| Among the group of the known metal-hyperaccumulators, Cd-hyperaccumulators are relatively a rare phenomenon in the plant kingdom, and hyperaccumulators are often described as low biomass, slow growth and could not accumulate multi-metals. However, weed plants display their characteristic of strong endurance to adverse environmental conditions, and high capacity to absorb water and fertilizes. In this sense, weed is an important type of ideal natural resources for the remediation of contaminated soils. The main aims of this study were to examine the growth responses of three Cd-hyperaccumulators Rorippa globosa, Solarium nigrum and Bidens pilosa and its accumulation characteristic of Cd and As under the condition of Cd-As combined pollution. To discuss the mechanisms of the interaction between Cd and As, so as to provide science foundation for remediation and treatment of Cd-As combined pollution.(1) In the present study, growth responses of Rorippa globosa and its accumulation characteristic of Cd and As were examined under the condition of Cd-As combined pollution. The results showed that Cd and As had an antagonistic effects on enhancing the growth of the plant and Cd uptake and accumulation under the low concentration of Cd and As treatments. However, there were synergic adverse effects on the plant growth and Cd uptake under the high concentration Cd-As combined pollution. Meanwhile, the accumulation of As in the roots were highter than that in the shoots, the translocation factor <0.3 and the bioaccumulation factor≤0.6.( 2 ) Solanm nigrum showed high tolerance to Cd under single treatments of Cd≤25 mg·kg-1, the height and shoot dry biomass of plants did not reduced significantly (p<0.05 ), and under low treatments of Cd-As combined pollution it could enhance plant growth. And the same time, it had the basic characteristics of Cd-hyperaccumulator. Growing in the presence of 10 mg·kg-1 Cd and 50 mg·kg-1 As, the plant height and shoot dry matter yields did not markedly decrease (p<0.05) compared to that at 10 mg·kg-1 Cd, however the stem Cd content increased by 28%. It also observed that S.nigrum used exclusion strategy to reduce As uptake in the root and restricted translocation into the shoots, resulting in As contents in the plant being root > leaf > stem > seed.(3) At all treatments of Cd-As combined pollution the growth of Bidens pilosa did not adverse effect significantly, and the dry aboveground biomass of plants showed a little increase at low concentrations of Cd-As combined pollution. Under a certain concentrations of treatments the contents of Cd in stems were more than 100 mg·kg-1, and the bioaccumulation factor and translocation factor were higher than 1.0, so the plant can be classified as a Cd hyperaccumulator, and also the plant had some characteristics of As excluder.
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