Regulation Of Exogenous Nitric Oxide To Medicago Sativa Physiological Characteristics And Resistance Genes Expression Under Environmental Stress

Mainly by using pot culture methodology and combined with the methodology currentlyapplied in the research fields of Plant Physiology, Bio-chemistry and Molecular Biology, startedwith the systematic analysis of plant biology and physiological responses on salt and drought stress,studies on regulation of different concentrations（0.1and1.0mmol/L） of exogenous nitric oxide toMedicago sativa seed germination, physiological characteristics, antioxide ability and seedlingsresistance genes were carried out in present thesis. The results varied as following:1.The Medicago sativa seeds were soaked in different concentrations （0.1and1.0mmol/L） ofsodium nitroprusside（SNP） for48h, exogenous nitric oxide treatments could dramatically promotedgermination rate, germination energy, germination index and vigor index of Medicago sativa seedsunder NaCl and drought stress, the protective ability of concentrations of0.1mmol/L was significantly betterthan the concentrations of1.0mmol/L.2.The influence of exogenous nitric oxide donor, SNP, at concentrations of0.1and1.0mmol/Lon seedling leaves oxidative damage in Medicago sativa under NaCl stress and drought stress werestudied through8days of treatments, the results indicated the activities of antioxidant enzymeswere increased, such as superoxide dismutase（SOD）, peroxidase（POD） and catalase（CAT）,accelerate the the clearance rate of reactive oxygen species, alleviated the oxidative damage causedby salt stress and drought stress on the seedling leaves, and then to improve salt and droughtresistance in a Medicago sativa, the best effect was observed in the treatment of0.1mmol/L SNP.3.During the NaCl stress and drought stress, the content of proline and soluble sugar wereincreased significantly by exogenous nitric oxide, reduced the osmotic potential of cells, maintainedthe turgor pressure of cell, and then to improve the salt tolerance and drought resistance of seedlings,the most significant effect of processing to0.1mmol/L SNP.4.The O₂-production speed, the content of malondialdehyde（MDA）, H₂O₂and chlorophyllwere down-regulated by the exogenous nitric oxide in Medicago sativa seedling leaves, whichwould reliefed the oxide damage, thereby improving salt and drought resistance, of which the mostsignificant effect of processing was0.1mmol/L SNP.5.The resistance gene P5CS and LEA3expression were assayed by semi-quantitative RT-PCRat mRNA level in Medicago sativa plants treated with, the expression of the gene P5CS showed the wavy growth induced by0.1mmol/L SNP under NaCl stress, and peaked at24h and48h,synthesized a large number of proline, thereby increasing the salt tolerance of Medicago sativa;There has the maximum expression of LEA3under drought stress at48h, synthesized a largenumber of LEA proteins, and to improve the drought resistance of Medicago sativa.