Studies on Regulating Effect of Nitrogen Rates on Starch Granule Distribution in Grain of Wheat
|School||Nanjing Agricultural College|
|Course||Crop Cultivation and Farming System|
|Keywords||Wheat Nitrogen application rates Yield Starch granule Quality|
Based on field experiments from 2008～2010, two winter wheat cultivars Ningmai13 (low-protein content) and Xumai31 (high-protein content) were used to explore effects of nitrogen rates on grain yield, flour quality and their formation. The main results were as follows:1. Effects of nitrogen rates on grain yield and accumulation and distribution of dry matter in wheatGrain yield of both cultivars were increased gradually with the nitrogen amount from 0～225 kg hm’2, while no significantly increase of grain yield was found under 300 kg hm-2 nitrogen application, thereinto,150 kg hm-2 nitrogen application showed the highest 1000 kernels weight. Accumulations of dry matter after anthesis and its contribution to grain weight were increased with increasing nitrogen rates. Photosynthetic pigment content of flag leaf in both cultivars were increased with increasing nitrogen rates, which indicated that higher nitrogen application can effectively ellivate the sensences during later stage.2. Effects of nitrogen rates on protein and accumulation and distribution of nitrogen in wheatThe protein content during grain filling stage showed a "high-low-high" tendency, the contents of total protein, albumin, gliadin, glutenin and glutenin macropolymer (GMP) were increased with raising of nitrogen application, but globulin showed little change. Accumulation of nitrogen was increased and then reduced with nitrogen application under 0～300 kg hm-2, reach the highest under 225 kg hm-2 nitrogen application. Distribution of nitrogen showed different in different organs, from the highest to lowest in rank, they are: grain, stem and sheath. Under 0～225 kg hm-2 nitrogen application, remobilization amount, remobilization efficiency and contribution of remobilization amount of nitrogen accumulated pre-anthesis to grain nitrogen amount were increased with increasing nitrogen application, which increased grain protein content.3. Effect of nitrogen rates on starch content and starch granules size distribution in wheat Starch and starch component (amylose and amylopectin) content showed a "S" curve. During earlier period of grain filling, the accumulation rate of amylopectin was higher than amylose, while at later period the accumulation rate of amylose was higher than amylopectin, so the ratio of amylose to amylopectin displayed a "V" curve. Starch and amylase content were reduced with nitrogen application, but amylopectin content was increased. The ratio of amylose to amylopectin was increased with raising of nitrogen application, showed amylose increases faster than amylopectin after nitrogen rates. The mean diameters by volume, number and surface aera were reduced with rasing of nitrogen application during the mid and late grain filling stage, but at maturity, number and surface area of unit weight in both cultivars, Ningmai 13 was increased, and Xumai 31 was reduced. Based on the response of starch granule size distribution to nitrogen, Ningmai 13 showed better tolerance than Xumai31.4. Effects of nitrogen rates on grain qualityCrystallinity was increased and then decreased with increasing of nitrogen rates from 0-300 kg hm-2 in both cultivars, but 20 diffraction peaks were decreased. Swelling power of flour was highest at N150, and showed the against tendency with the amount of nitrogen. Wet and dry gluten content, SDS-sedimentation volume and falling number were significantly increased with nitrogen application. Trough Viscosity, Final Viscosity and Setback of flour were increased in both cultivars with increasing nitrogen, Breakdown was reduced. The purified starch pasting properties closely related with genetype of wheat.5. Relationships of wheat grain starch composition and starch pasting propertiesThe correlative analysis results indicated that there were close correlations between wheat starch composition, which include amylose, amylopectin, granule size distribution and starch pasting properties. Peak Viscosity, Trough Viscosity, Breakdown and Final Viscosity of flour were significantly positive correlated with the volume, number and surface area percent of B-type starch granules, and were negatively correlated with A-type and B-type starch granules.In conclusion, higher nitrogen application improve grain yield, amylose and protein content of wheat, the mean diameter of both cultivars were reduced, starch granule number and surface area unit weight were showed the against tendency, and effected by different genotypes and different nitrogen applications. Wet gluten, dry gluten, SDS- sedimentation volume, falling number, Trough Viscosity, and Final Viscosity and other quality indicators were promoted with nitrogen rates, and then improving the grain quality of wheat.