Temperature Regulation of Anthocyanin Accumulation in Apple Skin

Abstract

The regulation of anthocyanin accumulation in apple skin (cv. Jonathan) by temperature was studied. In the field the increase in anthocyanin in the skin before harvest coincided with decreasing temperatures and with increasing ethylene production by the fruit. In detached apples held under continuous white light, the optimum temperatures for anthocyanin accumulation were 12 °C in unripe apples and 16–24 °C in ripe apples. These effects were explained by corresponding changes in the level of phenylalanine ammonia-lyase (PAL), a key enzyme of flavonoid synthesis. PAL levels were higher at low than at high temperatures and higher in ripe than in unripe apples. In intermittent light the effects of temperature were similar but levels of PAL and anthocyanin were lower, particularly in unripe apples. It is concluded that temperature, in conjunction with ripening and light, is an important factor regulating anthocyanin accumulation and that its effects are mediated by effects on the level of PAL activity.