Cadmium (Cd) and zinc (Zn) coexist in the environment but interact differently in plants. Cosmos bipinnatus has been potentially considered as a Cd-accumulator. Thus, this study investigated the detoxification mechanism in C. bipinnatus seedlings under Cd, Zn and Cd + Zn stresses. In the present study, the presence of Zn inhibited Cd uptake and translocation, whereas Cd merely hindered Zn uptake. The concentration of Cd in soluble fraction significantly decreased and Cd was bounded to the cell wall in root under Cd + Zn stress. Meanwhile, Zn and Cd mutually decreased their concentrations in the ethanol extractable form (FE) and water extractable form (FW) in roots and shoots. Furthermore, Cd + Zn stress enhanced the activities of superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.6) compared to Cd stress alone. These results suggested that Zn effectively decreased Cd uptake and translocation, changed their subcellular distributions, regulated their chemical forms composition and increased antioxidative enzyme activities, thereby enhancing the tolerance to Cd in C. bipinnatus. This study physiologically revealed the interactive effect of Cd and Zn on the detoxification mechanism of Cd in C. bipinnatus and provided new information on phytoremediation of the heavy metal contaminated soils.

中文翻译：

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在镉/锌复合胁迫下，锌的存在降低了大波斯菊幼苗中镉的吸收和转运。

镉（Cd）和锌（Zn）在环境中共存，但在植物中的相互作用不同。Cosmos bipinnatus已被潜在地视为Cd蓄积体。因此，本研究探讨了Cd，Zn和Cd + Zn胁迫下美加梭梭幼苗的解毒机理。在本研究中，锌的存在抑制了镉的吸收和转运，而镉仅阻碍了锌的吸收。Cd + Zn胁迫下，可溶性部分中的Cd浓度显着降低，Cd与根的细胞壁结合。同时，锌和镉在根部和枝条中的乙醇可萃取形式（FE）和水可萃取形式（FW）相互降低浓度。此外，Cd + Zn胁迫增强了超氧化物歧化酶（SOD，EC 1.15.1.1），过氧化物酶（POD，EC 1.11.1.7）和过氧化氢酶（CAT，EC 1.11.1）的活性。6）相比于单独的镉胁迫。这些结果表明，锌有效地降低了Cd的吸收和转运，改变了其亚细胞分布，调节了其化学形式的组成并增加了抗氧化酶的活性，从而增强了C. bipinnatus对Cd的耐受性。这项研究从生理学角度揭示了镉和锌的相互作用对双峰C中Cd的解毒机理，并为重金属污染土壤的植物修复提供了新的信息。