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The application of gibberellin [GA31 to persimmon fruits as an orchard spray, at least 2 weeks prior to harvest, has been shown to delay ripening of the fruit on the tree and its rate of softening after harvest. This effect persisted during and after cold storage. The delay in softening has been attributed to the effect of the phytohormone on cell wall metabolism. To examine this hypothesis, cell walls of GAs-treated fruit were compared to those of non-treated fruit. Comparison between fruit was from harvest till the termination of post-storage softening. The study included TEM examinations, assay of certain hydrolase activities and determination of compositional changes occurring in the various cell-wall carbohydrate polymers. Our findings indicate that GA3 either delays or inhibits all of the cell wall changes that were found to accompany fruit softening, including dissolution of the middle lamella, separation of the plasmalemma from the cell-wall, mitigation of the structural coherence and density of the primary cell wall, increased solubilization of pectic polymers, loss of neutral sugars, predominantly arabinose and galactose, and increased activities of exo-polygalacturonase [PG] and endo-1,4-p-glucanase [EGase]. The principal discernible compositional difference between GAs-treated fruit and control fruit at harvest was a higher total carbohydrate content in the cell wall material extracted from GAs-treated fruit, which was due chiefly to an increased amount of cellulose.

Astringency was removed from 'Triumph' persimmons by immersion in water at 40°C for 5 hr or 6O"C, for 1 hr. Similar treatments at 20" and 8O"C, had no effect on astringency reduction. Subsequent application of 80% CO2 for 48 hr was effective for 20"C-treated fruit but not for 80YXreated fruit, which became nonastringent only after exposure to acetaldehyde. Extending the 60°C treatment beyond 2 hr resulted in recurrence of astringency, which was not reduced by subsequent COz treatment. Astringency also recurred in CO+eated nonastringent tit, when exposed to high temperatures. The disappearance and recurrence of astringency correlated with amount of methanolsoluble tannins.