Post-Anthesis Photosynthetic Assimilation and the Changes of Carbon and Nitrogen in Different Varieties of Spring Maize

Abstract

Dry matters production after anthesis is very important for maize yield.To further clear its role in super high yield con-dition(high density with ample water and fertilizer supply),we compared yield components in three cultivated varieties,including Denghai661(DH661),Zhongdan 909(ZD909) and 970.According to the theory of yield performance,the post-anthesis yield performance parameters were analyzed.The changes of net photosynthetic rate,the contents of chlorophyll,soluble sugar,starch,total C and N were measured in the ear leaf.The results showed that there were significant differences in the yield among three varieties.Varieties with higher yield(DH661 and ZD909) had higher kernel weight per ear,while DH661 had more grains per ear(466.7) and ZD909 had higher 1000-kernel weight(392.7 g).The post-anthesis dry matter production and its partitive ratios in grains were both higher in the two varieties with higher yield.Yield performance analysis showed that the mean leaf area index(mLAI) and leaf area duration(LAD) were significantly and positively correlated with post-anthesis dry matter production and yield.The chlorophyll,total carbon and total nitrogen content decreased slowly and C/N ratio increased slowly in the two varieties with higher yield.The net photosynthetic rate(Pn) was relatively higher in the ear leaves in the whole grain filling stage.The photosynthate not only supplied to kernels but also stored as starch in leaves at the early phase of grain filling.Only when Pn de-clined at late phase of grain filling the accumulated starch began to degrade for the kernel filling.These results indicated that the balance between carbon and nitrogen metabolism,and slowing down the photosynthate decrease in ear leaf are responsible for maintaining higher mLAI and LAD,resulting in higher yield.