Effect of Ethephon on the Activity of the Ethylene-forming Enzyme and the Biosynthesis of Ethylene in Winter Rye Seedlings

Abstract

Summary The effect of ethylene-releaser ethephon on the intensity of ethylene production, ACC content, and EFE activity in situ and in vitro (activity of ACC-oxidase) in primary leaves of intact winter rye seedlings was investigated. There were a sharp increase of ethylene production immediately after the treatment and an increase in ACC-oxidase activity in vitro and EFE activity in situ after a lag period of at least 15 min. Inversely, the level of ACC decreased after an equal lag period. Such an effect of ethephon on ethylene biosynthesis was most remarkable 1 to 24 h after the treatment. An additional treatment with 0.1 mM COS0 4 before the application of ethephon inhibited the ethylene production. It is suggested that a major part of the increase in the ethylene production is related to the decomposi- tion of ethephon having penetrated into leaf tissues, while the other part is related to an increased formation of endogenous ethylene from the accessible pool of ACC due to enhanced EFE activity. Treatment with gaseous ethylene (0.8 ppm) caused an increase in ethylene production and a decrease in ACC content. The results reveal an autocatalytic action of exogenous ethylene in intact juvenile tissues and emphasize the probable importance of EFE in a positive regulation of the ethylene formation.