Effects Of Nitrogen Level On Yield Formation And Assimilate Operation Of Different Dominant Maize Varieties

The efficient grain-filling is one of the most important characteristics of maize with high yield and high efficiency,and the different genotypes maize have significant differences in efficiency of grain filling.In order to identify the relationship between the grain filling characteristics and the difference of dry matter translocation and grain yield with different genotypes maize,the different heterotic pattern varieties Zhengdan 958,Zhongdan909,Weike702(ZD958 type varieties,mode of ReidxTang four flat)and XianYu335,Nonghua 101,Jingke 968(XY335 type varieties,mode of Reidx Lancaster)as test materials in this paper,3 levels of Nitrogen fertilizer application(0kg/ha(N0),100 kg/hm~2(N1)and 300 kg/hm~2(N3))and two planting densities(D1(67500 plant/ha)and D2(90000 plant/hm~2))were established,take the method of 13C isotope labeling and microscopic observation to investigate grain filling characteristics,the vascular bundle structure,the relationship between dry matter translocation and grain yield on two type varieties.The main results as follows:The grain yield of XY335 type varieties were higher than those of ZD958 type varieties with the suitable nitrogen fertilizer under two kinds of density.The yield of XY335 type varieties yield were higher than those of 0.17%and 5%under normal(67500 plant/hm~2)and high density(90000 plant/hm~2)conditions,respectively,XY335 type varieties mainly by increasing grain number and increase yield,and ZD958 type varieties mainly through increased 1000 grain weight increase yield.XY335 type varieties increase yield mainly by increasing grain number,and ZD958 type varieties mainly through increased 1000 grain weight of nitrogen application in two type varieties,and the increase of grain number per panicle of XY335 type varieties higher than those of ZD958 type varieties,on the contrary the 1000 grain weight were greater than XY335 type varieties.The grain yield of XY335 type varieties and ZD958 type varieties were not significant under normal density and suitable nitrogen fertilizer(300 kg/hm~2)while the yield of XY335 type varieties were significantly higher than those of ZD958 type varieties under high density condition.XY335 type varieties were sensitive to nitrogen fertilizer response in filling process,and ZD958 type varieties were more sensitive to density.The average grain filling rate and maximum grain filling rate of XY335 type varieties were significantly higher than those of ZD958 type varieties,but the filling duration was significantly shorter than that of ZD958 type varieties.XY335 type varieties filling duration were increase with the density increased as well as ZD958 type varieties decreased.The grain filling duration of XY335 type varieties in high density and high nitrogen fertilizer increased 12%than the normal density,however ZD958 type varieties decreased 6%under suitable nitrogen fertilizer.The peak of grain filling of XY335 type varieties was 3-5 days earlier than that of ZD958 type varieties,and XY335 varieties after the peak of grain growth rate was significantly lower than those of ZD958 type varieties with the normal density.XY335 type varieties had better vascular structure characteristics,which can effectively promote the dry matter translocation and increased grain filling rate.Compare with ZD958 type varieties,the basal stems of each treatment in XY335 type varieties had greater the large and small vascular bundle area,the vascular bundle phloem area,the vascular density.The number of peduncle vascular bundles of XY335 type varieties were less than ZD958 type varieties with two the density of zero nitrogen and low nitrogen conditions.XY335 type varieties of vascular bundle xylem and phloem area were larger than those of ZD958 type varieties,respectively increased 9.2%and 0.6%under suitable nitrogen and density condition,while the results were opposite under the high density condition that respectively decreased 54%and 32%.XY335 type varietie.The ear-located large and small vascular bundles area were higher tharn that of ZD958 type varieties.XY335 type varieties density of ear-located vascular bundle were significantly lower than ZD958 type varieties under suitable nitrogen fertilizer and two density,while under the condition of suitable density and high density XY335 type varieties in vascular bundles were increased 29%than ZD958 type varieties.The sum of large vascular bundle area,vascular bundle xylem area in ZD958 type varieties which were larger than XY335 type varieties at the two density,and the results were opposite at small vascular bundle xylem area,phloem area and the total area of them.The dry matter accumulation of XY335 type varieties were higher than that of ZD958 type varieties,but there were no significant difference in the contribution rate of dry matter accumulation after anthesis with the different type varieties.The 13C labeling showed that the proportion of 13C assimilates distribution to stem and grain were significantly higher than that of ZD958 type varieties at grain filling stage under suitable nitrogen fertilizer.There were no significant differences in carbon distribution between stem and seed beween the two types varieties under high density and suitable nitrogen fertilizer,and the carbon distribution significantly higher than other organs at maturity stage.The difference in carbon distribution of the grain beween XY335 and ZD958 type varieties were reduced by 9%and 23%with suitable Nitrogen fertilizer under high density and suitable density.In a word,on condition of high density with normal fertilizer,the grain yield of XY335 type varieties were significantly higher than thoes of ZD958 type varieties,and the reason that were the relative improvement of the structure and function of vascular bundles,promote photosynthate and nutrients transport becomes fluency,meanwhile improving the filling material efficiency,reaching the maximum grain filling time was significantly reduced,and improve grain filling rate and increase grain yield of maize.