Dynamic Responses of Antioxidative Defense System of Lespedeza davuricato Drought and Enhanced UV-B Radiation

The effects of drought and enhanced UV-B radiation on the antioxidant defense system and membrane lipid peroxidation in Lespedeza davurica were investigated.Compared with the single-stress of drought,the co-stresses of drought and enhanced UV-B radiation decreased the activities of superoxide dismutase(SOD) and catalase(CAT),and increased the activities of ascorbate peroxidase(APX) and peroxidase(POD).SOD activity under the co-stresses of drought and low UV-B radiation intensity was significantly lower than that under the single-stress of drought.With the increase of UV-B radiation intensity under co-stresses,POD activity decreased while activities of APX and CAT increased.Compared with the single-stress of drought,the co-stresses of drought and different UV-B radiation intensities increased ascorbic acid(AsA) content and decreased the contents of chlorophyll(Chl) and carotenoid(Car).With the increase of UV-B intensity under co-stresses,AsA content initially increased then decreased while the contents of Chl and Car decreased.During the first six days of the co-stresses of drought and low UV-B radiation intensity,anthocyanin content significantly increased compared with control.During the early stage of the co-stresses of drought and enhanced UV-B radiation,the contents of malonaldehyde(MDA) and O-2 decreased compared with the single-stress of drought.Comprehensive evaluation according to subordinate function indicated that both single-stress of drought and co-stresses could increase the antioxidant ability of Lespedeza davurica,and the co-stresses of drought and low UV-B intensity improved antioxidant ability more.