In order to study the effects of high temperature on grain filling and yield of winter wheat during grain filling stage,a heat resistant variety Huaimai 33 and a heat sensitive variety Huacheng 3366 were treated with high temperature during grain filling stage(14-20 days after anthesis),with the wheat grown at natural temperature in the field as control,to study the effects of high temperature on chlorophyll content,antioxidant enzyme activity,malondialdehyde(MDA) content,sugar content in flag leaves,starch content,key enzymes activity of starch synthesis in grains,and the grain weight and yield of wheat.The results showed that high temperature significantly reduced the chlorophyll content of Huaimai 33 and Huacheng 3366 flag leaves by 5.88% and 9.86%,respectively,reduce the activity of antioxidant enzymes,but increased the content of MDA,soluble sugar and sucrose in wheat flag leaves. High temperature treatment also significantly decreased the activities of ADPG pyrophosphorylase(AGPase),bound starch synthase(GBSS),soluble starch synthase(SSS) and starch branching enzyme(SBE) in the grains of the two varieties,and decreased the content of amylopectin and total starch. The total starch content of Huaimai 33 and Huacheng 3366 decreased by 5.63% and 8.77%,respectively. High temperature treatment mainly reduced the grain weight of the third spikelet position of Huaimai 33 and the grain weight of the first,second and third spikelet positions of Huacheng 3366. The yield of Huaimai 33 and Huacheng 3366 in 2018-2019,2019-2020 was decreased by 5.07% and 16.33%, 6.23% and 8.90%,respectively. Compared with the high temperature sensitive variety Huacheng 3366,the heat resistant variety Huaimai 33 was less affected by high temperature. In conclusion,high temperature treatment during grain filling stage significantly reduced the chlorophyll content and antioxidant enzyme activity of flag leaves,affected the transport of carbohydrates in leaves,and led to the decline of key enzyme activity of starch synthesis,starch content and yield. |