The relationship between levels of anthocyanin and those of other constituents such as total phenolics, sugars, organic acid, and endogenous hormones in the skin and pulp of ripening grapes was studied during the period from veraison to full maturation under the two different temperature conditions for fruit clusters at 10℃ and 30℃.
The accumulation of antkocyanin in ´Kyoho´ berry skin was inhibited when exposed to 30℃ but it was greatly increased at 20℃. The content of total phenolcs in berry skin increased rapidly 3 weeks after exposure to 20℃, but showed slight increase at 30℃. The concentration of ABA in fruit skin and pulp was increased one week after the temperature treatment, and significantly higher concentration of ABA were determined in samples at 20℃ than in those at 30℃ at all sampling dates. Cytokinin activity in berry skin and pulp decreased gradually when treated at 20℃, but increased at 30℃ as ripening progressed. The activities of auxin and GA in berry skin and pulp was not different significantly between the temperature treatments.
The results suggest that fruit temperature have direct effects on the coloration of ´Kyoho´ grape fruit, and that ABA content is likely to be the main factor affecting coloration but further study needs to elucidate its detailed mechanism.
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