Influence of Different Maturity on Characteristic of Lipid Peroxidation in Flue-cured Tobacco Leaves

The effects of different maturity on the activity of superoxide dismutase(SOD),peroxidase(POD) and polyphenoloxidase(PPO),and malondialdehyde(MDA) content in the leaves of flue-cured tobacco(Nicotiana tabacum L.) in Nanyang city of Henan province were studied.The results indicated that:(1) When the maturity of tobacco leaves increased,the activities of SOD,POD and PPO all rose firstly,and then declined in general,while MDA content increased all the time on the whole.However,the activity of different enzymes peaked at different mature stage,the activity of PPO in the middle and upper leaves appeared peak at completely ripe stage,while that in the lower leaves appeared peak at sub-mature stage;the activity of POD and SOD in the middle and upper leaves appeared peak at unripe stage and sub-mature stage respectively.(2) From immature stage to mature stage,the activities of PPO,SOD and POD in middle and upper leaves were all greater than those in lower leaves;from sub-mature stage to mature stage,the activities of SOD,POD and PPO all declined sharply.So it was comprehensively considered that the lower leaves of flue-cured tobacco should be harvested at sub-mature ～ mature stage,and middle and upper leaves should be harvested at ripe ～ overmature stage.