Effect Of Exogenous Nitric Oxide And Hydrogen Peroxide To Woad Seedling Growth And Oxidative Stress Reaction Under Salt Stress

Mainly by using pot culture methodology and started with the systematic analysis of plant biology and physiological responses on salt stress, studies on regulation of different concentrations of exogenous nitric oxide and hydrogen peroxide to woad seedlings resistance and growth and development were carried out in present thesis, including its possible mechanisms of plant salt resistance under salt stress in seedlings. The major results are presented as follows:1. Under 100 mmol/L NaCl stress condition, the different concentrations at 0.01,0.05, 0.1 mmol/L SNP or 0.005, 0.01 mmol/L H₂O₂ could alleviate NaCl stress damage and had obvious effects. The best effect was observed in the treatment of 0.1 mmol/L SNP or 0.01 mmol/L H₂O₂. After 96 h stress, the content of chlorophyll in leaves under SNP and H₂O₂ stress respectively incresased 22.05% and 19.58% comparing with single salt stress. The interaction treatment with them could significantly enhance the ability of anti-salt. When the salt stress at 96 h, the content of chlorophyll increased 29.96%, which could reduce the degradation reaction of chlorophyll in leaves.2. Under the salt stress condition, the germination of woad seed was inhibited. After 48 h, seed began to germinate. However, the effect of NO or H₂O₂ and interaction with them on the germination rate, germination potential, germination index and activity index was more obvious than 100 mmol/L NaCl treatment. Moreover, the final germination rate was respectively 49%,42.33% and 60.33%. The discrepency of interaction was highly significant(P< 0.05). The NO, H₂O₂ and interaction treatment also effectively promoted the water contents of roots and leaves under salt stress. Comparing with NO, H₂O₂ and interaction treatment, the water contents of roots respectively incresased 6.4%, 22.27% and 21.69%, meanwhile, the water contents of leaves respectively incresased 17.23%,22.64% and 30.92%. Interaction treatment with NO and H₂O₂ also had enhancement actions. After 120 h salt stress, root activity under interaction condition increased 32.39% comparing with single salt treatment.3. Different conditions of SNP and H₂O₂ also had different induced effects on antioxidant enzymes in woad. Applying the 0.1 mmol/L SNP, 0.01 mmol/L H₂O₂, the activity of antioxidant enzymes increased, but with lengthening the stress time, the activity reduced. The results indicated that SNP and H₂O₂ had a certain adjustment range, however, interaction treatment could enhance the activity, mainly resulted in the increasement of CAT and APX. When salt stress at 24 h, the activity of APX increased 63.86% under interaction condition comparing with CK. At the beginning of salt stress, the activity of CAT increased 35.63% under interaction condition comparing with CK.4. The function of exogenous NO and H₂O₂ on the osmotic adjustment substances in salt-stress woad seedlings was also investigated. The mix-solution of SNP and H₂O₂, which showed a much better protective impact than 0.1 mmol/L SNP or 0.01 mmol/L H₂O₂, could significantly increase the content of Proline in leaves, and the damage of woad seedlings caused by salt stress was alleviated effectively. The concentration of MDA as well as membrane permeability was enhanced under salt stress. The above parameters were decreased obviously by the inclusion of the mix-solution, which suggested it alleviated membrane lipid peroxidation more obviously than SNP or H₂O₂, decreased electrolyte leakage, and maintained cell membrance integrity. Salt stress increased the contents of reactive oxygen species (ROS) and decreased the activities of antioxidant enzymes. Compared to the treatment with salt only, addition of The mix-solution to the salt treatment significantly decreased the contents of H₂O₂ and the production rate of superoxide anion(O₂^·-), and remarkably enhanced the activities of antioxidant enzymes (including SOD, CAT , POD, APX and GR). The mix solution of SNP and H₂O₂ could have a big potential for reduction of oxidative damage to woad seedling leaves under salt stress.