Effect of Rare Earth on Membrane Lipid Peroxidation of Soybean Seedlings Under Supplemental UV-B Irradiation:IIts Influence on CAT and POD Activities

Effects of lanthanum(La3+)on membrane lipid peroxidation and antioxidant enzymes such as CAT and POD of soybean seedlings under elevated ultraviolet-B radiation(UV-B:280～320 nm)at 15(?)W·cm-2 and 45(?)W·cm-2 level were investigated with hydroponics under laboratory conditions.The result showed that plasmolemma permeability and MDA content of soybean seedlings gradually increased under supplemental ultraviolet-B stress and then decreased after the removal of ultraviolet-B radiation.The dynamic of CAT activity was similar to that of plasmolemma permeability and MDA content.The activity of POD firstly increased,maintained a high level and fell down steeply when soybean seedlings were exposed to low dosage of UV-B radiation.However,POD activity of soybean seedlings under high level of UV-B radiation stresse rose all the time and declined slightly on the 7th day.With the mediation of La,during the period of light recovery the range of variation of plasmolemma permeability and MDA content declined,with the activities of CAT and POD higher than that of UV-B treatments,suggesting that the regulative effect of La on antioxidant enzymes such as CAT and POD alleviated the injury of UV-B radiation to their function,strengthened their capacities to scavenge reactive oxygen species(ROS),improved the metabolism of ROS,diminished the concentration of MDA,maintained normal permeability of membrane,and that its protective effect against low UV-B radiation was superior to that of high UV-B radiation.So,the defensive effect of La on soybean seedlings under UV-B stress was carried out on the layer of defense system.