Cytological Structure Of Flag Leaves And Awns In Relation To Their Photosynthetic Characteristics In High-yield Genotypes Of Wheat

Since the flag leaf assimilates are the most important contributor to the dry weight accumulation in grains, improving photosynthetic capacity of flag leaf in order to increase wheat yield has been the subject of many studies. However, most of the previous studies examined physiological and biochemical characteristics, few studies have focused on their cytological traits. In this study, we took maternal parent Xiaoyan 54, paternal parent 8602 and the offspring Xiaoyan 81 as materials. Leaf thickness, the size of vascular bundles and cytological features of mesophyll cells, chloroplasts in three genotypes were investigated by means of transverse sectioning, and leaf maceration. The results of transverse sections showed that the leaves of Xiaoyan 81 were thicker than that of Xiaoyan 54 and 8602, the area as well as the perimeter of middle vascular bundle was larger in Xiaoyan 81 as compared with Xiaoyan 54 and 8602. By means of cell maceration, morphology of the mesophyll cells was described. It was found that mesophyll cells contained more protuberances and the percentage of mesophyll cells possessing more than six protuberances was higher in Xiaoyan 81 than that in Xiaoyan 54 and 8602. Furthermore, the size of mesophyll cells and the number of chloroplasts per cell was larger in Xiaoyan 81 than the cells contained equal protuberances in Xiaoyan 54 and 8602. All the results described here demonstrated that the characteristics of mesophyll cells were optimized in the process of wheat breeding, suggesting that the ultrastructural characteristics of chloroplast and the content of polysaccharide are closely linked to the photosynthetic efficiency.In general, the photosynthesis organs in wheat were considered as two parts, leaves and non-leaf organs. The leaves particularly flag leaves, have been considered to be the key organ contributing to higher yields, whereas non-leaf organs have been considered subsidiary organs, however, many studies have been reported or suggested the considerable contribution to the yield of non-leaf organ. Compared to extensive investigations on the assimilation contribution of leaves, the photosynthetic characteristics of awn - an important part of non-leaf organs, have not been well...