Effects of External Ethylene on the Production of Endogenous Ethylene in Olive Leaf Tissue

Abstract Olive ( Olea europaea L.) leaves are characterized by their ability to respond to exogenous ethylene by a 100- to 400-fold enhanced ethylene production irrespective of leaf age or time of year when sampled. The autoenhancement of ethylene production from intact or detached leaves is positively correlated with the concentration of external ethylene. A lag time of 72 to 120 hr occurred before the autoenhancement of ethylene production could be observed. An autoinhibition of ethylene production was usually observed during the first 24 to 48 hr. The effect was, however, much less pronounced. This autoinhibition of ethylene production apparently does not involve wound ethylene. Olive fruit normally produce only negligible amounts of ethylene, and the enhanced ethylene evolution, which was observed after the fruits were exposed to exogenous ethylene, was found to be exogenous ethylene that was trapped by the fruit tissue during its exposure to ethylene. In leaves, however, autoenhancement of ethylene production evidently is a physiological response that may induce a senescing process in the leaves rather than abscission.