| The experiment was carried out in the dry season of the rain cover in the Tai’ an Agricultural Experimental Site of Shandong Agricultural University in the wheat growing season of 2017-2018.Winter wheat(Taikemai 33)was sown in the filed under normal irrigation(75%-80% of the field moisture capacity)and water deficit(75%-80% of the field moisture capacity).Water was controlled from floret primordium present to anthesis and Spd was sprayed to the whole leaf for three days.Treatments were spraying water under normal irrigation conditions(WW+CK),Spraying Spd under normal irrigation conditions(WW+Spd),spraying water under water deficit conditions(WD+CK),spraying Spd under water deficit conditions(WD+Spd),respectively.The components of winter wheat yield and yield,dynamics of floret development,grain setting characteristic,endogenous hormones content,soluble sugar content,sucrose content were analysised under water deficit conditions by spraying exogenous Spd.The mechanism of exogenous Spd regulating development and degradation of winter wheat florets was studied under water deficit condition,in order to providing a theoretical basis for controlling the grain number of wheat spikes by exogenous chemical control measure.The main results were shown as follow: 1.Effects of Spd on the developmental dynamic of winter wheat florets(1-4)under different water conditionUnder the normal irrigation treatment,the florets at the base,middle and top of the wheat,and the three small flowers in the middle of the ear could all develop to the W10 period.Under WD+CK treatment,wheat spike top and base 3 florets,middle and basal 4 florets could not develop to W10 stage.The base of the ear and the top 3 small flowers could develop normally after spraying Spd.WW+Spd treatment had no significant effect on the development of 1 and 2 florets in different ears and 3 florets in the middle of the ear.However,spraying Spd increased the development of the three florets at the top of the ear.The basal part of the ear and the florets of the middle part stopped developing during the W6.3 and W7.3 periods Under the WD+CK treatment.The basal and central florets of WD+Spd treatment were able to develop normally,indicating that exogenous spraying of Spd could alleviate the effect of water deficit on florets development.Spraying Spd under water deficit condition had no significant effect on the development of florets in different ear positions 1,2 florets and middle ears.However,it had significant effects on the development process of the basal part of the ear,the top 3 florets,the base of the ear,and the 4 florets in the middle.2.Effects of Spd on the floret setting characteristics of winter wheat with different ear positions under different water treatments.There were no significant differences in the number of grains between WW+CK,WW+Spd and WD+Spd except for the four spikelets at the base.Except for the first spikelet,the number of grains of WD+CK treatment was significantly lower than other treatments.Under WD+CK treatment,the number of grains in the 1,2,and 3 flower positions decreased by 4.6%,4.6%,and 5.6%,respectively,and the 4th florets could not set grain by WD+CK treatment.The number of grains in the 1,2,3,and 4 flower positions increased by 4.6%,9.1%,21.8%,57.1% and 0.7%,1.4%,4.1%,31.5% by WW+Spd and WD+Spd treatment,respectively.The average number of fertile florets in different spikelets was the highest in the middle,30-35,followed by the basal spikelets,11-16,and the lowest at the top,11-13.WW+Spd treatment could significantly increase the number of fertile flowers in the basal spikelets.WD+Spd treatment could significantly increase the number of fertile florets at the base,middle,and top spikelets.WW+Spd and WD+Spd treatments had no significant difference in the number of fertile florets in the middle spikelets and top spikelets.The number of fertile florets treated by WD+CK treatment was significantly reduced,and the basal spikelets,middle spikelets and top spikelets decreased by 11.94%,5.62%,and 9.52%,respectively.The number of grains and grain setting showed a similar trend with the number of fertile florets.3.Effect of Spd on endogenous hormone in floret under water deficitThe content of endogenous zeatin + zeatin nucleoside(Z+ZR)in the treated florets increased firstly and then decreased.There was no significant change in the content of endogenous Z+ZR in the treatments from 10 to 18 days before flowering,and there was no significant change in the content of strong florets and weak florets.The endogenous Z+ZR content increased sharply from the 10 days before flowering,and reached the maximum on the 2nd day before flowering.Under normal irrigation condition,spraying Spd could increase the Z+ZR content of weak florets,but spraying Spd could not increase the Z+ZR content of strong florets.Spraying Spd could increase the Z+ZR content in strong and weak florets under water deficit condition.At 18 days before flowering,the changes in endogenous ABA content of strong florets and weak florets were significantly different.The endogenous abscisic acid(ABA)content of strong florets increased firstly and then increased during this period,and reached the minimum on the 6th day before flowering.Under water deficit treatment,the ABA content in strong and weak florets was significantly higher than other treatments.From the 2 days before flowering,the weak florets treated by WD+Spd significantly reduced ABA content by 28.12% and 13.96%,respectively.The content of endogenous spermidine(Spd),spermine(Spm)and putrescine(Put)in wheat florets from the 14 days before flowering showed a significant downward trend.The content of Spd and Spm in the strong florets of wheat was significantly higher than that of the weak florets,while the Put content in the weak florets was slightly higher than that of the strong florets.WW+Spd and WD+Spd treatments increased Spd and Spm content in floret and reduced Put content.The application of exogenous Spd in water deficit conditions improves the content of Spd,Spm and Z+ZR in the florets,and increased the ratio of weak florets(Z+ZR)/ABA,and reduced the Put content.On the one hand,it accelerated the development of weak florets and inhibited the degradation of florets,On the other hand,the number of fertile florets was increased,and the number of grains at different spikelets was increased,thereby increasing the grain setting rate.Therefore,under the condition of water deficit,the application of exogenous Spd during the development of florets could increase the grain number of wheat and increase the grain yield of wheat.4.Effect of Spd on yield and yield components of winter wheat under water deficitThe number of kernels and yield of WW+CK treatment were significantly higher than that of WD+CK treatment.Spraying exogenous Spd significantly increased wheat grain yield,and WW+Spd and WD+Spd treated grain yield increased by 2.01% and 20.83%,respectively.Because the application of exogenous Spd significantly increased the number of kernels in the yield component.Under WW+Spd and WD+Spd treatment the number of kernels increased by 11.87% and 13.75%,respectively.However,the application of exogenous Spd had no significant effect on the number of ears per unit area and 1000-grain weight. |
