Regulation of Anthocyanin Synthesis in Apple Skin. II. Involvement of Ethylene

Abstract

Ethylene production by immature apple fruit was stimulated by cycloheximide application, u.v. irradiation and wounding. After fruit were treated with 1 and 10 µg ml-1 cycloheximide, the rate of ethylene production increased to 2 and 10 times the control level, respectively. In skin discs cut from whole fruit (wounded tissue), the rate of ethylene production was stimulated to at least 40 times that in whole fruit. This wound-stimulated ethylene production was partially inhibited by an initial application of cycloheximide. Ultraviolet irradiation of whole fruit stimulated the rate of ethylene production to more than 25 times the control rate after 15 min irradiation. In skin discs, u.v. irradiation caused only a 50-100% increase in ethylene production rate. The effects of certain treatments on ethylene were quantitatively comparable with the effects of the same treatments on anthocyanin formation in whole fruit. Ethylene at 30 µl 1^-1 stimulated anthocyanin in skin of immature apples by 16%. Possible mechanisms by which ethylene may stimulate anthocyanin synthesis are discussed.