Factors to induce the ripening of persimmon fruit and its role for decreasing of astringency during maturation.

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The ripening process of persimmon fruit do not show a clear pattern of climacteric fruit. CO_2 evolution is very low and trace amount of ethylene has been detected during ripening, so that the role of ethylene for ripening is still obscure in persimmon fruit. The objective of this study is to make clear whether or not ethylene is involved in ripening process and there are other factors except for ethylene to induce ripening in persimmon fruit. 1. When ethylene evolution of persimmon fruit was measured periodically, the relationship of ethylene evolution and ripening process was not clear. And also, when endogenous ethylene was applied to the fruit on the tree during growing season, treatments at growth stage III have been effective to promote ripening, while not being effective at growth stage II. These results indicate that ethylene might be a complementary factor for ripening in persimmon fruit. 2. ABA and gibberellin were closely associated with ripening process. ABA contents increased and activities of gibberellin-like substances decreased in relation to ripening process of fruit. Protein constituents of the fruit were also markedly changed at transition period of growth stage II to III. There is a special protein associated with ripening, which appeared at the initiation of ripening and increased during ripening process. 3. As the results of calyx lobe removal and temperature treatment to the fruit, fruit development and ripening process were greatly affected. Interesting aspect is that the inhibition of fruit development and ripening caused by calyx lobe removal was associated with sugar metabolism. Calyx-removed fruit accumulated much sucrose with decreasing glucose and fructose compared to control fruit. This result suggested the involvement of enzymes for sucrose hydrolysis in the fruit development and ripening. This hypothesis should be certified by further investigation.