Cytokinin regulation of flower and pod set in soybeans (Glycine max (L.) Merr.)

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 3.4 × 10-7 moles 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 increased total seed production. © 2001 Annals of Botany Company.