Aharoni, N., Dept of Fruit and Vegetable Storage, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel

The antagonistic effects of ethylene and Ag+ on the metabolism of [1‐14C]indole‐3‐acetic acid (IAA) and on the rates of ethylene production were studied in tobacco leaf discs (Nicotiana rustica var. Brasilia). During the first 10 h of incubation, Ag+‐pretreated leaf discs contained more free [14C]IAA than untreated ones due to decreased oxidative decarboxylation, and the discs also produced more ethylene. Exogenously supplied ethylene nullified these effects of Ag+. However, the most pronounced effect of Ag+ in increasing ethylene production, as well as the strongest antagonistic effect of exogenous ethylene, were found between 24 and 48 h of incubation. During this time span no effect on the level of free IAA and on its decarboxylation could be observed. It is suggested that ethylene exerted its autoinhibitory effect by a feedback control on the IAA‐induced ethylene biosynthesis. Possible mechanisms for the autoinhibitory effect of ethylene are discussed. Copyright © 1985, Wiley Blackwell. All rights reserved