Effects of Attenuated UV-B Radiation on Dynamic Changes of Photosynthetic Pigment Contents in Flue-cured Tobacco under Natural Conditions

In the outside field condition,Yunnan flue-cured tobacco variety-K326 was potted under different types of transparent films which were used to reduce solar UV-B radiation,and the UV-B penetration rate was 100%(CK),75%(T1),50%(T2),35%(T3),respectively.The dynamic changes of flue-cured tobacco photosynthetic pigment contents under different radiant intensity of UV-B radiation treatments were studied.The results showed that three kinds of flue-cured tobacco photosynthetic pigment contents had different sensibility to UV-B radiation.Carotenoid was more sensitive to UV-B radiation than other photosynthetic pigments.In the earlier stage of mature,the sensitivity of carotenoid had preferable coherence to UV-B radiation,while the contents of chlorophyll a and chlorophyll b had a counter-relation of change to it,due to the accumulative effect of UV-B radiation,there was no significant change of photosynthetic pigments contents in the late stage of mature.During the earlier period of budding and maturation-baking,the ratio of chlorophyll a and chlorophyll b had a significant counter-relationship to responding UV-B radiation,by contrast,there was no significant difference in the late stage.The downtrend of photosynthetic pigment contents was related to the accumulative effect of solar UV-B radiation.