Physiological and Biochemical Responses of Arachis hypogaea Seedlings to Enhanced UV-B

A field experiment was conducted to explore the physiological and biochemical mechanisms of the responses of the seedlings of peanut(Arachis hypogaea L.)cv.Xiaojingsheng to enhanced UV-B radiation(54μW/cm2).In the treatment of supplementary ultraviolet-B(UV-B),the contents of superoxide anion(O·-2),flavonoids and soluble proteins,the activities of catalase(CAT)and peroxidase(POD)and the relative electrical conductivity in the peanut leaves were increased significantly,the activity of superoxide dismutase(SOD)increased at first and then decreased;nevertheless,the contents of hydrogen peroxide(H2O2),malondialdehyde(MDA),ascorbic acid(AsA)and glutathione(GSH)and the activities of ascorbate peroxidase(APX)showed no significant changes in the leaves.These results indicated that elevated UV-B could significantly increase the content of reactive oxygen species(ROS)in peanut leaves,O·-2was the principal factor for oxidative stress,and peanut seedlings resisted the stress of ROS mainly through increasing the content flavonoids and the activities of SOD,CAT and POD,and that the AsAGSH circulatory system had no obvious effect on clearing ROS.