[Objectives]This study was conducted to investigate the effects of UV-B radiation on the activity of main antioxidants in flue-cured tobacco.[Methods]The flue-cured tobacco variety Yunyan 87 was used as the test material for pot planting.Xuanwei County(1997 m)in Qujing Tobacco District,Yunnan was selected as the test point.Three levels of UV-B radiation was set to investigate the activity of PPO,SOD,POD and CAT and the contents of flavonoids and malondialdehyde during the development of the middle leaves of flue-cured tobacco in the same planting area by reducing the natural conditions by 75.04%(A1),70.01%(A2)and 30.02%(A3),respectively.[Results]Reducing UV-B radiation significantly increased the activity of tobacco SOD,POD and CAT,which showed that flue-cured tobacco in the low-latitude plateau area of Yunnan has adapted to the higher local UV-B radiation,and the flue-cured tobacco has formed a unique antioxidant enzyme system.The weakening of UV-B radiation treatment might partially change the antioxidant enzyme system of flue-cured tobacco,but there were no significant differences in the activity of antioxidant enzymes between different degrees of weakening UV-B radiation.The change trends of flavonoids and malondialdehyde in leaves at two different leaf positions were similar.The malondialdehyde content of treatment A1 was significantly higher than those of the CK,A2 and A3,and 70.01%-75.04% of UV-B radiation intensity might be the lower limit of Yunyan 87''s adaptability to UV-B radiation.With the decrease of UV-B radiation,the sensitivity of flue-cured tobacco gradually decreased.[Conclusions]This study made a preliminary exploration for explaining the correlation of UV-B radiation and Yunnan flue-cured tobacco.
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