Mechanism Of Alleviation Effects Of Exogenous Strigolactones On Drought Stress In Wheat

As the main food crop,wheat is very sensitive to drought,salinity and heavy metals and so on.Drought has become one of the most important limiting factors of wheat yield and quality.Our previous study showed that Strigolactone had a mitigating effect on drought stress of wheat seedlings.In order to better explore the alleviating effect of SLs on drought stress in wheat seedling stage,a hydroponic experiment with Bai Nong 207 was carried out.Double-leaf-period wheat seedlings were watered with 0.8 μM rac-GR24,a synthesized strigolactone,and then were subjected to 20%(w/v)polyethylene glycol(PEG-6000)to simulate the drought conditions.The main research results are as follows:1.GR24 could effectively alleviate the inhibition of drought stress on growth of wheat seedlings.Compared with drought stress,SLs treatment effectively increased the aboveground dry matter by 40.94%,and the underground dry matter increased by 26.21%.The relative water content and total chlorophyll content of leaves were significantly increased by 12.18% and 23.58%,Fv/Fm and Fv/Fo of PS II were increased by 7.95% and 20.14%,respectively.The activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)increased by 14.79%,6.18% and 12.63%,respectively.The contents of glutathione(GSH)increased by 43.90% and the ratios of GSH/GSSG increased either.The levels of reactive oxygen species decreased significantly,the hydrogen(H2O2)content and malondialdehyde(MDA)content decreased by 26.29% and 31.59%,respectively,and GR24 effectively alleviated membrane damage caused by drought stress.Moreover,proline and soluble sugar content decreased by 29.41% and 29.44%,respectively.2.The expression level of Ta CCD7,the SLs biosynthetic gene,was significantly up-regulated in wheat roots and leaves after treatment with SLs.At 72 h,the expression levels were up-regulated by 62.39% and 45.25% in roots and leaves,respectively.The expression levels of signal transduction genes Ta D14,Ta MAX2 and Ta D53 in leaves were up-regulated by 157.19%,144.05% and 187.78%,respectively,and the expression levels of Ta D14,Ta MAX2 and Ta D53 in roots were significantly up-regulated by 18.38%,23.47% and 12.32%,respectively.The expression level of Ta NCED1,the ABA synthesis gene,was significantly up-regulated,while Ta HYD1,the ABA decomposition gene,was significantly down-regulated after treatment with SLs,which was beneficial to the accumulation of abscisic acid.Meanwhile,the expression of the ABA signal transduction gene Ta Sn RK2.3 was significantly up-regulated.As a result,SLs could increase the chlorophyll content and photosynthetic efficiency under drought stress,promote dry matter accumulation,reduce the osmotic regulation substances content,enhance the antioxidant capacity,promoted the SLs synthesis and signal transduction and ABA accumulation.SLs promoted the growth of wheat seedlings,effectively improved the drought resistance of wheat seedlings.