不同镉浓度下绿穗苋根际环境特征与镉形态分布

为了解镉(Cd)富集植物根际环境对镉的活化和耐受作用,通过土壤盆栽试验,研究了Cd胁迫下绿穗苋根际环境特征变化和镉形态分布。研究表明:绿穗苋根际pH低于非根际,并随Cd浓度升高总体呈下降趋势;根据DOC含量高于非根际,且随着Cd浓度的增加呈逐渐上升趋势。随着Cd浓度的升高,绿穗苋根际土壤交换态Cd所占比例上升,铁锰氧化物结合态Cd所占比例先升高后降低,碳酸盐结合态Cd、有机结合态Cd和残渣态Cd所占比例均逐渐降低。各处理根际土壤过氧化氢酶、脲酶和磷酸酶活性均高于非根际,根际土壤脲酶和磷酸酶活性均随处理浓度升高呈先升高后降低的趋势,过氧化氢酶活性随处理浓度升高持续下降。结果表明,Cd胁迫下绿穗苋根际pH和DOC的变化对Cd活化具有重要作用,根际土壤酶活性特征表明其对Cd毒性有一定的缓解作用。

Characteristics and Cd fractions of rhizospheric soil of Amaranthus hybridus L. under different cadmium concentrations

Amaranthus hybridus L. is Cd-tolerant plant. Here a pot experiment was carried out to investigate the effects of cadmium(Cd)stresses on the characteristics and Cd fractions of A. hybridus rhizospheric soil. Results showed that pH in the rhizospheric soil was lower than that in non-rhizospheric soil, while dissolved organic carbon(DOC) concentrations and catalase, urease and phosphatase activities were just opposite. Increasing Cd concentrations reduced pH and catalase activity, but increased DOC concentrations. With Cd concentrations increasing, exchangeable Cd fraction was increased, while iron and manganese oxides bound Cd fraction was decreased initially but increased later. Carbonates bound, organic matter bound and residual Cd fractions were all decreased. These results suggest that pH and DOC in rhizospheric soil of A. hybridus could be an important factor influencing the distribution of Cd fractions, and enzymatic activities in the rhizospheric soil could play a role in mitigating Cd toxicity.