Influence of Ethephon on Soybean Reproductive Development1

Increased incidence of flower and young pod abscission occurs in soybean [Glycine mar (L.) Merr.] when subjected to environmental stresses, but the induction stimulus of the abscission process has not been investigated. The objective of this study was to investigate the role of ethylene on soybean reproductive development. Whole soybean plants were treated in a growth chamber with increasing rates of ethephon [(2‐chloroethyl) phosphonic acid] (an ethylene releasing chemical) at selected growth stages and ethylene release from treated tissue was monitored. The ethylene generated from ethephon was then investigated for effects on flower shedding and on pod and seed development. Also, selected plant tissue was monitored for ethylene release when subjected to stresses induced by excission. The results indicate that tissue ethylene level was elevated comparable to the amount of ethephon applied. Also, as the amount of ethephon was increased, the longer the tissue ethylene level remained elevated. Ethephon increased flower shedding when applied at rates of 100 mg L−1 or higher. However, only the 1000 mg L−1 rate had extreme detrimental effects on seed and pod development. Excised leaf and reproductive structures evolved ethylene in response to stresses induced by excision. The results demonstrate that ethylene can induce reproductive structure abscission, and stress can trigger ethylene biosynthesis in soybean.