Effects Of Different Exogenous Substances On Waterlogging Tolerance Of Wheat

Waterlogging is one of the main natural disasters affecting the growth and development of wheat.In the middle and lower reaches of the Yangtze River in China,there is more rain in the middle and late growth and development of wheat,and the yield of wheat will be seriously reduced after suffering serious waterlogging.A large number of studies have found that spraying exogenous substances such as methyl jasmonate,melatonin,salicylic acid and betaine can promote the growth and development ability of crops under stress,improve the resistance of crops,and achieve the effect of stablilizing yield and maintaining yield.Therefore,field and pot experiments were conducted in this study,Yangmai 16 was used as the experimental material.In the field experiment,except the treatment W without spraying exogenous substances,there were 15 treatments with spraying exogenous substances.The effects of spraying combinations exogenous substances including Yuehu,earthworm enzyme,potassium dihydrogen phosphate,methyl jasmonate,betaine,melatonin and other combinations before and after waterlogging stress during flowering period on SPAD value of flag leaf,photosynthetic characteristics of flag leaf,dry matter accumulation,storage material retransportation,yield components,grain quality,and nitrogen transport before antheesis and nitrogen reaccumulation after anthesis were studied.The pot experiment further studied the effect of spraying treatments selected in the field on the mitigation effect and physiological mechanism of the waterlogging stress at the seedling stage of wheat.Finally,based on the results of field and pot experiments,three exogenous substances spraying schemes with better effect were screened out before and after waterlogging stress,providing a theoretical basis for alleviating waterlogging in production.The main research results are as follows:1.Effects of different exogenous substances on wheat yield,quality and grain nitrogen accumulation under waterlogging stressCompared with the treatment W without spraying exogenous substances,the basic component of spraying exogenous substances treatment before waterlogging is earthworm enzyme polypeptide solution,the core component contains betaine（Q2）,methyl jasmonate（Q3）,γ-aminobutyric acid（Q4）and the basic component of spraying exogenous substances treatment after waterlogging is earthworm enzyme polypeptide solution,the core ingredient contains betaine（Q2）,methyl jasmonate（Q3）,and melatonin（Q5）significantly increased the post-anthesis photosynthetic assimilation amount and the contribution rate to grain after waterlogging stress,and increased the 1000-grain weight and yield of wheat,compared with W,the yields of Q2,Q3 and Q4 treatments before waterlogging stress increased by13.2%,14.2%and 11.1%,respectively.The yields of Q2,Q3 and Q5 treatments after waterlogging stress increased by 11.3%,11.8%and 12.8%,respectively.In addition,spraying Q2,Q3 and Q4 treatments before waterlogging stress and spraying Q2,Q3 and Q5treatments after waterlogging stress increased the wheat bulk density,grain hardness,crude protein content,wet gluten content and sedimentation value of wheat after waterlogging stress,improved the quality of wheat after waterlogging stress,and significantly increased the post-anthesis nitrogen accumulation and its contribution rate to grain.2.Effects of different exogenous substances on wheat plant biomass,SPAD content and photosynthetic characteristics under waterlogging stressAccording to the results of field and pot experiments,compared with the treatment W without spraying exogenous substances,the basic component of spraying exogenous substances treatment before waterlogging is earthworm enzyme polypeptide solution,the core component contains betaine（Q2）,methyl jasmonate（Q3）,γ-aminobutyric acid（Q4）and the basic component of spraying exogenous substances treatment after waterlogging is earthworm enzyme polypeptide solution,the core ingredient contains betaine（Q2）,methyl jasmonate（Q3）,and melatonin（Q5）significantly increased the chlorophyll content of wheat leaves,increased the net photosynthetic rate（Pn）and stomatal conductance（Gs）of wheat leaves,and improved the maximum photochemical efficiency（Fv/Fm）and actual photochemical efficiency（ФPSII）of wheat,enhanced the photosynthetic capacity of wheat leaves,enhanced the resistance to waterlogging stress,and significantly increased the fresh weight and dry weight of wheat plants.3.Effects of different exogenous substances on antioxidant capacity of wheat under waterlogging stressAccording to the results of pot experiment,compared with the treatment W without spraying exogenous substances,the basic component of spraying exogenous substances treatment before waterlogging is earthworm enzyme polypeptide solution,the core component contains betaine（Q2）,methyl jasmonate（Q3）,γ-aminobutyric acid（Q4）and the basic component of spraying exogenous substances treatment after waterlogging is earthworm enzyme polypeptide solution,the core ingredient contains betaine（Q2）,methyl jasmonate（Q3）,and melatonin（Q5）significantly reduced the content of MDA,the production rate of superoxide anion O₂^-and the content of H₂O₂ in leaves.Compared with CK and W,the activities of superoxide dismutase（SOD）,catalase（CAT）,ascorbate peroxidase（APX）and glutathione reductase（GR）in leaves of wheat were increased,the contents of soluble sugar and free amino acids in leaves of wheat were increased,the degree of membrane lipid peroxidation of wheat was effectively reduced,the osmotic adjustment ability and antioxidant ability of wheat were improved,and the waterlogging tolerance was enhanced.To sum up,the treatment with the earthworm enzyme polypeptide solution as the basic component on improving wheat waterlogging tolerance is better than the treatment with the basic component eucare.In addition to the basic component of earthworm enzyme polypeptide liquid,the core components GB,Me JA and GABA in Q2,Q3 and Q4 spraying treatments can play a good induction effect before waterlogging stress,so as to improve the waterlogging tolerance of wheat and better deal with the later waterlogging stress.Among them,the Q3 treatment with Me JA as the component has the best effect.Spraying treatments Q2,Q3 and Q5 after waterlogging stress showed the same trend,which was mainly manifested as the remedial effect after waterlogging.The Q5 treatment with MT as the core component had the best effect.Treatments Q2 and Q3 could effectively improve the waterlogging tolerance of wheat before or after waterlogging.