in both years. The length of the R5 to R7 period ranged from 18 to 48 days in 1983 (7 genotypes) and from 30 to 52 days in 1984 (8 genotypes). The range in EFP across all genotypes was 17–40 days in 1983 and 16–35 days in 1984. Leaf N concentration declined steadily during seedfilling, reaching a minimum level of approximately 2.0–2.5% at R7. The leaf N concentration declined more rapidly in genotypes with shorter durations of seedfill; however, when leaf N concentration was expressed as a function of the stage of seed development the changes in leaf N were constant across genotypes. The data indicate that the long-filling-period characteristics was associated with a slower rate of leaf senescence rather than with a later initiation of senescence.

Effects of planting date on seasonal patterns of nitrogen assimilation and partitioning by two soybean cultivars

Abstract Delayed planting consistently reduces grain yields by soybeans [Glycine max (L.) Merr.]. Grain yield of soybeans is thought to be influenced by the duration of seedfill which in turn is influenced by remobilization of N from vegetative tissue. A field study was conducted during two growing seasons in Urbana IL. to evaluate the effect of planting date on N accumulation, partitioning, and remobilization by soybean cultivars ‘Williams 79’ and ‘Corsoy 79’. Soybeans were planted in mid‐May or mid‐June of 1982 and 1983. Tissue samples including abscised material, were collected at R1, R5, R7, and R8 and separated into seeds, pods, stems, leaflets and petioles for N analysis. Kjeldahl plant N prior to seedfill was generally greater in Williams 79 than Corsoy 79; however, the latter stored more N per unit biomass to partially compensate for reductions in total biomass. Cultivar differences in vegetative N were more pronounced with delayed planting. Water stress during 1983 reduced total leaf N levels at ...

Nitrogen Partitioning and Dry Matter Allocation in Soybeans with Different Seed Protein Concentration1

Physiological studies of soybean (Glycine max L. Merr.) genotypes with wide differences in seed protein concentration may permit detection of important yield‐related processes. Crop growth analyses were performed in 1977 and 1980, at Gainesville, FL, on seven and eight near homozygouds eterminates oybean genotypes, respectively. In 1977, the relationships between yield, seed protein concentration, and the visual length of seed filling were also studied in 23 genotypes. The purpose of this work was to characterize N partitioning and dry matter allocation to seed, and their association with yield and other characteristics. Soybean genotypes with a range in seed protein concentration of approximately 0.38 to 0.50 kg/kg were used. Nitrogen partitioning to seeds was estimated as the change in Harvest Nitrogen Index (HNI), the ratio of seed N weight shoot N weight (disregarding fallen leaves) with time, from beginning linear seed growth until maturity. Nitrogen partitioning in high seed protein genotypes was positively associated with their higher seed N demanda nd faster or earlier vegetative N depletion. In both years, Harvest Index (HI) estimated as the ratio of seed dry weight to shoot dry weight (disregarding fallen leaves) increased linearly with lime in all genotypes from the beginning of linear seed growth until maturity (R8). The Dry Matter Allocation Coefficient (DMAC), an estimate of the rate of dry matter allocation to seed, is defined as the derivative of HI with respect to time, during the linear phase of HI increase. Thus, DMAC is a constant for each genotype‐environment combination. Dry Matter Allocation Coefficient exhibited less variability than Seed GrowthR ate estimated on a land area basis (CV = 6.8 vs. 21.8%). In both years, DMAwCa s positively associated with seed protein conten~ and faster vegetative dry weight decline during seed filling, and negatively associated with seedfilling duration, and yield. Yield was positively associated with seed‐filling duration (RS‐R7), and negatively associated with seed protein concentration. Thus, in general, high seed protein genotypes exhibited faster N partitioning and dry matter allocation into seeds, shorter seed‐filling duration, and lower yield.

Genotypic Variation for Duration of Seedfill in Soybean1

The length of the seed filling period is related to yield in soybean [Glycine max (L.) Merr.] and may be useful as a selection criterion in cultivar development programs. Genotypes from the World Soybean Germplasm Collection were grown in the field at Lexington, Ky. to estimate the genotypic variation in seed filling period that is available and to compare methods of estimating the seed filling period. Nine (1980), 14 (1981), and 59 (1982) genotypes were grown in four‐row plots 6 m long with 0.76 m between rows with two replications using conventional cultural practices. The length of the seed filling period was estimated from whole plant growth stages (R4 to R7 and R5 to R7) and from the effective filling period (EFP) determined from individual seed measurements. Significant genotype differences were found each year for all estimates of the filling period; however, genotypes with filling periods significantly longer than the longest filling period of a check cultivar were identified only in 1982. There was a significant genotype ✕ year interaction for 13 genotypes in the test for 2 years. The interaction seemed to result from the differential effects of moisture stress on the seed filling periods of the unadapted genotypes. There was a consistent relationship between the growth stage estimates of seed filling period and EFP over all genotypes and across 2 years; however, late maturing check cultivars (MG IV and V) showed longer filling periods, based on growth stage estimates, than MG III check cultivars; but there were no significant differences in EFP. The genotypes with long filling periods could be useful in developing higher yielding soybean cultivars, even though significant genotype ✕ year interactions frequently occur.

Analysis of the Carbon and Nitrogen Limitations to Soybean Yield1

AbstractSoybeans are hypothesized to be “self‐destructive” since they apparently need to translocate large amounts of nitrogen from vegetative tissues during seed‐fill to sustain seed growth. To assess the possible limitations of this characteristic on soybean seed yield, a simple, dynamic simulation model is developed which accounts for the availability of nitrogen and photosynthate within the plant. The simulations show that the duration of seedfill and seed yield is clearly limited by the self‐destructive characteristic. Increased availability of nitrogen within the plant is required for significant increases in soybean yields. Possible alterations of the model required to mimic actual soybean seed growth are presented.