LIPOXYGENASE ACTIVITY AND C-6-ALDEHYDE FORMATION IN COMPARISON TO GERMINATION AND VIGOR DURING SOYBEAN SEED DEVELOPMENT

Developmental changes in lipoxygenase (LOX) activity have been observe d during embryo maturation, which suggests that the LOX pathway may be Involved in seed development. A study was designed to measure changes in LOX activity and C-6-aldehyde (hexanal and hexenal) formation duri ng seed development and relate these changes to the attainment of maxi mum germination and vigor. Field grown soybean [Glycine max L. (Merr.) cv. Century] seeds were sampled at regular intervals starting at 31 d after flowering and continuing until maximum dry seed weight [physiol ogical maturity (PM)] in 1990 and 1991. Axes and cotyledons from fresh ly harvested seeds were evaluated for LOX activity and C-6-aldehyde fo rmation. The remaining seeds were air dried and tested for germination and vigor. Maximum germination occurred at 46 and 43 d after flowerin g in 1990 and 1991, respectively. Maximum vigor, as measured by accele rated aging, occurred at 54 and 48 d after flowering in 1990 and 1991, respectively, which was 18 d before PM. During seed development, maxi mum LOX activity occurred in both the axes and cotyledons during the l inear phase of seed growth, but declined before PM. In the axes and co tyledons, maximum hexanal and trans-2-hexenal formation occurred at ap proximately 30% of final dry weight, which was before maximum LOX acti vity, except for axes in 1990. Maximum hexenal and hexanal formation c oincided with the first maximum expression of germination, while maxim um vigor was more closely related to maximum LOX activity in the axes (1991) and cotyledons. Maximum expression of seed quality (germination and vigor) and maximum LOX and C-6-,aldehyde formation were correlate d during soybean seed development.