Color Stimulation in Attached Apples With Supplementary Light

Attached green apples of seven cultivars exposed to natural prevailing light within the tree canopy supplemented by irradiation for 48 h from cool white fluorescent lamps synthesized anthocyanin. The amount of anthocyanin synthesized was correlated with the added incident energy, except when the low temperatures necessary for anthocyanin synthesis in the cultivars McIntosh, Cortland and Northern Spy did not occur. The minimum energy requirement for anthocyanin synthesis varied considerably with cultivar and changed during the season. The anthocyanin content of fruits at harvest was correlated with their potential to produce anthocyanin during the growing season.