脐橙果实发育中有机酸合成代谢酶活性变化的研究

以红桔砧 10年生罗伯逊脐橙为试材 ,研究了脐橙果实发育过程中有机酸代谢有关酶的活性变化及其与有机酸积累的关系。结果表明 :①从 6～ 8月柠檬酸合成酶 (CS)活性迅速增加 ,8月中旬达到高峰 ,随后迅速下降 ,在 10月中旬其活性出现回升后又再次下降 ;② 6～ 8月磷酸烯醇式丙酮酸羧化酶 (PEPC)活性迅速上升 ,8月中旬达到高峰 ,进入果实膨大期后 ,PEPC活性迅速下降 ,在果实膨大末期和成熟期其活性基本不变 ;③在整个果实发育过程中 ,CS、PEPC活性的变化趋势与有机酸含量的变化趋势一致 ,并呈极显著正相关 ,相关系数 (r)分别为 0 916 0和0 8779。这不仅证明脐橙果实中存在通过CO2 固定合成有机酸的途径 ,还说明CS、PEPC是有机酸合成的关键酶 ,有效地抑制CS的活性能降低果实中有机酸的生成量

Study on the Change of Organic Acid Synthetase Activity During Fruit Development of Navel Orange (Citrus Sinesis Osbeck)

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.