Effect of Osmotic Stress and Calcium Treatment on Membrane lipid Peroxidation and Protective Enzyme in Chinese Fir Seedling

The effects of osmotic stress induced by PEG (1.5 MPa,-2.5 MPa) on hydrogen peroxide (H2O2) content,membrane lipid peroxidation and activities of superoxide dismutase (SOD),peroxidase (POD) and catalase (CAT) in levies of Chinese fir (Cunninghamia lanceolata) were studied. The results showed that malondialdehyde (MDA) content increased and activities of SOD and POD decreased with osmotic stress time (24,48,72 h) and osmotic stress strength (-1.5 MPa,-2.5 MPa),but H2O2 content increased for 48 h then fell and CAT activity decreased for 24 h then raised under osmotic stress (-2.5 MPa). When seedlings were sprayed with CaCl2 (7 mmol·L-1) solution,raising rates of contents of H2O2 and MDA,and decreasing rates of activities of SOD and POD obviously slowed down,respectively. CAT activity quickly raised after it decreasing under osmotic stress,when seedlings were sprayed with CaCl2 solution.