Physiological Mechanism on the Difference of Sugar Accumulation in Four Citrus Varieties

The concentration of sucrose, glucose, fructose, titratable acid, ABA and the activity of acid invertase (AI) were measured in juice sacs of Bendizao mandarin (Citrus succosa Hort), Ponkan (Citrus reticulata Blanco), Miyagawa wase (Citrus unshiu Marc) and Meyer lemon (Citrus meyeri Y). The acid hydrolysis of sucrose in vitro was also studied. The results showed that the sugar content, the ratio of different sugars, titratable acidity, ABA content and the activity of AI were obviously different in four citrus varieties. The sugar content in juice sacs of citrus fruit was related to that of ABA at the late stage of fruit development. The result suggested that ABA played an important role in sugar accumulation in juice sacs of citrus fruit. Bendizao mandarin and Miyagawa wase mainly accumulated sucrose in juice sacs of citrus fruit. Meyer lemon accumulated hexose, and Ponkan citrus was the sucrose-hexose accumulating type variety. In Meyer lemon with high acid degree, the composition of sugar in juice sacs was determined by acid-hydrolysis of sucrose. In Bendizao mandarin, Ponkan citrus and Miyagawa wase with low acid degree, the composition of sugars at the late stage of fruit development was obviously affected by the AI activity.

柑橘品种间糖积累差异的生理基础

测定了本地早、柑、香柠檬和宫川汁囊中蔗糖、葡萄糖、果糖、可滴定酸以及ABA的含量 ,分析了酸性转化酶 (AI)的活性 ,并模拟汁囊条件对蔗糖的酸水解进行了研究。结果表明 ,不同品种的糖含量和构成比例、酸含量、ABA含量以及AI活性都存在明显差异。在果实发育后期 ,汁囊中的ABA与糖含量都明显升高 ,呈极显著相关 ,表明ABA对糖的积累具有重要影响。本地早和宫川以积累蔗糖为主 ,香柠檬以积累己糖为主 ,柑介于二者之间。在酸度较高的香柠檬中 ,蔗糖的酸水解是影响汁囊中糖分构成的主要因素。在酸度较低的本地早、宫川和柑中 ,果实发育后期汁囊中的AI活性对糖分构成具有重要影响。