| Drought has a great infection on plant growth and development, even normal growth, it is an important abiotic stress in the nature. NO is a kind of biologic and active molecule.The research of NO on plant has acquired a great of success, but comparing to the research on animal, it is also has a big difference. The origin of NO in plant's body and its functional modes are also not clear. The relationship between the donor's concentration of NO and the physiological response of plant which under osmotic stress need to research and validate.For researching the accomodation effects and mechanism of NO to the drought-resisting plants. In this research, the material is the desert plant Haloxylon ammodendron, that after the treatment at different concentration of -0.2,-0.3,-0.5,-0.8,-1.0和-1.5MPa of PEG, add to SNP at the concentration of 0.1mmol·L-1, 0.3mmol·L-1 and 0.5mmol·L-1, and then give darkness treatments. we use the donor of NO then give the plant darkness treatment, to research the infection of extrinsic NO on Haloxylon ammodendron seed germination and seeding growth which under Osmotic stress. Primarily discuss that extrinsic NO on improving hardiness of Haloxylon ammodendron which under osmotic stress and its mechanism. TO conclue the results as following:1) Along with the increase osmotic stress degree, the Haloxylon ammodendron seed germination rate gradually readuce. When the stress degree was -1.5MPa, the seed germination was compeletely restrained. After the treatment of SNP, it can be catabatic on the effects ,that the osmotic stress to the seed germination. When the osmotic stress was -1.0MPa, to contrast with the CK, the seed germination has obvious difference.2) Under the PEG stress, the treatment SNP can improve the growth of seeding's root and stem's length, increase the dry weight of the root, stem and leaves; Thereinto when the 0.3mmol·L-1 SNP effection was the most obvious. When the condition of -0.5MPa, seeding root and stem length has improve 34% and 21% respective.3) The treatment of extrinsic NO improved the Haloxylon ammodendron seeding leaf Chlorophyll content, the degree of stress is deeper the influence is clearer; thereinto the SNP treatment at the concentration of 0.3mmol.L-1 has the most evidently stimulative effects on the Chlorophyll content.4) The treatment of extrinsic NO reduce the electrolyte leakage and the accumulation of MDA of Haloxylon ammodendron seedings which under Osmotic stress. Thereinto, the SNP treatment at the concentration of 0.3mmol.L-1 has the most evidently effects on protecting the cell velum.5) On the early stage of Osmotic stress treatment, the activity of SOD and POD in Haloxylon ammodendron leaf improved evidently, the Superoxide Anion Radical Production rate declined, but on the late stage of the osmotic stress treatment, especially at the fourth day of drought treatment with PEG at the concentration of -1.0和-1.5MPa, the activity of SOD and POD declined quickly, the Superoxide Anion Radical Production rate rised evidently; the adjustive functions of plant became exceptional. After the SNP treatment, it could induced the activity of SOD and POD, so that it could reduce the damage of oxidation which osmotic stress caused.6) The treatment of extrinsic NO improved soluble protein content and Leaf relative water content under the osmotic stress. The degree of stress is deeper the releasing effects are clearer. Thereinto, after the SNP treatment at the concentration of 0.3mmol·L-1, the increase of soluble protein content is clear, the concentration of 0.1mmol·L-1 took second place, and the concentration of 0.5mmol·L-1 was the last.
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