巯基化合物在万寿菊镉解毒中的作用

采用水培实验方法研究了万寿菊体内镉积累和解毒与巯基化合物含量的关系。万寿菊植株分别在镉浓度为0、0.1、0.5、2和8 mg/L的营养液中暴露7 d,测定了根、茎、叶中镉、非蛋白巯基(NPT)、半胱氨酸(Cys)、γ-谷氨酰半胱氨酸(γ-EC)、谷胱甘肽(GSH)和植物络合素(PCs)的含量。植物根、茎、叶中镉含量都随着镉暴露浓度的增加而增加。当溶液中镉浓度较低(0.1～2 mg/L)时,茎叶中NPT、PCs、Cys和γ-EC含量随着镉浓度增加而增大;当镉浓度较高(8 mg/L)时,茎叶中PCs含量迅速降低,GSH含量大幅度增高。在根部,这些巯基化合物的含量几乎不受镉处理影响,且含量较低。以上研究结果表明:PCs在万寿菊镉的解毒机制中发挥一定的作用,暴露于高浓度的镉,GSH比PCs起着更为重要的解毒作用。

The role of thiol pool in cadmium detoxification in marigold plants

The relationship between thiol-containing compounds accumulation and cadmium (Cd) detoxification was studied. Studies were carried out with marigold ( Tagetes erecta L. ) plants grown in the presence of 0.1,0.5, 2, 8 mg/L Cd for 7 days. Contents of cysteine (Cys), γ-glutamyl-cysteine (γ-EC ) , glutathione (GSH) , phytochelatins (PCs) and non-protein thiols ( NPT) , and Cd accumulation in the root, stem and leaf were determined. Cd contents increased in the plant with the increase of Cd exposure concentration. From 0.1 to 2 mg/L Cd, contents of NPT, PCs, Cys and γ-EC in stems and leaves significantly increased with increasing Cd doses. However, at the dose of 8 mg/L, the synthesis of PCs in the stem and leaf decreased drastically, and the GSH pool increased significantly. In the root, contents of these thiol-containing compounds were lower and less affected by Cd treatments. These results indicate that PCs play some roles in Cd detoxification, but PCs-mediated chelation are not the most effective strategy to cope with an exposure to toxic levels of this metal.