Changes In Soluble Sugars And Organic Acid Of Grape Berries During Fruit Ripening And Delayed Harvest

Changes in soluble sugars and organic acids were studied during fruit ripening and delayed harvest in grape berries from 20 individuals of the cross progenies from two crosses—'Jingxiu'×'Alexander'and'Jingxiu'×'Xiangfei'—during two successive years. Sugar content and activities of enzymes on sucrose metabolization in grape berries were measured weekly after maturation for three weeks with two cultivars and two hybrids, which won't change externally during delayed harvest. At the same time, the respiratory rate of the berries was measured. The main results were show hereinafter.Soluble sugars of 8 individuals accumulated significantly during three-week delayed harvest period while no significant changes in soluble sugars were observed in the other 12 individuals. Glucose and fructose were the predominant sugars in grape berries. More fructose accumulates in sugar accumulation type than glucose. Organic acids change a little during delayed harvest and show no difference between two sugar types.Acid invertase (AI), neutral invertase (NI), sucrose synthase cleavage direction tended to increase during the delayed harvest period in'Jingxiu'and'97-2-23',which belonged to sugar accumulation type, while those of'Alexander'and'97-2-24', which were the sugar stable type, decreased significantly when fruit became overripe during the three weeks of delayed harvest. Moreover there was difference in the respiratory rate of berries between the two types. It is suggested...