Control of Dry Matter Accumulation in Soybean Seeds1

Seed development was characterized for greenhouse‐grown soybean genotypes [Glycine max (L.) Merr.] representing 12 selections differing in petiole diameters and 12 selections differing in seed size. The objective was to evaluate regulation of dry matter accumulation by seeds. Sucrose release rates per square meter (SRRA) and per seed coat (SRRT) from opened seed coats into 0.2 M sorbitol, adjusted for sucrose exudate from cut pod walls, and dry matter accumulation rates per seed (DMAR) were selected to characterize seed development. Six measures, selected as ✕ variables, were grouped into two sets of closely correlated variables: Group 1 (petiole area and leaf area) and Group 2 (area of seed‐coat cup, seed‐coat area, weight per seed, and seed number). Highly significant differences were found among genotypes for SRRA, SRRT, and DMAR. The DMAR variability among genotypes was explained by the regression of DMAR on the six ✕ variables with Group 2 variables being of primary importance. The DMAR per unit seed‐coat area or per plant were similar among groups of genotypes differing in seed size. The SRR measures were associated with Group 1 variables with petiole area being most important. The SRRA measure was also associated with leaf area. The SRR measures and DMAR were not associated. The SRR measures reflected (presumed) transport capacity with no tie to the control of DMAR. No evidence was found using this technique, for a control operating at the seed‐coat level that affected SRR and DMAR. Dry matter accumulation rates per plant reflected primarily a genetically controlled balance operating at a level other than the seed.