Effect Of Drought Stress On Physiological Characteristics Of Agropyron Mongolicum Keng Seedlings And Seed Germination

Drought stress has great impact on plant growth and development. In this thesis, The effect of droght stress on seedling growth and seed germination of Agropyron mongolicum Keng was studied using polyethylene glycol (PEG-6000) to mimic drought stress. The main results were presented as follows:1. The growth of A.mngolicum seedlings was inhibited when the seedlings were exposed to PEG-induced drought stress, and treatment with PEG induced the accumulation of hydrogen peroxide (H2O2), superoxide anion radical (O2·﹣) and malondialdehyde (MDA). The activities of antioxidative enzymes of A. mongolicum seedling were significantly reduced by PEG treatment which including CAT, POD and SOD. The RT-PCR analysis indicated that relative expression of APX4, CAT1, Fe-SOD3 and Mn-SOD genes was down-regulated by the PEG treatment. These results indicate that the activities of antioxidative enzymes were reduced due to down regulation of gene expression, leading to oxidative stress under conditions of drought stress.2. Seed germination of A. mongolicum was markedly reduced by treatments with both PEG and H2O2 , and the inhibitory effect by PEG and H2O2 were additive. The contents of hydrogen peroxide (H2O2) and superoxide anion radical (O2·﹣) in A. mongolicum seeds were not affected by PEG treatment, while the activity of CAT was inhibited by PEG treatment. Exogenous CAT, SA and Na2SiO3 significantly alleviated the PEG-induced inhibition of seed germiantion. These results indicate that the ameoliative effect of SA and Na2SiO3 on PEG-induced inhibition of seed germination may be related to reduced production of H2O2.