Induction of Ethylene Production by Rape Seed Oil and Ethanol in Fig and Persimmon Fruits

Abstract

The mechanism which induces the ethylene evolution in the fig 'Masui-Dauphin' and Japanese persimmon 'Hiratanenashi' was investigated by treating the fruits with rape seed oil and ethanol.
The rape seed oil, which was injected through ostiolum of the fig fruit harvested at preclimacteric stage, induced a rapid ethylene evolution, similar to that obtained by treatment with exogenous ethylene. In oil-treated fruits, the activity of ethylene forming enzyme (EFE) increased markedly, attaining a level about 12 times that of control after 24 hr, but 1-aminocyclopropane-1-carboxylic acid (ACC) level increased gradually. The application of 2, 5-norbornadiene, a competitive inhibitor of ethylene action, inhibited both EFE activity and ACC accumulation, which led to a significant suppression of ethylene production within 48 hr of the oil treatment. Ethylene production induced by oil was almost competitively inhibited by aminooxyacetic acid (AOA), an inhibitor of ACC synthase. The ethylene production by persimmon fruit slices was also induced by infiltrating oil into the tissue, but this treatment was less effective as compared to responses observed in the fig.
Ethanol vapors induced rapid ethylene evolution in the fig and persimmon fruits which were harvested at a preclimacteric stage. In the fig, EFE activity increased to a maximum level with vapor concentrations of 0.5 and 1.0 ml ethanol per 100 g fresh fruit weight, but the. activity decreased with continuous increases in ethanol concentration. The flesh ACC content, however, tended to increase with much higher ethanol concentration. Ethylene production induced with ethanol was almost competitively prevented by AOA.
These data suggest that the inducing effect of oil and ethanol on ethylene production in the fig and persimmon fruits is likely the result of a biochemical stress which activates the ACC-ethylene biosynthesis system.