Effects of exogenous nitric oxide on seed germination and seedling oxidative damage in Medicago sativa under NaCl stress

1)Medicago sativa seeds were soaked in two concentrations(0.1and 1.0mmol/L)of sodium nitroprusside(SNP)for 48h.Samples of 50seeds taken on 10consecutive days were cultured in dishes under conditions of constant light and temperature at(25±1)℃.NaCl solution(6mL 0.15%)was added to investigate the effects of exogenous nitric oxide on seed germination under NaCl stress.2)The influence of the exogenous nitric oxide donor(SNP)at concentrations of 0.1and 1.0mmol/L on M.sativaseedling leaf oxidative damage under 0.15% NaCl stress were studied for 8days of treatment.The treatments were,T1:CK(distilled water);T2:0.15% NaCl;T3:0.1mmol/L SNP+0.15% NaCl;T4:1.0mmol/L SNP+0.15% NaCl.The results indicated that germination rate(P0.01),germination energy,germination index(P0.05)and vigor index(P0.05)of M.sativaseeds were dramatically promoted by SNP treatments during germination under 0.15% NaCl stress.The activities of antioxidant enzymes such as superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT),were increased,which is consistent with the up-regulation of proline and soluble sugars,and with the down-regulation of O2-production,speed and content of malondialdehyde(MDA),H2 O2 and chlorophyll in M.sativaseedling leaves compared with those under salt stress.Meanwhile,the protective ability of concentrations of 0.1mmol/L was significantly better than those of 1.0mmol/L.