| The toxic effect of heavy metal cadmium(Cd)in soil will inhibit the growth of plants,and application of selenium(Se)can alleviate the stress of Cd on plants.There have been many studies on the effects of Se-Cd interaction on the uptake and translocation of Se and Cd in plants,but the difference and mechanism of detoxification of Cd by different species and concentration of exogenous Se are still unclear.Most of the existing studies mostly take the soil with exogenous Cd as the research object,and seldom explore the influence of exogenous Se application on natural Cd-contaminated soil.Therefore,in this study,natural Cdcontaminated soil and pak choi were selected as experiment materials to study the effects of different exogenous Se on growth and Se and Cd uptake of pak choi,and to explore the effects of exogenous Se application on Se and Cd fraction transformation and bioavailability in Cdcontaminated soil,so as to provide scientific basis for Se enrichment and Cd reduction in actual production.The results are as follows:1.Exogenous Se application can reduce Cd uptake of pak choi,but different exogenous Se has different effects on Cd uptake of pak choi.Whether growing for 35 days or 70 days,the Cd concentration in the shoot of pak choi increases first and then decreases with the amount of Se application.Among them,basal application of 0.5 mg/kg selenite has the greatest inhibitory effect on Cd,while basal application of 1 mg/kg selenite has the most significant inhibitory effect on Cd.On the whole,selenite at 1 mg/kg can reduce the accumulation of Cd in the shoot of pak choi,and it plays the most significant role in the later growth stage of pak choi.The application of exogenous Se can increase the Se concentration in different parts of pak choi,and different concentrations and different species of exogenous Se have different effects on Se uptake of pakchoi at different growth stages.With the extension of growth time,the Se concentration in the aboveground and underground parts of pak choi treated with selenite for 70 days was not significantly different from that of pak choi grown for 35 days.However,Se concentration in the aboveground and underground parts of pak choi treated with selenate decreased with the extension of growth time.2.The addition of exogenous Se can alleviate the stress of soil Cd on the growth of pak choi,and the effect of the same exogenous Se on the growth of pak choi has nothing to do with the growth period of pak choi.The plant height,shoot biomass and root biomass of pak choi treated with selenite were significantly higher than those without selenium treatment,and the SPAD value,Pn,Gs,Ci,biomass and shoot height of pak choi treated with selenite at low concentration(≤ 1 mg/kg)were significantly higher than those without selenium treatment.For selenate treatment,low concentration(≤ 1 mg/kg)promoted the growth of pak choi,but high concentration(2.5 mg/kg)had toxic effect on the growth of pak choi,which showed that its shoot height,shoot and root biomass,Pn,Gs were significantly lower than those of the control without selenium application.3.Under the condition of Cd pollution,Se application affected the existing fraction of Cd in soil.The ratio of ECH-Cd to total Cd in soil was significantly lower than that without Se application,and the ratio of CAB-Cd to total Cd increased significantly,which led to the decrease of the availability of Cd in soil,thus reducing the absorption of Cd by pak choi.Se in selenite treatment mainly exists in EX-Se and FMO-Se,while selenite treatment soil mainly exists in SOL-Se.With the extension of growth time of pak choi,the content of available Se in selenite treatment soil gradually increased,while the residual Se gradually decreased with the extension of growth time.However,the ratio of SOL-Se to total selenium in selenate treatment soil decreased significantly with the extension of growth time,while the ratio of EXSe to total selenium increased significantly.Therefore,the application of exogenous Se can affect the speciation transformation of Se and Cd in soil,and reduce the uptake of Cd by pak choi.The detoxification effect of low concentration(≤ 1 mg/kg)Se on Cd is more significant than that of selenate,and there is synergistic stress between high concentration(2.5 mg/kg)Se and Cd in soil.Therefore,comprehensive consideration should be given to the application types and valence states of Se,so as to realize the safe utilization of Cd-contaminated soil and achieve the purpose of enriching Se and reducing Cd in plants. |
PDF Full Text Request