Effects of Kinetin , IAA , and Gibberellin on Ethylene Production , and Their Interactions in Growth of Seedlings " 2 Yoram

A bstract. Kinetin in concentrations of 10-e to 10-4 M, stimuated ethylene production in 3 and 4-day old etiolated seedlings of Alaska pea (Pisucm sativum L. var. Ala-ka). Seedlings of other species responded similarly. The response to kinetin depended on the age of the seedlings. Kinetin alone did not influence ethylene production in 6-day old stem sections, but it greatly increased the enhancing effect of IAA. Gibberellic acid had no effect on ethylene production by pea seedlings during the first 6 days of growth. Ethylene and gibberellic acid are antagonistic in their effects on growth of the seedlings; ethylene interfered severely with the action of gibberellic acid but did not completely suppress it. The inhibitors cycloheximide, cupferron, and N-ethylmaleimid?, caused considerable inhibition of kinetin-induced ethylene production but were much less effective in the endogenous ethylene-forming system.