Effects Of Combined Application Of Exogenous Abscisic Acid And Hydrogen Peroxide On Salt Tolerance Of Festuca Arundinacea

Salt stress is one of abiotic stresses frequently occurred on the earth,which can cause serious damage to the growth and development of plants.Tall fescue（Festuca arundinacea）is a high-quality cool-season turf-grass with salt tolerance to a certain extent and can be applied to saline-alkali land improvement and restoration.Abscisic acid（ABA）and hydrogen peroxide（H₂O₂）are important stress-signaling molecules which could enhance plant stress resistance at appropriate concentrations.In order to reveal the influence and concentration effect of exogenous ABA and H₂O₂spraying on the salt tolerance of tall fescue,the following three experiments were carried out using commercial variety of"Phoenix No.2"as the tested material and simulated salt stress with sodium chloride（Na Cl）solution:（1）Under the salt stress of Na Cl（0,50,100,150m M,respectively.）,the impact and concentration effect of different concentrations of exogenous ABA spraying on tall fescue for salt tolerance enhancing was studied;（2）The effect of exogenous H₂O₂addition on the salt tolerance of tall fescue and the spraying concentration gradient for salt tolerance improving were studied by measuring the morphological and physiological indexes of tall fescue after spraying with different concentrations of exogenous H₂O₂under the Na Cl resolution of 100m M.（3）Based on the conclusions of experiments（1）and（2）,the effect of combined application of ABA and H₂O₂on the salt tolerance of tall fescue were studied by sand culture method.The main results are as follows:（1）Under salt stress,ABA guarantees the normal growth and morphological structure by increasing the leaf area,leaf length,root area and root diameter of tall fescue,and meanwhile maintains the normal relative water content of leaves,reduces the degradation of chlorophyll content and maintains the stability of cell membrane structure,reduces the relative electrical conductivity to maintenance the normal physiological metabolic activities in F.arundinacea,thereby effectively improving the salt tolerance of tall fescue.（2）Under the stress of 100 and 150 m M Na Cl,respectively,the effect of ABA spraying concentration on the salt tolerance of tall fescue was generally appeared a trend that salt tolerance increased with concentration increasing first and then decreased with the spraying concentration further increasing.Under the stress of 100m M Na Cl,plant height,leaf area and chlorophyll content of tall fescue sprayed with50μM ABA were significantly higher than that in distilled water spraying（P<0.05,the same below）,and the relative conductivity is significantly lower than that in distilled water spraying treatment.Under the stress of 150 m M Na Cl,plant height,leaf length and relative water content of tall fescue sprayed with 50μM ABA were significantly higher than those in distilled water spraying,and relative conductivity was significantly lower than that in distilled water spraying.Through comprehensive evaluation with the membership function method used,50μM ABA spraying had the better ability than other concentrations to improve the salt tolerance of tall fescue.It is an effective method to alleviate the stress of Na Cl pressure and finally improve its salt tolerance.（3）Foliar spraying of H₂O₂is an effective measure to enhance the salt tolerance of F.arundinacea,by alleviating the hindrance of salt stress on the leaves and roots of tall fescue,maintaining cell membrane stability,increasing proline content in leaves to strengthen osmotic regulation and other physiological processes;In this study,5 m M H₂O₂spraying performed better than other concentrations,among which plant height,leaf area and leaf proline content were significantly higher than those in distilled water spraying,and 5 m M H₂O₂addition was more appropriate concentration to enhancing the salt tolerance of F.arundinacea.4)The combined application of exogenous ABA and H₂O₂has a stronger effect to alleviate the harm caused by salt stress to the growth of F.arundinacea.than single spraying of ABA or H₂O₂,which is mainly manifested as increasing in plant height,leaf length,leaf area,leaf width,root area and root length of F.arundinacea to various extent under the combined application treatment than that spraying them alone.（5）Compared with spraying ABA or H₂O₂alone,it can more effectively reduce the degree of damage and peroxidation of cell membranes.However,for the relative water content and proline content in leaves,the effect of combined application of ABA and H₂O₂is worse than that of spraying them alone.The effect of mixed application on the salt tolerance indexes of F.arundinacea.was comprehensively analyzed,and the effect of combined application on the salt tolerance of tall fescue was stronger than that of spray ABA and H₂O₂only.