Study On The Physiological Mechanism Of Chemical Regulation Technology To Alleviate The Harm Of Wheat Fost-anthesis High Temperature

High temperature is one of the important meteorological disasters in the southern part of Huang-Huai-Hai.From April to June,high temperature heat damage seriously affected grain filling characteristics and reduced yield and quality in Huang-Huai-Hai wheat area.In this study,16 main wheat varieties in southern Huang-Huai-Hai wheat region,including Annong 0711,Huai 33 and Luo 26,were selected as materials to screen high temperature resistant varieties in 2017-2018.Huai 33 and Annong 0711,widely cultivated varieties in Anhui Province,were selected to study the physiological mechanism of reducing high temperature by chemical adjustment techniques,the plastic film covering method was subjected to high temperature treatment(about 5 degrees above atmospheric temperature)at 12 to 18 days after anthesis,the effects of 24-epibrassinolide(EBR)and potassium dihydrogen phosphate(KH2PO4)on high-temperature hazards were applied to the high-temperature.The aim is to select the heat resistant varieties suitable for planting in the southern part of Huang Huai Hai,and to find out the suitable blending and spraying time to alleviate the high temperature heat damage during the filling period,and to provide the theoretical basis for the high temperature heat damage adjustment techniques of winter wheat in the later stage of Huang Huai Hai winter wheat.The main findings are as follows:1.According to the sum of 1000-grain weight and yield thermosensitivity index,16 wheat varieties were screened with different heat-resistant types.Zhou 27,Cun 5,Anong 0711,Luohan 19,Xinke 169,Zheng 136,Liangxing 99 and Huai 33 were selected as heat tolerant varieties,Zhong 175,Zheng 7698,Zhong 895,Zhou 32,Bainong 207,Luohan 22,Huacheng 3366,Luomai 26 is a thermal sensitive variety.2.Post-anthesis high temperature stress significantly decreased chlorophyll content,Pn,chlorophyll content and SOD,POD,CAT activity in flag leaf,increased MDA content,aggravated membrane lipid peroxidation,and accelerated senescence of flag leaf in wheat(Triticum aestivum L.).There were significant differences in Pn,chlorophyll content and canopy temperature between 20 days after anthesis(high temperature)and 30 days after anthesis(after high temperature),and the decrease of Pn,SPAD value was more obvious at 30 days after anthesis.3.High temperature after anthesis reduces yield and affects grain quality.Post-anthesis high temperature stress significantly reduced the number of grains per panicle,1000-grain weight and yield,but had no significant effect on panicle number.Post-anthesis high temperature stress increased grain protein content,bulk density,wet gluten content,formation time,stabilization time and water absorption,and changed powdery parameters.4.Foliar spraying of KH2PO4 and EBR to mitigate high temperature hazard.The application of KH2PO4 and EBR on the leaves of the leaves significantly affected the flag leaf Pn,SPAD,canopy temperature,flag leaf SOD,POD,CAT activity and MDA content.Compared with EBR,KH2PO4 could increase the value of Pn and SPAD in flag leaf,decrease the content of MDA,and delay the senescence of flag leaf.Spraying KH2PO4 and EBR on winter wheat before and after high temperature,respectively,could increase grain number per ear,1000-grain weight and yield,which could alleviate the influence of high temperature to a certain extent.Both KH2PO4 and EBR had the best effect before and after high temperature heat damage.