Effect And The Mechanism Of Chemical Agents On Stress Resisitence To Dry-hot Wind Of Winter Wheat

Dry-hot wind is one of the agro-meteorological disasters encountered in the grain-filling period,which can seriously affect the yield and quality of wheat.Learning the disaster-causing mechanism of dry-hot wind and studying the effect of new-type chemical agent on wheat stress resistance play an importance role in China's food security.In this study,the different periods and grades of dry-hot wind stress on physiology and grain weight of winter wheat were researched with the self-developed movable dry-hot wind simulator.The hazard mechanistics of dry-hot wind disaster and the response of winter wheat were clarified.Based on the natural environment and dry-hot wind simulated greenhouse environment,the regulation mechanism of different kinds of chemical agents on winter wheat against dry-hot wind were also researched.The best application period and combination formula of the chemical agents were selected,and theirregulatory mechanism on the wheat resistance to dry-hot wind were claritied.So as to provide data and technical support for enriching the hazard characteristics of dry-hot wind,and comprehensively improving their chemical disaster control capability in China.The main results and conclusions were listed as follows:1.The chlorophyll degradation of wheat flag leaf was accelerated under dry-hot wind disaster,leading the premature senescence of leaves.The dynamic balance of the antioxidant system in wheat was destroyed.It caused a large accumulation of malondialdehyde(MDA),and increasd the activity of superoxide dismutase(SOD)and peroxidase(POD),and released more osmotic adjusting materials like water soluble protein(WSP)and water soluble sugar(WSS).Dry-hot wind caused the reduction in wheat grain weight and the yield.The different damage characterics of wheat grain weight were observed under different dry-hot wind stresses: the first grain position > the second grain position > the third grain position.The degree of damage caused on grain weight by dry-hot wind in the later filling stage: mainly in the lower and middle of wheat ears,the second grain position > the first grain position > the third grain position.The damage degree of dry-hot wind suffered in the middle filling stage was higher than that in the later filling stage,and the heavy-grade dry-hot wind harmed more than the light-grade one.2.Under dry-hot wind stress,the stay-green capacity and water holding capacity of wheat leaves were improved with different chemical agents,and the promoting effect could be strengthened with the growth process.Each treatment were beneficial to maintain the photosynthetic supply intensity and supply period of winter wheat in the later filling stage,and promoted the accumulation of dry matter in the grain after anthesis.The grain filling rate and grouting duration of wheatwere all increased.The spike number,the grain number,and the kilo-grain weight were all enhanced with the different agents,thus improving the yield of wheat.Among the different type of agents,seed dressing had the best effect on increasing the spike number,and foliar spray at jointing stage had the best effect on grain number,and foliar spray at anthesis had the best effect on kilo-grain weight.3.Under dry-hot wind stress,the antioxidant capacity of winter wheat could be enhanced with different chemical agents,and could be effectively improved resistance level of wheat.Each treatment could reduced the content of MDA,indicating that the damage of cell membrane caused by excessive free radicals could be reduced.Each treatment could promoted the osmotic regulator(WSP and WSS),thus the ability of self-regulation under adverse conditions could be improved,and the protection of enzyme and biofilm could be enhanced.Each treatment increased the activity of antioxidant enzyme(SOD and POD),thus the ability of eliminate free radicals in the wheat body could be enhanced.4.The conclusion was drawn the regulation of each chemical agent on the growth and yield of winter wheat under dry-hot wind stress: Foliar spraying was better than seed dressing on improved the wheat resistance of dry-hot wind stress,and foliar spraying at anthesis was better than that at jointing stage.A synergistic effect was found with the combination treatments of seed dressing and foliar spraying,and the compounding of chemical agent in three periods was better than that in two periods.Moreover,the effect of WBH treatment(the combination treatment of dressing,foliar spray at jointing stage and anthesis)was better than other treatments.