Abstract: In field test, the influence of malic acid, malonic acid and citric acid on physiological properties and chemical components of oriental\|tobacco was studied in Xinchang, Zhejiang Province in 2009. The results indicated that the three organic acids could obviously promote the growth and development of oriental-tobacco and increase the activities of invertase, sucrose synthase, sucrose phosphate synthase and glutamine synthetase of tobacco leaves in early growing stages. In later growing stage, organic acids could obviously promote the degradation of chlorophyll and promote the maturation of tobacco leaves in time. Meanwhile, the total sugar and potassium content increased and total nitrogen, nicotine and chloridion contents decreased in different degrees in the treatment of organic acids. Thereby, the chemical components in tobacco leaves were coordinated and balanced and the quality of tobacco leaves were improved. Among these three organic acids, the effects of malic acid and malonic acid were better than citric acid．

Key words: oriental-tobacco, organic acid, nicotine