Physicochemical Bases Of Starch Development In Wheat Grains And Its Response Mechanism To Nitrogen Fertilizer

Based on the field experiments on non-waxy wheat cultivars applied in production and waxy wheat varieties, the differences of starch granule development in grain endosperm cells, grain starch accumulation dynamics and amylopectin chain length distribution among different genotypes and their relationship to wheat flour characteristics were examined. The physiological basis of starch synthesis was also studied. Composition of waxy protein sub-unit and its relations to amylose content and swelling power in different wheat varieties were analyzed. Effects of nitrogen fertilizer on physicochemical characteristics of starch formation and relevant mechanism were also studied, which could provide more knowledge about starch synthesis mechanism and supply theoretical reference for producing wheat with good grain quality. The main results were as follows.1 Dynamics and differences of grain starch accumulation, starch granule structure in different wheat varieties were studied. The results showed that amylose, amylopectin and starch contents in grains rose gradually after anthesis. The maximum accumulating rate of amylose appeared on the 25-30^th day after anthesis (DAA), while that of amylopectin appeared on the 20-25^th DAA. Amylose, amylopectin and starch accumulating rates of waxy wheat Yang 0369 were lower than those of the others from 15^th to 30^th DAA, therefore its grain weight was the lowest. Starch granule structure in grain endosperm cells of wheat varieties Yangmai 13, Yang0369 and Zhongyou9507 was observed by use of scanning electronic microscopy during the grain filling period. Only did a few starch granules appear in endosperm cells on the 5^th DAA. The number of type I starch granules increased mainly at early grain filling stage (5-10DAA). Then mastoid protuberance started to appear on the surface of type I starch granules and developed into type II starch granules. The number of type II starch granules rose mainly at the middle and late grain filling stages. Type I and II starch granules kept...