关键词: 脐橙, 果实, 有机酸, 柠檬酸合成酶, 磷酸烯醇式丙酮酸羧化酶

Abstract: The activity variance of enzymes related to organic acid metabolism and the relationship between enzymes and organic acid accumulation in pulp during development of Robertson Navle orange fruit were studied. The results showed:①From June to August, the activity of citrate synthetase(CS) increased rapidly and reached the maximum in middle of August, then decreased rapidly. In middle of October, CS activity returned to rise and decreased again. ②From June to August, the activity of phosphoenolpyuvate carboxylase(PEPC) increased rapidly, in middle of August reached the maximum. After the fruit inflation stage, PEPC activity decreased rapidly and it didn't change on the whole in telophase and the mature stage. ③The variance tendency of activities of CS and PEPC were consistent with that of organic acid content. There was a significant positive correlation between the activity of CS or PEPC and organic acid, their correlation coefficients(r) were 0.9160 and 0.8779 respectively. These results proved that CO₂ fixation was a main pathway of organic acid synthesis in Navel orange fruit. They proved also that CS and PEPC were the key enzymes of organic acid synthesis. Efficiently inhibition of CS and PEPC activity could reduce the organic acid content of orange fruit.

Key words: NAVEL ORANGE(CITRUS SINESIS OSBECK), FRUIT, ORGANIC ACID, CITRATE SYNTHETASE(CS), PHOSPHOENOLPYUVATE CARBOXYLASE(PEPC)