Abstract: Jumeigui’grape（Vitis vinifera L. × V. labrusca L.）was subjected to root restriction to study the metabolic mechanism of soluble sugar accumulation in grape berries during the berry development from veraison to maturation. The results showed that the main sugars accumulated in ‘Jumeigui’grape were glucose and fructose. From the beginning of veraison，contents of glucose and fructose in berries increased continuously，and meanwhile acid invertase（AI）activity increased gradually with berry development. What’ more，AI activity was significantly correlated with the contents of glucose and fructose which are the most important soluble sugars in the grape berry. The activity of neutral invertase（NI）and sucrose synthase（SS）activity in the sucrose cleavage direction increased 3 weeks after veraison and lower than that of AI. The activity of enzymes for sucrose synthesis including sucrose synthase（SS）in the sucrose synthetic direction and sucrose phosphate synthase（SPS）increased slightly just at the early veraison and then kept constant，and was lower than that of SS in the sucrose cleavage direction，AI and NI related to sucrose cleavage. The root restriction could increase the content of soluble sugars in grape berries and enhance AI activity during the period of sugar accumulation and NI activity at harvest. Therefore，we speculate that AI is the most important regulator for sugar accumulation and also the key enzyme accounting for increased sugar content by root restriction cultivation.

Key words: grape, root restriction, soluble sugar, acid invertase