The Effect of Source-Sink Alterations on Soybean Seed Growth*

Abstract

Soybeans (Glycine max L. Merrill) were grown in the greenhouse and in the field to investigate the effect of variations in the assimilate supply during the linear phase of seed development on the rate and duration of growth of individual seeds. Increased assimilate supplies, created by partial fruit removal, increased rates of dry matter accumulation, duration of seed growth, and final seed size (weight per seed). Reductions in the supply of assimilate to the developing seed, created by shading (60 per cent) the plants during the linear phase of seed development, lowered seed growth rate but did not affect final seed size because of a longer duration of seed growth. Nitrogen stress during seed development, created by removing N from the nutrient medium, did not affect seed growth rate but shortened the duration of seed growth and reduced final seed size. The data indicate that the growth characteristics of soybean seed are influenced by the supply of assimilate to the seed during the linear phase of seed development.