Submitted to: Annals of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2001
Publication Date: 7/6/2001
Citation: Nagel, L., Brewster, R., Riedell, W.E., Reese, R.N. 2001. Cytokinin regulation of flower and pod set in soybeans (Glycine max (L.) Merr.). Annals of Botany 88(1):27-31.
Interpretive Summary: Cytokinins are plant growth hormones that play a role in regulating soybean flower and pod development. A significant percentage of soybean flowers and pods abort before reaching developmental maturity. This abortion leads to a large level of yield loss. A hypothesis has been proposed whereby young distal soybean flowers abort because they cannot compete successfully with the older proximal flowers for limited supplies of nutrients or hormones. Previous studies indicate that there is a strong relation between cytokinin level and regulation of flowering and fruit set in soybean. Although available data show that cytokinins can increase flower and fruit set in individual soybean racemes, they do not clearly show whether these hormones can induce significant changes in the total production of fruits and seeds. The experiments reported in this manuscript were conducted to test the hypothesis that cytokinins act to regulate the distribution of assimilates committed to fruit production.
Technical Abstract: Exogenous application of cytokinin to raceme tissues of soybean (Glycine max (L.) Merr.) Has been shown to stimulate flower production and to prevent flower abortion. The effects of these hormone applications have been ascertained for treated tissues, but the effects of cytokinins on total seed yields in treated plants have not been evaluated. Our objectives were to examine the effects of systemic cytokinin applications on soybean yields using an experimental line of soybeans, SD-87001, that has been shown to be highly sensitive to exogenous cytokinin application. Soybeans were grown hydroponically or in pots in the greenhouse, and 6- benzylaminopurine (BA) was introduced into the xylem stream through a cotton wick for 2 weeks during anthesis. After the plants had matured, the number of pods, seeds per pod, and the total seed weight per plant were measured. In the greenhouse, application of BA resulted in a 79% increase in seed yield compared with controls. Results of field trials showed much greater variability within treatments, with consistent, but non-significant increases in seed number and total yields of about 3%. Data suggest that cytokinin levels play a significant role in determining total yield in soybeans, and that increasing cytokinin concentrations in certain environments may result in creased total seed production.