The Grain Setting Characteristics Of Floret Development And The Study Of 6-benzylaminopurine Regulation Mechanism In Winter Wheat(triticum Aestivum L.)

In today’s wheat production,to further increase wheat yield,we should be based on the stable and suitable spikes,take the increase grain weight and grain number as a breakthrough.As grain growth is most frequently sink limited rather than source limited,so,yield in wheat is largely determined by the number of grains per m2.In this study,we took different genotypes and different spike type wheat varieties as experimental material,by setting cultivation experiments such as different N application levels,spraying fertilizer and exogenous hormones on the leaves,and analysing the relationships between cultivation measures and floret develop into grain,to make clear the regulation effects of cultivation measures on floret develop into grain.And through analysing the relationship between hormones and floret develop into grain,to make clear the regulation mechanism of exogenous hormone 6-BA on floret develop into grain.To discuss the technical approach of increase grains,in order to provide theoretical and technical reference for grain number’s increase and grain yield’s improve.The experimental results are summarized as follows: 1.The differences of floret development in different genotype wheats 1.1 The differences of floret development and grain set in different wheat cultivars of various yearsThe floret differentiation rates and the degeneration rates of the modern winter and spring wheat varieties were faster than the old varieties,but the infertility rate was lower than the old varieties.The genotypic difference also observed that the spikelet set ratio and the grain/fertile floret ratio of the modern varieties were higher than the old varieties,but the grain/floret was lower than the varieties.This clear indicated that increasing the grain number should be pay attention to the cultivation regulation at the later stage of floret development.1.2 The differences of floret development and physiological variation in different spike type wheatFrom two spike-type wheats’ floret development dynamic,we can see that the differentiation speed of two spike-type flowers present first fast then slow,and the florets’ abortion rate and degradation rate of the big spike-type Zhoumai16 were slower than the multiple spike-type Yumai49-198,and the final fertile florets number of Zhoumai16 were higher than Yumai49-198.The setting rates of spikelet、floret and fertile floret of Zhoumai16 were also higher than Yumai49-198,and the setting rate of fertile florets was significantly higher than Yumai49-198.There were small differences at the setting rates of the No1,2 floret position in two spike-type wheat,but significantly differences at the No3,4 floret position.Through analyzing the difference of assimilation allocation during floret development found that at the later period of floret development,the assimilation shifted to the spike in Zhoumai16 was more than Yumai49-198,and further to analysis the correlation between the perfect floret number and the assimilation distribution of spike and nutritive organ found that,the reason for this was no relation with the total amounts of assimilation substance distribution,but there was more relation with the assimilation substance distribution between spike and nutritive organs,especially the assimilation substance distribution in the spike.From analyzing the content change of endogenous hormones IAA,GA3,CTK and ABA during floret development stages,it showed that the higher content of IAA,GA3,CTK and the lower content of ABA in the spike were an important physiological basis to form a large spike in the later development stage.In the later development stage,the ratio of IAA/ABA,GA3/ABA and CTK/ABA of Zhoumai16 were significantly higher than Yumai49-198,especially the ratio of CTK/ABA was most significantlly.Further to analysis the relationship between perfect floret numbers and the endogenous hormone contents during floret development period,we found that the perfect floret numbers at 14d、40d after jointing were significantly and positively correlated with the content of IAA in spike,and at 14d、35d after jointing were significantly and positively correlated with the content of GA3 in spike,and at 14 d after jointing was significantly and positively correlated with the content of CTK in spike,but it was significantly and negatively correlated with the content of ABA at 14 d after jointing,and at 28 d after jointing,it were significantly and negatively correlated with the content of IAA、GA3、CTK and ABA.2.The study of cultivation regulation measures on floret develop into grain 2.1 Effect of different nitrogen application levels on floret develop into grainCompared with N0,especially the increased range of the central spikelets and apical spikelets in N180 was larger.Further to analysis,N180 can significantly promote florets grain-setting at different floret position of the different spikelets,especially promote producing seeds of the No2,3 floret position which are weak florets.Under different nitrogen levels,dry weight of main stem showed a increase trend with floret development.The stem weight of N180 treatment was significantly higher than that of N90、N0 treatments at 14 d after jointing.Along with the process of young spike development,the nitrogen content of stem showed a increased trend,and presented: N180>N90>N0,the weight of floret and the nitrogen content of floret also showed: N180>N90>N0.Along with the floret development,the total soluble sugar content