| The effects of nitrogen applying amount and the ratio of basal: top dressing N on starch and yield formation in wheat (Tr. aestivum L.) for different end uses, ie strong gluten type variety Wanmai 38, medium gluten type varieties Yangmai 10 and Huaimai 18, weak gluten type varieties Ningmai 9 and Jiangmai 1, were studied on the Experiment Field of Crop Cultivation and Physiology Key Laboratory of the Ministry of Agriculture, Yangzhou University in 1999-2001. The main results were as follows.1. Starch content, amylose/amylopectin ratio, starch accumulating dynamic, soluble sugar content in flag leaves and grains after anthesis, branch enzyme activities among different varieties for special end uses were significantly different. With the same nitrogen applying amount and the ratio of basal: top dressing N, Yangmai 10 had the highest amylose content, Ningmai 9 had the highest amylopectin and total starch contents, and Huaimai 18 had the greatest ratio of amylose to amylopectin. The content and the accumulated amount of amylose, amylopectin and total starch in strong grains and weak grains showed "S" type dynamic change. Amylose accumulating rate of strong grains reached its peak on 25-30th day after anthesis (DAA). The accumulation rate of amylopectin and total starch reached peaks on the same time, ie 20-25th DAA. The accumulation rate of amylose, amylopectin, total starch in weak grains all reached peaks on 20-25th DAA. Logistic equation could be used to match the starch accumulation dynamics of strong and weak grains. The accumulation of amylopectin was earlier than that of amylose. On 20-25th DAA, the content of total soluble sugar and sucrose in flag leaves reached the maximum value. The content of total soluble sugar and sucrose in grains decreased from 5th DAA to maturity. Q enzyme activity in strong grains reached its peak on 10th DAA, while in weak grains reached the highest on 5th DAA. The expression time of Q enzyme activity in strong grains was later than that in weak grains.2. Starch granules in wheat grain endosperm cells were single-granule type. The starch granules in both dorsal and ventral sides of grains in strong gluten wheat were wrapped by the protein sheath, the number of protein sheaths around starch granuleswas more than that in medium gluten wheat and weak gluten wheat. The starch granules in dorsal side were mainly types I and II ,but in ventral side mainly types II and III.The formation of starch granules in the dorsal side was earlier than in ventral side of grains, and the filling was better. The flour peak viscosity of Yangmai 10 was the highest, while that of Wanmai 38 was the lowest. Among varieties, amylose content and amylose/amylopectin ratio were significantly positively correlated with setback value, respectively(r =0.8732,r =0.9759).3. Regulation of nitrogen fertilizer on starch content, amylose/amylopectin ratio, starch accumulating dynamic, soluble sugar content in flag leaves and grains after anthesis, branch enzyme activity among different wheat varieties for special end uses was significant. For Wanmai 38 , Yangmai 10, Huaimai 18,Jianmai l,the amylose, amylopectin and total starch contents decreased with the increase of applied nitrogen amount or the percentage of top dressing N . The effect of nitrogen on amylose content in Ningmai 9 was different from other varieties. But the amylopectin ,total starch contents of Ningmai 9 had the same trends with other varieties. The content of total soluble sugar and sucrose in flag leaves increased, but the contents of total soluble sugar and sucrose in strong and weak grains decreased when the applied nitrogen amount increased or the percentage of top dressing N raised.4. The protein accumulation amount increased and the number of small starch granules decreased when the nitrogen applying amount increased or the percentage of top dressing N raised. The peak viscosity of Wanmai 38 increased, and setback value decreased when the percentage of top dressing N raised. The peak viscosity and setback value of Yangmai... |
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