Effects Of Nitrogen Fertilizer Topdressing Stage On Yield And GMP Accumulation In Wheat

In this study, we used a strong gluten winter wheat cultivar, Jinan17, and a weak glutenwinter wheat cultivar, Lumai21, to investigate the effects of nitrogen topdressing stage onkernel yield, the accumulation of HMW-GS and the size distribution of GMP in grains. Thenitrogen fertilizer rate during the whole growth period was225kg ha1, of which a half wasapplied as base fertilizer and the other half was topdressed at pseudo stem erection (SE, GS30), jointing (JT, GS32), or booting (BT, GS41) stage. The experimentation was carried outin the experimental farm of Shandong agricultural university from2009to2012.The mainresults read as follows:1Effects of nitrogen fertilizer timing on nitrogen metabolism of wheatNitrogen topdressing at jointing stage not only increased the accumulation nitrogen offlowering period, also be helpful for nitrogen translocation from vegetative organs to kernel.Nitrogen translocation efficiency of all vegetative organs has high correlation with cultivationmeasures and genotype difference, Jinan17performance for JT> BT> SE, Lumai21performance for SE> BT> JT, and Jinan17had higher the average nitrogen translocationefficiency than Lumai21. The contribution proportion of nitrogen from vegetative organs tokernel showed greatly difference in different cultivars and treatment. For cultivar Jinan17,nitrogen topdressing at pseudo stem erection stage increased the contribution proportion, butfor cultivar Lumai21, the contribution proportion improved at booting stage.2Effects of nitrogen fertilizer timing on the contents of protein and protein componentsThe changes of protein content of the both cultivars in the grain filling process weresomething like the curve of high, low and then going up. At maturity, the content of protein in Jinan17showed decreasing trends with the delay of topdressing practice, and in Lumai21the highest values was observed in the JT treatment. With the postpone of nitrogenapplication, the contents of albumin and gluadin increased in wheat, while the content ofglobulin decreased. Jinan17had higher contents of gluadin than Lumai21, and the content ofgluten was seldom affected by nitrogen application timing in kernel of Jinan17and Lumai21.3Effects of nitrogen fertilizer timing on yield of wheatThe two cultivars, Jinan17and Lumai21, showed the highest yield when nitrogen wastopdressed at jointing stage. Compared with nitrogen topdressing at pseudo stem erectionstage and booting stage, nitrogen topdressing at jointing stage made Jinan17got higher yieldbecause that increased the kernel number per spike and the weight per1000kernels. Lumai21got higher grain yield because of increasing the kernel number per spike.4Effects of nitrogen fertilizer timing on HMW-GS accumulation and GMP size distributionin wheat grainsThe HMW-GS in grains formed before14after anthesis, and Jinan17had highercontents of HMW-GS and GMP than Lumai21, which indicated that more glutenin isaccumulated in the strong gluten cultivar than in the weak gluten cultivar. At maturity, thecontents of HMW-GS and GMP in Jinan17showed decreasing trends with the delay oftopdressing practice, and the highest values were observed in the SE treatment. In Lumai21,compared to the SE and BT treatments, the JT treatment significantly accelerated theHMW-GS accumulation at middle-late stage of grain filling, and the rapid accumulationperiod was prolonged. At middle-late stage of grain filling, the accumulation rates of x-typesubunits (1,4,5, and7) were increased significantly in the SE treatment of Jinan17and theJT treatment of Lumai21, whereas the y-type subunits were seldom affected by nitrogenapplication timing.For both cultivars, delay of nitrogen topdressing enhanced the percentages of volumeand surface of GMP particle with diameter less than12μm, but reduced those of GMPparticle with diameter larger than100μm. The percentage of GMP particle number with diameter larger than12μm was increased in Jinan17with the delay of nitrogen topdressingbut decreased in Lumai21. The percentage of large GMP particle volume was higher in Jinan17(containing subunit pair4+12) than in Lumai21(containing subunit pair5+10). Thisresult suggested that polymerization of subunits and GMP particles are related to not only thesubunit type but also the subunit content per unit of flour.