Nitrogen Metabolism And GMP Particles Size Distribution In Grains Of Wheat In Relation To Application Of Nitrogen Fertilizer

The effects of nitrogen fertilizer rate on nitrogen metabolism and GMP particles size distribution in grains of wheat were systemically studied with two selected winter wheat cultivars, Shangnong15 with small spike and Taishan9818 with large spike, using enzymological method and biochemical analysis method. The experimentation was carried out in the experimental farm of shandong agricultural university from 2007 to 2009. The main results read as follows:1 Effects of nitrogen fertilizer rate on nitrogen metabolism of wheatNitrogen supply elevated the nitrogen accumulation amount in wheat plant. The content levels varied with the cultivars: at anthesis, the nitrogen accumulation amount in all vegetative organs of TS9818 was higher than thoes of SN15; at maturity, the nitrogen accumulation amount in spike and kernel of TS9818 was higher than thoes of SN15. The nitrogen distribution rate in kernels of SN15 decreased with increasing nitrogen supply, while the nitrogen distribution rate of TS9818 was increased. Nitrogen supply was benefit to distribute more nitrogen in kernels of TS9818, the large-spike cultivar.The nitrogen traslocation efficiency in flag leaf of Shannong15 and Taishan9818 showed decreasing tendency along with the increasing nitrogen supply, while the traslocation efficiency in other vegetative organs decreased with nitrogen supply increasing from 0-240 kg·hm^-2, when the nitrogen supply rate exceeded 240 kg·hm^-2, the nitrogen traslocation efficiency increased. Compared with Shannong15, the nitrogen traslocation efficiency in flag leaf and sheath of Taishan9818 was significantly higher, it implied that Taishan9818 had more temporary nitrogen translocated from vegetative organs to kernel than Shannong15. When applied nitrogen fertilizer at the rate of 0-240 kg·hm^-2, the NUTE of Taishan9818 derceased with the increasing of nitrogen supply. Applied more than 240 kg·hm^-2, the NUTE tended to increase.The analysis of correlation showed that the content of protein in kernel were positively correlated with the nitrogen accumulation amount at anthesis(R²=0.674), and positively correlated with nitrogen traslocation amount and efficiency(R²=0.7745 and 0.742, respectively). It implied that the higher nitrogen accumulation and superior nitrogen traslocation efficiency were the physiological basis of increasing protein content.Nitrogen supply elevated the NR and GS activity in flag leaves, the NR activity in flag leaf of Shannong15 was higher than those of Taishan9818, but the NR of Taishan9818 could be remaintained relatively high-activity for longer periods than Shannong15.Nitrogen supply decreased the proportion of albumin protein in Shannong15, but it was scarely influenced by nitrogen rate; compared with control (N0), the proportion of glutenin was decreased, but it increased gradually with the increasing nitrogen supply. The proportion of glutenin and gliadin of Taishan9818 was increased within the nitrogen rates from 0 to 240 kg·hm^-2, while decreased when excessive nitrogen of 320 kg·hm^-2 was applied; the proportion of globulin was decraesed gradually with the increasing nitrogen supply. 2 Effects of nitrogen fertilizer rate on GMP content and particles size distribution in wheat grainsDuring grain filling, the content of GMP in wheat grain fell first, rose afterwards and fell finally. The content of GMP increased within the nitrogen rates from 0 to 240 kg·hm^-2, while decreased when excessive nitrogen of 320 kg·hm^-2 was applied.At maturity, the diameter of GMP particles changed in the range of 0.375²56μm. Volume and surface area distribution of GMP particles exhibited the typical two population, while number distribution showed single peak curves. Nitrogen application could increase the percentages of number and volume of >10μm GMP particles, which indicating that nitrogen application could accelerate the formation of lager particles. Taishan9818, the large-spike cultivar, was more sensitive to nitrogen on GMP particles distribution compared with small-spike cultivar Shannong15.The analysis of correlation showed that the content and proportions of GMP in total protein were positively correlated with the volume of >100μm GMP particles and sensitively with the D4.3(weighted average volume). It implied that big GMP granules are high in contents of GMP.