Involvement of respiration rise at growth stage III in fruit enlargement and maturation of persimmon [Diospyros kaki] fruit

Fruit growth of persimmon follows a double sigmoidal curve. With the onset of growth stage III, fruit start their final swell and enter the maturation phase. We investigated the seasonal changes in respiration rates of persimmon fruit in the field condition, and discovered that fruit respiration showed a rapid increase with the onset of growth stage III. This result indicates a possibility that this respiration rise at growth stage III may have a close relationship to final swell and maturation. Since many stomata are distributed on the calyx lobes, but not on the fruit surface, the calyx lobes are generally agreed to to be "the gas exchanging site" of the fruit. Therefore, by removing the calyx lobes and sealing the scars with Vaseline, we are able to markedly inhibit the respiration rise at growth stage III. As a result, final fruit swell and accumulation of l3C-photoassimilate were visibly reduced. The inhibition of fruit respiration seemed to reduce the sink strength of the fruit, which in turn suppressed fruit growth. It was concluded that the high respiration during growth stage III in persimmon fruit is important for maintaining sink strength for the final swell of fruit. Gibberellic acid treatment at growth stage II or III delayed fruit coloring and softening. On the other hand, abscisic acid treatment at growth stage II promoted fruit coloring. In connection with these effects, the respiration rise was retarded by gibberellic acid treatment and advanced by abscisic acid treatment. These results suggest that the respiration rise at growth stage III may have a close relationship to the maturation of persimmon fruit. During the period when the fruit respiration rise at growth stage III was observed, ethylene production rates showed no changes. This suggests that ethylene has no relation to the respiration rise and that the respiration rise is different from that in climateric fruit