Dynamical Changes Of Structure And Polysaccharide Of Flag Leaf Of Around Flowering In Wheat

Wheat flag leaf exerts important functions not only in photosynthetic efficiency but also in yields of grain, moreover, it is the main resource of grain carbohydrate. There are many studies on wheat flag leaf, but most have focused on physiological and biochemical characteristics, few studies have examined the dynamic changes of physiological and biochemical characteristics and structure of wheat flag leaf during different stages. In this paper, the sequential changes in the number of mesophyll cells and ultrastructure of chloroplasts as well as subcellular location and content of polysaccharide in new high-yield wheat flag leaves Xiao yan 81, which is a selected offspring from its maternal parent Xiaoyan 54 and paternal parent 8602 were investigated by means of light microscopy, transmission electron microscopy (TEM) , ultraviolet spectrophotometer together with histochemical analysis before and after anthesis.The morphology of single mesophyll cell was observed using cell separation technique under the light microscopy. The solid frame structure of a single mesophyll cell with undulate margins consists of 2-15 cell-segments or links and it can be clearly characterised as peaks and dales. Mesophyll cells with more than four-linked took about 54 percentage, which proportion was stable throughout the ontogeny.The mean number and the ultrastructure of chloroplasts per mesophyll cell were observed and counted under light microscopy and transmission electron microscopic (TEM). The chloroplast number gradually increased with anthesis stage coming and gradually dropped after reaching a maximum at milk-development period. Further analysis using Mann-Whitney's U-test revealed that difference in chloroplast number was statistically significant between florescence-emergence stage and anthesis stage (P<0.05) and this difference was the most at milk-development stage (P<0.001). TEM observation of chloroplasts indicated that the number of thylakoid per granum and the degree of grana stacks varied over a wide range in flag leaf at every stage. They developed steadily from anthesis stage and reached a peak at milk-development stage followed by a dramatic decrease, while the number and size of relative starch and lipid body increased with wheat age.