Effects of 'Tree Ethylene Inhibitory Factors' on Fruit Drop and Ethylene Production in Persimmons

Abstract

　The concept that fruits on a tree receive ethylene - inhibitory factors ('tree factors') transported from leaves has been supported by several studies. In the present study, the fruit drop and internal or endogenous ethylene synthesis in young 'Hiratanenashi' persimmons were promoted markedly by the leaf - shading or defoliation of fruit - bearing shoots, which supported the existence of 'tree ethylene - inhibitory factors'. The infiltration of a crude leaf extract (extracted in ethanol and dissolved in phosphate buffer), and three leaf - extract fractions of different polarities (hexane, ethyl acetate, and aqueous fractions, and four plant hormones (ABA, GA₃, IAA, and zeatin) into fruit flesh did not inhibit endogenous ethylene production in detached young 'Hiratanenashi' persimmons, and thus the leaf extracts contained none of the expected 'tree ethylene - inhibitory factors'. Thus, some kind of physical action, for instance water supply, rather than substances in the leaves may act as one of the 'tree ethylene - inhibitory factors' in persimmons.