镉在草地早熟禾中的分布和化学形态研究

为探究草地早熟禾(Poa pratensis L.)对重金属镉(Cadmium, Cd)的分配和耐受机制，以草地早熟禾耐Cd品种‘午夜’(‘Midnight’,M)和Cd敏感品种‘橄榄球2号’(‘Rugby II’,R)为试验材料，在水培条件下施加600μmol·L^-1Cd胁迫，研究Cd在草地早熟禾中的组织分布、亚细胞分布及化学形态。结果表明，与R品种相比，Cd胁迫下M品种叶片失绿较少，生长抑制较小；表皮+叶肉、维管束及根表皮+皮层中的Cd含量显著低于R品种；另外，根系可溶部分Cd含量高于R品种。进一步分析发现，R品种含有更多毒性较高的无机态Cd及果胶和蛋白质结合态Cd,而M品种水溶性有机酸结合的Cd在根表皮+皮层、中柱等组织中含量较多，草酸盐结合的Cd在根系中柱含量显著高于R品种。因此，M品种通过减少Cd吸收、增加液泡区隔化、增加有机酸盐结合的Cd并降低Cd向地上的长距离运输来增强对Cd的抗性。

Study on Distribution and Chemical Forms of Cd in Poa pratensis

To investigate the Cd distribution and tolerance mechanisms in Kentucky bluegrass，the Cd-tolerant and Cd-sensitive cultivars named Midnight (M) and Rugby (R) were used as the experimental materials. The distribution and chemical forms of Cd in tissue and subcellular at a hydroponic culture condition were studied under 600 μmol·L^-1Cd stress. The results showed that M genotype had less leaf chlorosis and growth inhibition under Cd stress compared with R genotype. The Cd concentrations in epidermis + mesophyll,vascular bundle,and rhizodermis + cortex of M genotype were significantly lower than that of R genotype. In addition,the soluble Cd concentrations in roots of M genotype were higher than that of R genotype. The inorganic Cd,pectinate and protein bound Cd in R genotype were higher than those in M genotype,while the M genotype had higher concentration of water-soluble organic acid bound Cd in rhizodermis + cortex and stele,and oxalate-bound Cd in stele. Therefore,the M genotype increased Cd tolerance by decreasing the absorption of Cd,increasing the vacuolar compartmentation,organic acid bound Cd,and decreasing the long-distance translocation of Cd from roots to shoots.