Ethylene Evolution following Treatment with 1-Aminocyclopropane-1-carboxylic Acid and Ethephon in an in Vitro Olive Shoot System in Relation to Leaf Abscission

Abstract

1-Aminocyclopropane-1-carboxylic acid (ACC) supplied via the cut base of detached olve shoots caused a burst of ethylene from leaves, but other cyclopropanes tested did not exhibit this effect. Ethephon (ET) and another ethylene-releasing compound caused a prolonged increase in ethylene evolution. ACC had only a very lmited effect on leaf abscission regardless of concentration, whereas shoots placed with cut bases in ET for 60 to 80 minutes exhibited 100% leaf abscission within 90 hours. Shoots with Inflorescences treated with ET just prior to anthesis began to wilt in vitro withn 20 to 30 hours and failed to exhibit leaf abscission. At earlier stages of devebpment, ET induced more leaf abscission on reproductive shoots than on vegetative shoots. It is suggested that the duration of ethylene evolution from the leaves governs their potential for abscission and that bursts of ethylene evolution even though large in amount may not induce abscission.