Oskar Schmidt

Plant Growth Retardants as Inhibitors of Ethylene Production

Summary Plant growth retardants of the norbornanodiazetine (tetcyclacis) and triazole (BAS 111 W) types inhibited ethylene production in leaf discs of barley and oilseed rape. The maximal reduction of 70 % was reached 5 h after treatment. The addition of gibberellic acid could not overcome the effects. At concentrations of the retardants up to 3 x 10-4 mol x 1-1 the reduction in ethylene formation was accompanied by increased or nearly constant levels of 1-aminocyclopropane-l-carboxylic acid (ACC) and N-malonylACC in the leaf discs. This suggests an inhibition of the conversion of ACC to ethylene in the biosynthetic pathway. As explanations a direct influence on the ethylene-forming enzyme or an indirect effect via a retardant-caused modification in the cellular membrane properties are discussed.