Effects Of High Temperature And Drought Stress On Starch Synthesis Characteristics After Flowering Of Winter Wheat

In this study,two wheat varieties of different quality types(Zhengmai 366 and Yumai 49-198)were used as experimental materials to study the effects of high temperature,drought and drought stress on photosynthesis,material transport,the accumulation of non-structural carbohydrates,the quality of starch,and the key enzyme activity of starch synthesis under potting and artificial climate chamber。The biosynthesis of wheat starch and yield under different stress were analyzed.The aim of this study was to discuss the mechanism of wheat starch synthesis under adversity stress and provide the theoretical basis for wheat cultivation.The main results are as follows:1、Short-term temperature,drought and complex stress after anthesis accelerated chlorophyll degradation,reduce stomatal conductance and intercellular carbon dioxide concentration,resulting in decreased flag leaf chloroplast content,net photosynthetic rate decreased.The influence degree of each stress were high temperature and drought stress>high temperature stress> drought stress.Among different cultivars,Yumai 49-198 was more affected than Zhengmai 366.2、Adversity stress inhibited the dry matter run before flower storage,significantly reduce the amount of dry matter stored before the anthesis.But the spike axis+glume is the most affected.The influence degree of each stress were high temperature and drought stress>high temperature > drought stress.Among the two cultivars,Zheng Mai 366 was more sensitive to the stress of material transfer.3、The contents of soluble sugar,sucrose and fructose in wheat leaves,stem + leaf sheath,spike axis+glume and kernel were significantly decreased by high temperature,drought and combined stress.The effect of compound stress was the highest on the same cultivar,followed by high temperature and drought.There is a significant superposition effect.The effects of adversity stress on Yumai 49-198 were greater.4、The activity of key enzymes in starch synthesis were significantly reduced by high temperature,drought and combined stress,resulting in a decrease of starch accumulation.On the effects of key enzymes in starch synthesis and starch accumulation,the effect of high temperature was higher than that of drought,and the combined stress have superposition effect.Among cultivars,Yumai 49-198 was more affected than Zhengmai 366.5、High temperature,droughtand combined stress significantly decreased the content of amylopectin in mature period wheat grain.However,its effect on amylose content is relatively small.So it makes the ratio of amylose to amylopectin decreased significantly,starch structure changed,thus affecting the starch quality of wheat grain.Wheat starch swelling power,peak viscosity,low viscosity,breakdown viscosity and setback in the face of adversity is decreased.The influence of different treatment performs as that DS +HT > HT> DS.Compared with the two cultivars,the starch quality of Yumai 49-198 was more susceptible to stress.6、Under the experimental conditions,The stress mainly reduces Grain yield and biomass by lowering wheat grain weight.Compared the results of different stress treatment,the effect of high temperature stress on yield was greater than that of drought stress,and the combined stress had a superimposed effects on the yield.The effects of high temperature stress on the yield of Yumai 49-198 were higher than that of Yumai 366.