Alleviating Effects Of Exogenous Selenium On Nutrient Accumulation And Salt Stress In Durum Wheat

In this study,the extreme high and low selenium(Se)conentration lines from a Triticum dicoccoides × Triticum durum recombinant inbred lines(RILs)mapping population(durum wheat R6,R113,R126,R128,R171)were selected and hydroponic experiments were conducted to study the effects of different concentrations(0,0.1,1,2,4,8,10 ?M)of sodium selenate(Na2Se O4)and sodium selenite(Na2Se O3)on durum wheat seed germination and seedling growth under salt stress(50 m M Na Cl).Our results provided a scientific basis for exploring the mechanism of Se in alleviating the salt toxicity of wheat.On this basis,the effects of soil Se application(0,5,10 mg kg-1)and foliar Se application(0,11.5,23 mg L-1)on growth,yield and quality as well as absorption and transport of trace elements in sink-source organs(flag leaves,husks and grains)of durum wheat(R113,R171)with different Se tolerance were studied with Na2 Se O4 as exogenous Se via soil experiments,which provided theoretical basis for conducting Se biofortification of wheat.The main results were as follows:1.Application of exogenous Se in the salt solution attenuated the salt stress effects on seed germination and seedling growth of durum wheat in form and concentration-dependent manners of Se.Low concentrations(0.1-4 ?M)of Na2 Se O4 or Na2 Se O3 addition showed significant alleviation of salt stress on germination rate,germination energy and germination index as well as promoted seedling growth.Meanwhile,Na2 Se O4 was more effective than the same concentration of Na2 Se O3.However,high concentrations(8-10 ?M)of Na2 Se O4 or Na2 Se O3 can also cause damages to seed germination and seedling growth,and the damages caused by Na2 Se O3 was more severe than Na2 Se O4.2.Addition of low concentrations exogenous Se can decrease the conentrations of free proline,malondialdehyde(MDA)and electrolyte leakage,increase catalase(CAT),superoxide dismutase(SOD)and peroxidase(POD)activities in the roots and shoots,slow the decline rate of non-photochemical fluorescence quenching(NPQ)and minimal fluorescence(Fo),promote the rise of photochemical quantum yield [Y(II)],maximal fluorescence(Fm),maximal photochemical efficiency of photosystem II(Fv/Fm),variable fluorescence(Fv)and potential efficiency of photosystem II(Fv/Fo)in leaves of seedling.Therefore,the exogenous Se can improve the adaptability of processing durum wheat to salt stress and maintain higher photosynthetic rate by decreasing the accumulation of reactive oxygen species(ROS)and alleviating the degree of membrane lipid peroxidation.3.Both foliar Se and soil Se application methods significantly increased Se conentrations in sink-source organs of durum wheat,but most of the Se(more than 50%)was accumulated in flag leaves and husks,while lower amounts in grains.The effect of Se addition on proportions of Se in sink-source organs was both application methods and conentration-dependent manners of Se.Se conentrations in sink-source organs increased as Se application rates increased.For Se applied to the soil,flag leaves and husks accumulated high amounts of Se at the expense of grains.Foliar Se application resulted in a greater proportion of Se in grains compared with soil Se application.4.Both methods of Se application promoted the absorption and accumulation of trace elements(Fe,Zn,Cu,Mo),secondary metabolites and nitrogen nutrients in the sink-source organs,and the promotion effect of foliar Se application was higher than that of soil Se application.However,addition of high concentrations exogenous Se(23 mg L-1,10 mg kg-1)caused their absorption and accumulation to decrease.In addition,two Se application methods decreased potentially toxic trace elements(Pb,Al,As,Li and Cd)conentrations in all sink-source organs,indicating a possible antagonistic effect.Accordingly,this study provided useful information concerning agronomic biofortification of wheat,showing that it is feasible to apply Se in fertilization programmes(0-5 mg kg-1 or 0-11.5 mg L-1)to improve yield and quality in crops.And the foliar Se application was better than soil.