The Regulating Mechanism Of Exogenous Nitric Oxide On Cold-resistance Of Wild Poa

Nitric oxide(NO) is a kind of high molecular biological signal, it is related with theform and development of plants、programmed cell death、stomatal closure、cellularantioxidant and antiviral defense.NO also can be used as multifunctional molecule playing acentral role in mediating a variety of physiological processes and responses to biotic andabiotic stresses including cold. In addition to facilitating the growth of plant. Temperature isone of the most important factor on plant growth, especially freezing temperatures that area constraint to development of the lawn grass industry in northern China.However,information is lacking on NO and their roles in wild Poa. under cold stress. Therefore, in thepresent experiment, two kinds of wild bluegrass was tested, they were all collected in Gansuprovince. NO-donor SNP was used in antioxidative system and nitrogen and carbonmetabolism under cold stress, Study NO physiological regulation function of cold resistanceof wild Poa. leaves under cold stress.The main results were as follows:1. In0~700umol/L concentration range, with the increase of the SNP concentration,ground biomass, growth rate and recovery increased first and then decreased; relativemembrane permeability and free proline decreased first and then increased, soluble sugarand soluble protein content increased first and then reduced; The activity of SOD, POD andCAT of bluegrass increased first and then decreased. The results implied that, comparedwith other concentrations, at100umol/L of SNP, the bluegrass plants accumulated thegreatest amount of osmotic regulation substances in the plants, and least damage happenedto the membranes, thus this concentration had the best alleviation effect.2. Low temperature inhibits the growth and development of the germplasms, reducedthe volume of plants, the growth rate is reduced, the earth recovery rate reduced, spraying100umol/LSNP relieve the injury of Kentucky bluegrass under low temperature, increasethe amount of plants of Kentucky bluegrass, speed up its growth and development, improvethe recovery rate.3.With the decreasing of temperature stress, Kentucky bluegrass relative membranepermeability of leaf and Pro content increases, SS and SP contents are lower. ExogenousNO treatment to alleviate the injury of Kentucky bluegrass under low temperature, reducethe relative membrane permeability of Kentucky bluegrass and Pro content, increase thecontent of SS and SP.4.Induced in Kentucky bluegrass leaves, hydrogen peroxide (H2O2) and hydroxylradical (OH-) content and superoxide free radical (O2-) producing rate increased significantly, and increase the product membrane lipid peroxide malondialdehyde (MDA)accumulation. Spraying100umol/L SNP reduce the content of H2O2, OH-and O2-producing rate and membrane lipid peroxidation, easing the oxidative damage induced bylow temperature stress.5.Low temperature treatment improved the Kentucky bluegrass leaves of SOD, POD,CAT, ascorbic acid peroxidase (APX) and glutathione reductase (GR) activity. ExogenousNO treatment to alleviate the injury of Kentucky bluegrass under low temperature, tofurther improve the Kentucky bluegrass leaves of SOD, GPX, APX, GR, and CAT activity.6. Cold stress reduced the contents of PSⅡpotential fluorescence efficiency (Fv/Fo),PSⅡmaximum fluorescence efficiency (Fv/Fm), the actual photochemical efficiency of PSⅡ(ΦPSⅡ)and photochemical quenching (qP), improved the non-photochemical quenching(NPQ). Application of SNP also increased the contents of Fv/Fo, Fv/Fm,ΦPSⅡand qP,reduced NPQ.7.Exposure of wild Poa leaf to cold stress caused free amino acid accumulation.Further, treatment of wild Poa leaf to cold stress resulted in a marked decrease in nitratecontent, nitrate reductase(NR), glutamine synthetase(GS) and glutamate-oxoglutarateaminotransferase (GOGAT) activities and an increase in ammonium content and glutamatedehydrogenase(GDH) activity. By contrast, addition of exogenous nitric oxide together withcold stress can raise nitrate content, NR, GS and GOGAT activities in leaf, while it sloweddown ammonium content and GDH activity. These dates suggested that NO could improvecold tolerance in plants by enhancing nitrogen metabolism.8.Starch contents were significantly increased in cold-stressed leafs, but sucrose、fructose and glucose contents was low in comparison with normal leafs. Cold stressenhanced the activity of sucrose synthase and soluble invertase in leaf of wild Poa leaf,while sucrose phosphate synthase (SPS) activities were slightly lower than normal leafs.Exogenous nitric oxide improved sucrose content and the activity of sucrose phosphatesynthase, decreasd the starch content,and the activity of sucrose synthase and soluble acidinvertase, while neutral invertase were not significantly affected in leaf of cold-stressed leaf.It is concluded that exogenous NO treatment on wild Poa may be a good option to reducecold injury by regulating carbohydrate metabolism in leaves.9.Spraying water and SNP, with the extension of low temperature stress, relativemembrane permeability, content of praline, H2O2, OH, MDA content and the productionrate of O2.-, SOD, POD, CAT, APX and GR activity, NH4+-N content, GDH activity, AI,NI and SuSy activity all increased first and decreased when the temperature was20℃. Solublesugar, soluble protein, chlorophyll and NO3--N content, NR, GOGAT, GS and SPS activitydecreased first and increased when the temperature was20℃. Spraying SNP, the recoveredprocess is faster then spraying water.