Effects of Nitrogen Fertilizer Application Rate on Starch Granule Size Distribution and Starch Pasting Properties in Wheat(Triricum aestivum L.) Grain

Wheat A-and B-type starch granules have significantly different chemical compositions and functional properties which result in the two starch granule types being utilized differently,both in food and nonfood uses.The granule size distribution of wheat starch is affected by both genotype and environment factors.Nitrogen fertilizer management plays a vital role in increasing the yield of wheat,and it has a significant effect on wheat qualities.Currently little information is available about the different distribution of starch granule size and its pasting properties in wheat under different nitrogen fertilizer application rate.The wheat cultivar Yumai 49-198,being large-scale popularized in Huang-huai wheat zone,was used to investigate the distribution of grain starch granule size and the paste property of large and small starch granules fractions under different nitrogen fertilizer application rate in Henan province in 2004-2006 growth season.The results indicated that large starch granule fractions exhibited higher peak,trough,and final viscosities relative to small starch granule fractions.Small starch granules fractions possessed higher paste time and temperature compared with the respective large starch granule fractions.The peak,trough and final viscosities of large,small starch granule fractions and total starch increased with N application rate,maximal at N3 or N4 treatment,which indicated that optimum nitrogen fertilizer application rate would improve wheat starch quality.With N fertilizer application rate increasing,the percent volume,number and percent surface area of 2.0 μm and9.8 μm starch granules decreased,while the percent volume,number and percent surface area of 9.8 μm starch granules increased.The results suggested that increased N fertilizer application rate mainly decreased the number,volume and surface area of small starch granule and increased the number,volume and surface area of large starch granule fractions.