The Response Of Artemisia Sphaerocephala To Osmotic Stress And The Change Of Membrane Lipids Composition During The Process

Drought is one of the major environmental factors of the impact plants survival, growth and development. Researching the drought resilience mechanisms and suitability of desert plants to drought has great significance for the protection and use of desert plants and recovery and reconstruction of the vegetation in the desert region. In this thesis, treated with0、5%、10%、15%、20%、25%、30%of polyethylene glycol (PEG-6000), the effects of osmotic stress on the physiological and biochemical characteristics of Artemisia sphaerocephala seeding were studied. The main results were shown as follows:(1)With increased osmotic stress, the leaf relative water content declined gradually, while the relative conductivity and malondialdehyde content increased significantly. Below20%PEG treatments, Artemisia sphaerocephala could resist osmotic stress by closing stoma; with further increased osmotic stress, photosynthetic rate decreased by non-stomatal limitation.(2) Under osmotic stress, the compositions of fatty acids showed no change in leaves, but the content of fatty acid compositions changed significantly. With the increased osmotic stress, saturated fatty acid content increased, polyunsaturated fatty acids content reduced. Under mild osmotic stress, leaves lipid tended to be saturated, which reduced the chance of peroxidation of unsaturated fatty acid and prevented damage of cell membranes; under severe osmotic stress, lipid saturation led to membrane function impairment.(3) Linoleic acid contents increased significantly with the increasing osmotic stress, which played important roles in maintaining certain membrane lipid unsaturation in Artemisia sphaerocephala leaves. The mild and moderate osmotic stress induced expression of AsFAD2gene; however, its expression was inhibited by severe stress.(4) Under osmotic stress, superoxide dismutase activity, vitamin E, proline and soluble sugar showed the increasing trend, peroxidase and catalase activity increased firstly and then decreased. Under mild osmotic stress, the protective materials synergy together to maintain the stability of plant cell membrane; under severe osmotic stress, proline content increased, antioxidant enzyme system imbalanced.They can could not reversal the fact that plant had been damaged by severe osmotic stress.