Photoregulation of Anthocyanin Synthesis in Apple Fruit under UV-B and Red Light

The involvement of photomorphogenic photoreceptors in anthocyaninsynthesis was investigated in apple fruits under UV light from280 to 320 nm (UV-B) and red light (R). Short-term R treatmentwas ineffective in the induction of anthocyanin synthesis butthe involvement of phytochrome was indicated by the resultsof long-term irradiation (18 h) with R. The inductive effectof 18 h UV-B on anthocyanin synthesis was stimulated synergisticallyby subsequent irradiation with R for 15 min, and the R, far-redlight (FR) photorevesibility of this effect indicated the involvementof phytochrome in this synergism. The effect of UV-B on anthocyaninsynthesis was not influenced by subsequent irradiation withFR, suggesting that the effect of UV-B was independent of phytochrome,and that a specific photoreceptor for UV-B was involved. WhenR was given simultaneously with UV-B (18 h), anthocyanin wassynthesized at a much higher rate than it was after sequentialirradiation with UV-B and R. Photosynthesis was shown to beinvolved inthis synergistic increase in the synthesis of anthocyanin,although the involvement of phytochrome in the expression ofthis response, at least in part, was suggested by a reductionin the rate of anthocyanin synthesis by FR. (Received March 14, 1988; Accepted September 28, 1988)