Effect of Soil Drught Stress on Membrane Lipid Peroxidation and Activity of Cell Defense Enzymes in Leaves of Epimedium Pubescens Maxim

In our study,Epimedium pubescens Maxim.was subjected to different soil drought stress by using pot culture experiments simulating four kinds of soil water: no drought stress(T1),mild drought stress(T2),moderate drought stress(T3) and severe drought stress(T4).Relative water content(RWC),malondialdehyde(MDA) content,cell membrane permeability(RC),as well as activities of superoxide dismutase(SOD),catalase(CAT) and peroxidase(POD) in leaves of E.pubescens were tested.We find that RWC decreased along with aggravation of soil drought stress and maintained above 70% under all kinds of stress.Mild drought stress significantly increased activities of SOD,CAT and POD,but increased little in MDA content and RC.Moderate drought stress significantly promoted activities of SOD,CAT and POD,as well as MDA content and RC.Under severe drought stress,RC continuously increased significantly,MDA content,POD activity increased little,SOD and CAT activities decreased significantly.Our results indicated that E.pubescens may keep water under soil drought stress.Plants inhibit membrane lipid peroxidation and maintain the stability of membrane system by increasing activities of cell defense enzymes,but this effct is effectual under mild soil drought stress.However,this protection would be weakened by aggravation of soil drought stress,membrane lipid peroxidation intensfy and stability of membrane system decrease under moderate drought stress.At last,SOD and CAT activities decrease under severe drought stress,and membrane system would suffer more serious damage.