Genotypic Differences Of Wheat In Response To Selenium, Lead And Cadmium Stress

Lead(Pb)and cadmium(Cd)are widely distributed in natural soils and cause serious harms to human health.In recent years,due to industrial wastewater and exhaust emissions,some of the soil in the world has been seriously polluted by Pb and Cd.Pb and Cd can be consumed by wheat,and then taken into the human body through the food chain,which poses a potential risk to human health.Selenium(Se)is a beneficial nutrient element in plants,which can antagonize the absorption of heavy metals and detoxification of wheat.However,the genotypic difference and mechanism of heavy metals influenced by Se in wheat are not yet clear.In this experiment,hydroponic screening method and soil culture were employed to understand the effect of Se on Pb and Cd in wheat(resistance and sensitive varieties).The research is of great significance in understanding the role and mechanisms of amendments in controlling soil heavy metal pollution and guiding the application of amendments in agricultural land.The main results were summarized as follows:1.The effects of Se,Pb,and Cd treatments on the growth,enzyme system,Se,Pb and Cd contents of 14 wheat varieties(P01-P14)were studied by hydroponics.The results showed that the growth of wheat was significantly inhibited by Pb(300mg/L)and Cd(0.5mg/L)treatment.Most of the Se,Pb and Cd absorbed by wheat were accumulated in the roots.Based on the dry weight ratio of treatments(Se,Pb and Cd)to Control of 14 wheat varieties,two sensitive varieties(P01 and P13)and two resistant varieties(P06 and P09)were selected for future studying.2.A soil culture experiment was employed to study the effects of Se,Pb and Cd on the growth and antioxidant system of selected resistant varieties(P06,P09)and sensitive varieties(P01,P13).The results showed that the Se treatments decreased the inhibitory effect on wheat growth by Pb and Cd,which the varieties ranked as P09 > P06 > P13 > P01.The resistance of P06 to lead is better than that of P09,and P09 to cadmium is better than P06.The relative biomass of Se,Pb,and Cd treated wheat was positively correlated with SOD,POD,CAT,GSH-Px activity,protein and GSH contents under each treatment.The relative biomass of Pb and Cd had a significant negative correlation with MDA content.The antioxidant system could better reflect the growth status of different wheat varieties and their tolerance to Se,Pb,and Cd.3.Determination of the contents of Se,Pb,Cd,N,P,K,and the grain quality of the 4 typical wheat varieties at different growth stages showed that the contents of Se,Pb and Cd in different wheat varieties were 2.67-3.46,3.92-5.26 and 2.90-6.79 mg/kg respectively,and the difference between varieties was significant(P < 0.05).The treatment of Pb and Cd effectively increased the absorption of N and P,but inhibited the absorption of K,while the Se treatment effectively promoted the uptake of N and P.The content of N,P,and K and the content of Se,Pb and Cd were well synergistic in different growth stages.It further verified the promotion effect of Se on the absorption of N,P and K and the promotion effect of Pb and Cd on N and P,and the inhibition of K.4.The effects of exogenous supply of Se on MDA content and GSH-Px activity in different wheat varieties during grain filling stage were studied.The results showed that the exogenous Se significantly increased the GSH-Px activity under Pb and Cd stress,significantly reduced the MDA content,suggesting that Se alleviated the toxicity of Pb and Cd to wheat,promoted the growth of wheat,and improved the wheat biomass,grain yield and quality.5.Foliar application of Se promoted the wheat absorption of Se,inhibited the absorption of Pb and Cd,and effectively reduced the content of Pb and Cd in wheat stems,leaves and grains.The average decrease of Cd content in 4 varieties was 18%,and the average decrease of Pb content was 18%,and all of them were the highest in P06 varieties.Exogenous Se increased the Se content of wheat 0.84-1.31mg/kg,which was 3.5-9.0 times higher than that control.6.The responses of growth and yield traits of 4 different varieties to Se,Pb,and Cd were studied.The results showed that under the treatment of Se,Pb,and Cd,the content of Se in the stems and leaves of P06 varieties was higher,the content of Cd was lower,and the accumulation of Se,Pb and Cd were higher than those of the other varieties.After exogenous application Se,the yield and 1000 grain weight of the 4 wheat varieties were highest in P06.And the Pb and Cd decreased at different growth stages and in different parts,such as,the content of Pb and Cd in flour deceased by 28% and 49% respectively.These results suggested that planting P06 with exogenous selenium could effectively reduce Pb and Cd enrichment in grain and increase wheat yield and quality.