The Biological Effects Of Exogenous Nitric Oxide On Seed Germination And Stress Resistance Of Pinus Tabulaeformis

Nitric oxide (NO) is a kind of signal transduction molecules. It plays an important role in the plants, which involved in respiration, photomorphogenesis, seed germination, root growth, development of fruit mature and aging, resistance and so on. At present NO research on improving resisitance of the tree is less. In the paper, the effects of exogenous NO on germination under osmotic stress and resistance of seedling of Pinus tabulaeformis were studied. We used Chinese pine as materials, PEG-6000solution to simulate drought stress, the NaCl solution to simulate salt stress, sodium nitroprusside (SNP) as NO agents, cPTIO and hemoglobin as NO scavenger, and studied the physiological change of seed germination and seedling growth under stress. The main results were as follows:1. Seed germination of Pinus tabulaeformis was inhibited under osmotic stress (-0.5MPa), the germination rate dropped and radical elongation was severely inhibited.The Pinus tabulaeformis seeds were treated with exogenous NO donor SNP under osmotic stress, the results indicated that:the effect of SNP was different as the concentration different, low concentration NO (0.1-0.3mmol/L SNP) effectively relieved the influence of osmotic stress, promoting seed germination, while high concentration NO (more than0.5mmol/L SNP) inhibited it.0.lmmol/L SNP was the best concentration.2. The promotion of exogenous NO was relevant to nutrient metabolism in the seeds. Exogenous NO (0.1mmol/L SNP) greatly improved amylase and protease activity and increased soluble sugar and soluble amino acids content in Pinus tabulaeformis seeds under osmotic stress, providing the needed nutrients for seed germination. With the NO scavenger cPTIO, the translation of nutrients in Pinus tabulaeformis seeds under osmotic stress was delayed, the promotion of exogenous NO was reversed.3. With Exogenous NO (0.2mmol/L SNP) pretreatment, it promoted superoxide dismutase (SOD) activity and reduced superoxide anion radical (O2(?)), hydrogen peroxide (H2O2) and malondialdehyde (MDA) content in Pinus tabulaeformis seedlings leaves under drought stress, it also promoted the synthesis of proline and chlorophyll and enhanced Nitrate Reductase activity. All this suggested exogenous NO could effectively alleviate the membrane peroxidation, strengthen the regulating ability of penetration of the cell and maintain N and C metabolism in plants.4. The accumulation of reactive oxygen was caused by salt stress (150mmol/L Nacl-1/2Hoagland) in Pinus tabulaeformis seedlings leaves. With the appropriate concentration of the exogenous NO (0.2mmol/LSNP) treated, it significantly delayed the rising trend of O2(?), H2O2and MDA under salt stress and reduced the content of O2(?), H2O2and MDA. It also promoted proline and soluble protein content of Pinus tabulaeformis seedlings leaves, with NO scavenger hemoglobin (Hb) coprocessinged the NO effect was reversed and the accumulation of reactive oxygen aggravated.