of spike under different N levels showed a first went up then went down and then raise trend.And the sucrose content of spike presented first went up then went down.The total soluble sugar content of floret showed increase trend under N0 level,and showed first went up then went down trend under N90、N180 levels;the sucrose content of floret presented a first went up then went down and then raise and then went down trend.At anthesis,the distribution of assimilates in spike and nutritive organ increased with the increasing nitrogen level,and under three N levels all showed: N180>N90>N0,and under the N180 treatment it was significantly higher than that of N90,N0 treatment.The perfect floret number at anthesis、grain number at mature stage showed: N180>N90>N0 with the N level’s increase.This stated that the effects of nitrogen levels on the the distribution of assimilates、the perfect floret number and grain number was larger.The reasonable application N could help to promote the distribution of assimilates,and could promote the formation of perfect floret and develop into grain,which could establish material foundation for the formation of the grain number.2.2 The regulation effects of foliar spraying boron on floret develop into grainThe grain-setting rates of fertile floret on the basal and central spikelet positions were increased by 5.85% and 12.55% respectively compared with the control treatment which spraying water;the basal spikelet floret’s degeneration rate of spraying boron decrease by 7.47%,and the infertility rate decrease by 20.07%,the central spikelet floret’s degeneration rate of treatment decrease by 12.06% and the infertility rate decrease by 35%.The treatment can restrain the degeneration and infertility rate of the basal and central spikelet floret,but has no obvious effect on the degeneration of apical spikelet floret.Further analysis,spraying boron can significantly promote florets grain-setting at different floret position of the different spikelets,especially promote producing seeds of the No.4 floret position which is weak floret.During the anthesis period,there were no difference on stem weight,stem nitrogen accumulation and spike nitrogen accumulation between two treatments,but the spike weight,spike/stem weight,spike weight/spike nitrogen accumulation in boron treatment were significantly higher than control treatment,and on the spike weight/spike nitrogen accumulation reached an extremely significant level.The perfect floret number per unit area of spray boron increase by 16.68% compared with the control treatment which spraying water at anthesis,and the grain numbers per unit area of spray boron increase by 18.9%.At that,the reason of perfect floret number increase at anthesis and grain number increase under spraying boron treatment was related to the assimilation substance distribution between spike and nutritive organs,and was more relation with the assimilation substance distribution in spike position.2.3 The regulation mechanism of exogenous hormone 6-BA on floret develop into grainThis comprehensive study were analysed in detail floret development in wheat as affected by foliar spraying 6-BA and found that the grain-setting rates of fertile floret on the basal,central and apical spikelet positions were increased by 8.35%,15.06%,and 10.55% respectively compared with the control treatment which spraying water;the basal spikelet floret’s degeneration rate of spraying 6-BA decrease by 22.2%,and the infertility rate decrease by 72.99%,the central spikelet floret’s degeneration rate of treatment decrease by 14.7% and the infertility rate decrease by 75.98%.The treatment can restrain the degeneration and infertility rate of the basal and central spikelet floret,and also can restrain the infertility rate of the apical spikelet floret to promote producing seeds.This kind of spraying has no obvious effect on the degeneration of apical spikelet floret.Further analysis,spraying 6-BA can significantly promote florets grain-setting at different floret position of the different spikelets,especially promote producing seeds of the No3,4 floret position which are weak florets.During the anthesis period,the perfect floret number per unit area of spraying 6-BA increase by 24.97% compared with the control treatment which spraying water at anthesis,and the grain numbers per unit area of spray boron increase by 28.86%.But,there were no difference on stem weight,spike weight,stem nitrogen accumulation,spike nitrogen accumulation,spike/stem weight,spike weight/spike nitrogen accumulation between two treatments.Which state that spraying 6-BA could significantly promote perfect florets number and grain number increase,but the reason for this was no relation with the assimilation substance distribution between spike and nutritive organs.With the perfect floret development process,the expression levels of gene Ta CKX1 presented first went up then went down and then rised again.The activity of CKX presented a “M” model in water treatment,which first went down then went up and then declined and then rised again.The content of CTK presented a “V” model in two treatments during the fertile floret development stage,which first went down and then went up.At last,we found that foliar spraying 6-BA could decrease the expression of Ta CKX1 and restrain the activity of CKX during fertile floret development and disturbing the normal mechanism of cytokinin homeostasis,and to promote the synthesis and accumulation of CTK then resulting improve cytokinin level and lead to enhanced grain number of fertile floret development and grain yield.