Sugar imetabolism of the fruit and its involvement in fruit growth

本课题以柿子果实为研究对象，探讨了果实形成沉强的机理。作为模型材料的去除花萼裂片的平田仁。在柿子生长早期去除花萼裂片对果实生长有很大的抑制作用。去花萼后，赤霉素样蛋白活性和脱落酸含量均降低。此外，除去花萼对果实的糖组成有显著影响。在处理过的果实生长受到抑制的同时，果肉中蔗糖与己糖（葡萄糖和果糖）的比例显著增加。由于蔗糖是柿子中的易位糖，因此可能造成不合适的梯度，不利于果实进一步进口同化物。由于去除萼瓣后果实中糖的变化与生长抑制一致，因此研究了去除萼瓣后与糖代谢相关的酶。处理后果实糖代谢的改变可能是由于酸转化酶活性下降所致。在生长早期去花萼的果实中，酸转化酶活性表现出较高的抑制水平。在两个生长季节，研究了去除花萼对柿子果实CO_2交换率的影响。结果表明，去除花萼对CO_2交换速率和果实生长有显著影响。在果实生长早期去除花萼会显著抑制果实CO_2交换速率。由于CO_2交换速率的快速下降反映了果实呼吸速率的下降，这可能表明抑制了果实中从头合成的蛋白质，包括酸转化酶。我们认为，去花萼抑制果实生长的主要原因是果实呼吸能力的下降，而呼吸能力的下降会引起酶活性的抑制，从而影响果实生长的代谢。

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.