Effect of Suitable Late Sowing on Photosynthetic Performance of Weak Spring Wheat during Grain Filling Stage

To understand the effects of late sowing on photosynthetic performance of flag leaves during grain filling stage,the weak spring wheat varieties Zhengmai 9023(strong gluten),Yanzhan4110(middle gluten) and Yumai 50(weak gluten) were used as materials and sowed at different date.The result indicated that the grain yield of Zhengmai 9023 at late sowing was 8.26% lower than that at sowing on time and 4.68% higher than that at early sowing;The grain yield in average of Yanzhan4110 and Yumai 50 at late sowing were 14.38%,18.55% higher than that at sowing on time and early sowing.The leaf area index of each varieties at late sowing had no difference with that sowing on time during grain filling stage,but that of them were significantly higher than that at early sowing,with an average of 12.7%;The chlorophyll content of Zhengmai 9023 and Yanzhan4110 at late sowing were higher than that at sowing on time and early sowing,especially at 14 days after anthesis;The net photosynthetic rate of Zhengmai 9023 at late sowing was the highest all over the grain filling stage,that of Yanzhan4110 at late sowing was significantly higher than that sowing on time and early sowing at 21 days after anthesis,and for Yumai 50 was at 0~7 days after anthesis.The late sowing for the three varieties have advantage on net photosynthetic rate too.Thus,suitable late sowing can maintain better photosynthetic performance of weak spring wheat during the grain filling stage and can improve their yields.