中文摘要：

以储良龙眼为试材,在果实发育的中期和后期分别对结果母枝进行环割＋去叶处理,中断果穗碳素营养的供应,研究饥饿胁迫下果实脱落、果实中糖含量及相关酶类的变化。结果表明,龙眼结果母枝环割＋去叶处理所产生的饥饿胁迫在处理后2 d内引发果实大量脱落,果实中可溶性糖明显下降,但并未耗尽,因此果实糖含量可能存在一个阈值,低于该阈值,便触发果实的脱落;饥饿胁迫同时还引起了果实糖分组成的变化,蔗糖和葡萄糖相对降幅高于果糖;饥饿胁迫下,蔗糖分解方向的酶活性一度增强,但随着蔗糖含量的降低,蔗糖分解代谢酶活性转而减弱;而饥饿胁迫对SPS催化的蔗糖合成代谢影响不明显。

英文摘要：

Effects of carbohydrate starvation stress created by girdling plus defoliation made on bearing shoots on sugar contents and composition and the activities of sugar metabolism-related enzymes in fruit were investigated in longan（Dimocarpus Longana Lour.） cv.Chuliang.Girdling plus defoliation treatment was carried out on bearing shoots at two fruit developmental stages,ie.the middle stage（May 22,2009） and the late stage（June 22,2009） and changes in fruit drop rate,sugar contents and related enzymes were observed or analyzed.The results showed that girdling plus defoliation on bearing shoots interrupted the supply of carbon nutrition to fruit and caused severe fruit abscission.The treatment also induced a significant decline in soluble sugar concentrations in fruit at both stages,but fruit sugars were not fully depleted.It was suggested that there might be a threshold sugar level in fruit,below which fruit abscission occurs.Starvation stress also led to the changes in sugar composition.The relative declines of sucrose and glucose were higher than that of fructose.Sucrose degradation enzymes（invertase and sucrose synthase） increased within 2 d after starvation stress,but with the decreasing of sucrose in fruit,activities of these enzymes decreased.The activity of sucrose phosphate synthase（SPS） that catalyzes sucrose synthesis was not significantly affected by starvation.