Abstract: The content of sucrose , glucose , fructose and the activities of sucrose-metabolizing enzymes (acid invertase , neutral invertase , sucrose synthase and sucrose phosphate synthase) in the fruits of Citrus unshiu Marc. cv. Miyagawa wase were measured. It was observed that compositive
action of sucrose-metabolizing enzymes (net activity of sucrose-metabolizing enzymes) was one of the important factors affecting sugar accumulation in fruit . The transition of sugar accumulation and net activity of sucrose-metabolizing enzymes was the period from the end of fruit enlargement to the onset of fruit coloring in fruits. Before the stage of fruit coloring , the net activity of sucrose-metabolizing enzymes was below zero , sucrose accumulated slowly in fruit . During stage of fruit coloring , the net activity of sucrose2metabolizing enzymes was positive , and sucrose accumulated rapidly in fruit . During the stage of fruit full ripe the net activity of sucrose2metabolizing enzymes was negative in peel tissue , and accumulation of hexoses was higher in comparison with edible tissue.

Key words: Citrus, Citrus unshiu Marc. cv. Miyagawa wase, Accumulation of sugars, In2vertase, Sucrose synthase, Sucrose phosphate synthase