Relationship between accumulation of organic acid and organic acid-metabolizing enzymes during apricot fruit development.

The contents of organic acids and the activities of organic acid-metabolizing enzymes,including citrate synthase (CS), phosphoenolpyruvate carboxylase(PEPC), Aconitase(ACO), and malate dehydrogenase(MDH) were measured during the fruit development of Xinshiji apricot,and their correlations were analyzed. The results showed that there were malic acid and citric acid in fresh apricot fruit,and malic acid was the dominant (95%) in ripe fruit. Concentration of organic acid gradually increased during fruit development and peaked 51 days after anthesis and then declined slightly. Correlation analysis showed that a positive correlation was observed between the content of malic acid and the activity of MDH,while there was a significant negative correlation between the content of malic acid and the activity of CS and ACO. The content of citric acid was positively relevant with CS,and significantly negatively relevant with MDH,with the correlation coefficient being 0.8675*. It is suggested that CS,MDH and ACO were the main enzymes in organic acid accumulation of apricot fruit.,but not PEPC.