Sugar imetabolism of the fruit and its involvement in fruit growth

点击翻译按钮获取中文摘要

This project was conducted to elucidate the mechanism of the formation of sink strength by the fruit, using persimmon fruits of cv.Hiratanenashi with calyx lobes removed as a model material.1. The fruit growth of persimmon was greatly inhibited when calyx lobes were removed at early stages of growth. Both gibberellin-like activity and abscisic acid content were decreased after the calyx lobe removal. Moreover, sugar composition of the fruit was remarkably affected by the calyx lobe removal. Coincident with growth inhibition of the treated fruits, the ratio of surcrose to hexoses(glucose and friutose) increased significantly in the flesh It may create an unsuitable gradient for further import of the assimilates by the fruit, since sucrose is the translocated sugar in persimmon.2. As changes in constitutibe sugar were found by calyx lobe removal coincident with fruit growth inhibition, the enzyme related to sugar metabolism was investigated after calyx lobe removal. The modification in sugar metabolism of the treated fruit may be due to decline of acid invertase activity. High level of inhibition of acid invertase acitvity was exhibition in fruits with the calyx lobes removed at early growth stages.3. The effects of calyx lobes removal on the CO_2 exchange rate of attached persimmon fruit was investigated during two growing season. It revealed that CO_2 exchange rate was remarkably influenced as well as fruit growth by calyx lobe removal. The calyx lobe removal at early stages of fruit growth greatly inhibited fruit CO_2 exchange rate. Since rapid decrease in CO_2 exchange rate reflects the decline of respiration rate of the fruit, this may indicate the inhibition of de novo protein synthesis in the fruit, including acid invertase.We now conclude that the main cause of fruit inhibition by calyx lobe removal is the decline of fruit respiration, and that this decline will induce the inhibition of enzyme activity which affects the metabolism for the growth of the fruit.