2个镉耐性差异箭舌豌豆品种中镉的化学形态及亚细胞分布

通过溶液培养实验,研究了镉胁迫下2个箭舌豌豆(Vicia sativa)品种(镉耐性品种L3,镉敏感品种ZM)中镉的积累、镉的亚细胞分布和化学形态以及非蛋白巯基化合物(NPTs)的响应。结果表明2个箭舌豌豆品种根较地上部积累更多的镉。镉在箭舌豌豆根、茎和叶中主要分布于可溶性组分,敏感品种ZM根中可溶性组分的镉含量和占总镉的比例显著高于耐性品种L3。细胞壁结合镉占总镉的比例在2个品种中均为叶>茎>根。镉在箭舌豌豆根和茎内主要以去离子水(d-H2O)提取态和1 mol·L-1氯化钠(Na Cl)提取态存在,ZM根中d-H2O提取态镉的含量和比例显著大于L3。箭舌豌豆叶中镉主要以2%醋酸(HAc)提取态存在。ZM叶中80%乙醇提取态镉的比例大于L3,0.6 mol·L-1盐酸(HCl)提取态镉和残渣态镉的比例小于L3。2个品种根和茎中NPTs的含量在镉胁迫下显著升高,ZM根中NPTs的含量显著大于L3。研究结果表明,箭舌豌豆镉解毒的主要机制包括限制镉由根部向地上部转运和液泡隔离。此外,根和茎中镉与有机酸结合和NPTs螯合,叶中镉以移动性低、毒性低的形态存在也是箭舌豌豆镉解毒的重要机制。ZM较L3根中更多镉以移动性高的形态存在,L3较ZM叶中更多镉以难移动的形态存在,是L3较ZM具有更高镉耐性的重要原因。

Subcellular Distribution and Chemical Forms of Cadmium in Two Vicia sativa Varieties with Different Cadmium Tolerances

A hydroponics culture was conducted to investigate differences in cadmium (Cd) accumulation, subcellular distribution and chemical forms of cadmium, in addition to the changes of non-protein thiols (NPTs) in two Vicia sativa varieties (Cd-sensitive variety ZM, Cd-tolerant variety L3). Results showed that the shoot accumulated higher amount of Cd than the root in both varieties. Subcellular fractionation of Cd-containing tissues indicated that most of Cd was located in soluble fraction of roots, stems and leaves. Compared to L3, ZM contained higher amount and proportion of Cd in the soluble fraction of roots. Meanwhile, the proportion of Cd binding to the cell wall in leaves was higher than in stems and roots in both varieties. Results from sequential solvent extraction procedures showed that the most amount and proportion of Cd in roots and stems were present in the extraction of d-H₂O, followed by 1 mol L^-1 sodium chloride (NaCl). ZM had significantly higher amount and proportion of Cd than L3 in the d-H₂O extraction of roots. For the two varieties, most of the Cd was present in 2% acetic acid (HAc) extraction of leaves. Compared to L3, the proportion of Cd in the leaves of ZM was higher in the 80% ethanol extraction but lower in the 0.6 mol L^-1 hydrochloric acid (HCl) extraction and residues. The concentration of NPTs in roots and stems of both varieties was enhanced after being treated with Cd, especially for ZM. Therefore, the restriction of Cd translocation from the roots to the shoots and Cd compartmentation in vacuole might be responsible for the tolerance of Vicia sativa to Cd stress. The integration with organic acid and chelation with NPTs in roots and stems, and the formation of low mobility and low toxicity complexes in the leaves might also contribute to the Cd detoxification of Vicia sativa. The higher Cd tolerance of L3 than ZM might be associated with the higher proportion of low-mobility Cd in leaves (L3 vs ZM) and high-mobility Cd in roots (ZM vs L3).