EFFECT OF La~(3+) ON GROWTH AND ACTIVITIES OF ANTIOXIDANT ENZYMES IN RICE SEEDLINGS UNDER COPPER STRESS

The effects of La(NO3)3 on the growth,the activities of antioxidant enzymes(SOD and CAT),the level of malondialdehyde MDA)and the penetrability of cell membrane in shoots and roots of rice seedlings under copper stress were evaluated by the nutrient solution culture experiment.The results showed that for the seedlings,10 mg·l-1 La(NO3)3 could improve the activities of SOD significantly(p0.05),increase the activities of CAT,and decrease level of MDA during the initial stage(0—3d) under copper(CuSO4 concentrations of 100 mg·l-1 and 200 mg·l-1) stress.With the time of copper stress prolonged(3—9d),the activities of antioxidant enzymes declined gradually and the level of MDA increased gradually,suggesting that the protective effects of lanthanum were reduced.Lanthanum even could cooperate with copper at later stages(9th d),then copper injured rice seedlings more grievously.The synergy of La and Cu was more obvious under 200 mg·l-1 CuSO4 stress,thus the penetrability of cell membrane was increased significantly(p0.05) and the growth of rice seedlings was inhibited.It was indicated that proper lanthanum concentration could be selected to enhance the copper tolerance abilities of rice seedlings,but this relieving function of lanthanum was closely correlative with the concentration and time of copper stress.