| It has been agreed that main factor to limit wheat potential high yield were the grain number per spike and the weight per grain.According to the limited minimum factor of ecology law,the grain number of per spike had become a short board to limit the wheat grain yield.As research showed,the key to improve development and fructification of floret was promoting the yield of wheat.By contrasting conditions of different nitrogen levels(0 kg/hm2(N1)?180 kg/hm2(N2)?240 kg/hm2(N3)and 360 kg/hm2(N4))and different density levels(225×l04seedlings hm-2(W1)?450×l04seedlings hm-2(W2))with two wheat of different spike types(large-spike cultivar zhoumail6(V1)and multl-spike cultivar yumai49-198(V2))The dynamic models and characteristics of florets development and grain set characteristics were studied in the experiment station of Henan Agricultural University in 2015?2017 growing seasons.The experiment analyzed the relationship between different nitrogen levels and density.Meanwhile,the regulation mechanism of florets development was determented by different cultivation measures.The main results were as follows:1 The effect of different nitrogen levels on the characteristics of floret development and grain set of two spike-types wheat1.1 The effect of different nitrogen levels on the characteristics of floret development of two spike-types wheatResearch pointed out that wheat material production,accumulation and transportation can reach the top when the nitrogen application in 180?270 kg·hm-2 in Henan Province.There should be obvious positive correlation between accumulation of nitrogen in the plant and grain number per spike of wheat.GDD(growing-degree-day)was used to calculate the growth of plants,harvest time and quality.In this report,GDD(growing-degree-day)was an important merit to study the relationship between floret development and hit source.Experimental investigation showed that rising curing can be described the dynamic of floret differentiation between two cultivars and straight line can be described the degeneration and infertility in relation to the growing-degree-days(GDD).With the creasing of nitrogen application amount,large spike type wheat has more floret differentiation number,fertile florets differentiation number,fertile spikelet number,floret differentiation rate and degeneration rate.multi spike type wheat turns out more florets in middle nitrogen levels.It was clearly indicated that the number of florets was not the only factor to decide the grain number,more attention should be paied on the cultivation of regulation at the later stage of floret development1.2 Difference of the content of sucrose and soluble sugar of two spike-types wheat under different nitrogen levelsAnalyzing the content of sucrose and soluble sugar in stems and leaves,we can find that The stems and leaves acted as storage organs in the early stage and the storage organs played as the transportation when the florets and spikelets get into the rapid developing stage.Soluble sugar in stems was continuously increasing from the JS to AS,while sucrose was decreasing at begining and then increasing.The soluble sugar in the stem is a continuously decreasing process from the JS to 5d post-AS,but The change of sucrose was continuously fluctuating within a range.1.3 Difference of dry matter and nitrogen accumulation of two spike-types wheat under different nitrogen levelsResults showed that from WS to MS,dry matter and nitrogen accumulation in wheat were gradually increasing,and two cultivars in dry matter and N accumulation are in obvious differences after jointed,Between JS and AS,the contribution rate of post-anthesis assimilated dry matter to grain yield was a major determinant of wheat grain yield,and they were the biggest when the nitrogen levels were reasonable.At the same nitrogen level,the contribution rate of post-anthesis assimilated dry matter to grain yield of zhoumail6 was higher than yumai 49-198.Reasonable application of nitrogen fertilizer was also beneficial to the accumulation and transportation of the aboveground nitrogen in wheat and is the foundation for getting high yield.Through further analysis of three factors make up the grain yield on two spike type wheat,it conducted that a balanced amount of nitrogen can coordinate the relationship between the three factors.High and low nitrogen levels breaked the balance between the three factors and caused the decline in grain yield.2 The effect of different density levels on the characteristics of floret development and grain set of two spike-types wheat2.1 The effect of different density levels on the characteristics of floret development of two spike-types wheatThe result showed that total florets,fertile florets,grains total florets set,fertile florets set and spikelets set of W1 treatment were more than W2 treatment of two spike-type wheat.Among them the fertile florets sets of V1W1 treatment was 55.29%higher than that of V1W2,and the fertile florets sets of V2W1 was 50.39%was higher than that of V2W2.The higher density levels increased the nutrition competition among the plants,which directly influent the development of florets and the formation of yield.While high planting density made a decrease of spikelet number in different parts of the spikelet,The grain weight in different parts of spikelet was also decreased for large spike-type wheat.There was no obvious change of grain weight in the middle and top parts for multi spike-types wheat yumai49-198.2.2 The effect of different density levels on the dry matter and nitrogen accumulation of two spike-types wheatFrom the date of accumulation and transportation of dry matter and nitrogen in the ground,it conducted that suitable planting density enables wheat to make full use of nutrients and light conditions,by increasing dry matter quality and coordinating nutrient elements transportation and distribution among organs.However,excessive planting density not only leads to waste of resources,but also restricts the accumulation and transport of some dry matter and nitrogen in the ground.Thus,the destruction of the balance of the three factors of grain yield causes the decrease of the yield per unit area.3 Difference of the content of endogenous hormone(CTK,IAA)in different organs of two spike-types wheatFrom analyzing changes of the content of endogenous hormone CTK and IAA in leaves and spikes from jointing past,it showed that the contents of CTK in leaves and spikes of multl-spike cultivar were generally higher than that of large-spike cultivar.The content of IAA of large-spike cultivar was higher than that in the early stage,but it was lower than that latter.It was indicated that there were differences in the contents of endogenous hormones of different spike types wheat in different organs.The contents of CTK and IAA in the leaves and spikes of large-spike cultivar get to the top when the degeneration and infertility of florets achieved their peak.However the degradation and abortion rate of the arge-spike cultivar higher than that.It showed that the degradation and abortion of florets were related to the content of endogenous hormones in wheat. |
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