Response Of Cadmium And Chelating Agents On Physiological Mechanism Of Cadmium Uptake In Poplar

Cadmium is one of the most toxic heavy metals,and is listed as the top five toxicant(Cd、Hg、As、Cr、Pb).Industrial "three wastes" emission and unreasonable agricultural management measures are the main causes of soil cadmium pollution.In view of the existing remediation technologies of heavy metal contaminated soil,the physical and chemical remediation methods,such as soil replacement or leaching,are difficult to be applied for technical,economic or social reasons.Using plants to repair cadmium contaminated soil,the key is to find plants with strong accumulation ability,and study the mechanism of absorption and accumulation of cadmium,it was improve and cultivate new cadmium accumulated plants on this basis.Compared with herbaceous plants,woody poplar trees are characterized by rapid growth,well-developed roots and large biomass.In this study,the poplar was used as the research object.Analyze the effects of adding different chelating agents(1 mg/kg EDTA+Cd,5 mg/kg EDTA+Cd,1 mg/kg EGTA+Cd,5 mg/kg EGTA+Cd,1 mg/kg EDTA+1 mg/kg EGTA+Cd and 5 mg/kg EDTA+5 mg/kg EGTA+Cd)on the fluorescence,chlorophyll,carotenoidand antioxidant enzyme activity,and the roots,bark and leaves biomass,antioxidant enzyme defense system,superoxide anion,malondialdehyde,proline,soluble protein content and transport coefficient,tolerance index,enrichment factor,cadmium content and mineral element content of poplar.It was provides a theoretical basis for phytoremediation of cadmium contaminated soil for chelating agents.The main conclusions are as follows:1.The effect of chelating agent induced cadmium stress on photosynthetic pigments of poplar leaves was investigated:After 1 d,the combination of EDTA+Cd,EGTA+Cd and EDTA+EGTA+Cd is compared with Cd single treatment,the contents of chlorophyll a,chlorophyll and carotenoids were increased,while the content of chlorophyll b was decreased under 1 mg/kg EGTA+Cd treatment.After 30 d,the contents of chlorophyll a,chlorophyll b,chlorophyll and carotenoids were increased with the combination of EDTA+Cd and EDTA+EGTA+Cd,Chlorophyll fluorescence Fo,Fv and Fm values were increased,it was indicated that chelating agents promoted the increase of photosynthetic pigment content in poplar leaves.2.The effect of chelating agent induced cadmium stress on biomass accumulation of poplar was elucidated:After 1 d,The combination of EDTA+Cd,EGTA+Cd and EDTA+EGTA+Cd is compared with Cd single treatment,the root was increased significantly,the leaves was increased significantly under the combined treatment of EDTA+Cd,the bark was increased with the combination of 1 mg/kg EDTA+Cd and 5 mg/kg EDTA+Cd and 5 mg/kg EGTA+Cd.After 30 d,the roots was increased with the combination of 1 mg/kg EDTA+Cd,5 mg/kg EDTA+Cd and 5 mg/kg EGTA+Cd,the bark and leaves increased with the combination of 1 mg/kg EDTA+Cd,5 mg/kg EDTA+Cd,1 mg/kg EGTA+Cd,5 mg/kg EGTA+Cd,It can be concluded that EDTA and EGTA have some promoting effects on poplar growth.3.The effects of chelating agent induced cadmium stress on antioxidant enzyme activities and osmotic adjustment substances in poplar were studied:The combination of EDTA+Cd,EGTA+Cd and EDTA+EGTA+Cd was compared with Cd single treatment,The activities of antioxidant enzymes(SOD,CAT,POD and APX)were increased,meanwhile,the contents of proline and soluble protein in different organs of poplar were increased,while the contents of MDA and O2·-were decreased.It was indicated that chelating agent with suitable concentration can effectively alleviate the toxicity of cadmium to poplar.4.It is revealed that poplar was promoted absorption,transport and accumulation ability and tolerance to Cd:The combination of EDTA+Cd,EGTA+Cd and EDTA+EGTA+Cd was compared with single Cd treatment.The cadmium content of different organs of poplarwere increased with different chelating agents treatment.It was indicates that chelating agent can promote the absorption and transportation of cadmium by poplar.