Partitioning of Assimilate Between Vegetative and Reproductive Growth in Soybean1
- D. B. Egli,
- R. D. Guffy and
- J. E. Leggett2
Changes in the proportion of the total biomass harvested have made an important contribution to the increase in yield in several grain crops. Field experiments were conducted for several years on Typic Argiudoll and Typic Paleudalf soils to investigate the effect of cultivars, growth habit, and environmental conditions on the partitioning of assimilate between vegetative and reproductive plant parts in soybean [Glycine max (L.) Merr.] during flowering and fruit set. The experiments included the following variables; cultivars from maturity group I1 to V, including both indeterminate and determinate growth habits, optimum and delayed plantings, and moisture stress. Data were collected from growth stage R1 to R6 on vegetative growth characteristics (nodes on main stem, total nodes, and plant height), pod development, and weight of vegetative and reproductive plant parts. Partitioning coefficients were calculated by dividing fruit weight by the total aboveground biomass. The nodes on the main stem and on the branches reached a maximum at R5 in all cases. Determinate cultivars produced fewer nodes on the main stem between R1 and R5; however, they produced more branch nodes and the total node production was greater than the indeterminate cultivars. The number of pods containing developing seed increased until approximately R6, suggesting that the production of new vegetative sinks (node production) in soybean stopped before the total fruit load was established. The partitioning coefficients increased rapidly from < 5% at growth stage R3 to ≥ 30% at R6. The partitioning coefficient at any growth stage varied only slightly across the variables included in the experiments. This suggests that variation in fruit and seed number may be more closely related to variations in crop growth rate than to variations in the allocation of assimilate between vegetative and reproductive plant parts.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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