Biochemical characterization of soybean ovary growth from anthesis to abscission of aborting ovaries.

Soybean (Glycine max [L.] Merr.) ovary growth was measured from anthesis to 6 days after anthesis (DAA) to establish a timetable of biochemical events that might be useful in identifying processes that initiate abscission. Two procedures were developed to provide samples with either high or low percent pod set for ;IX93-100,' a semideterminate line having long racemes. Characteristics measured were fresh and dry weight, soluble and insoluble protein, soluble carbohydrate, starch, RNA, and DNA. Setting ovaries grew more rapidly than abscising ovaries. Since there was a daily increase in ovary weight in both groups, all measured characteristics showed daily increases when expressed on perovary basis. Statistically significant differences between groups were detected between 2 and 5 DAA for most characteristics. When chemical composition was expressed on concentration basis, starch level was significantly higher in setting ovaries at 5 and 6 DAA. Regression analysis showed that these deviations between setting and abscising samples started between anthesis and 1 DAA. We conclude that processes leading to eventual shedding of fertilized ovaries (called flower abortion in soybeans) commence soon after anthesis of the shed flower, and that setting and abscising ovaries do not differ in protein, soluble carbohydrate, starch, or nucleic acid content when abscission processes begin.