镉在3种乔木中的积累及其亚细胞分布和化学形态研究

研究不同镉（Cd）浓度（0、25、50、100、200 mg·kg^-1）处理下，栾树（Koelreuteria paniculata）、臭椿（Ailanthus altissima）、银杏（Ginkgo biloba）3种乔木叶、枝、根中Cd的含量与积累特征，并分析Cd对其叶片超微结构的影响，探讨Cd在3种乔木叶片与根系中的亚细胞分布和化学形态特征.结果表明，3种乔木体内的Cd含量随着土壤Cd处理浓度的增加而增加，且主要积累在根部.栾树和臭椿各器官中的Cd含量显著高于银杏，表明栾树和臭椿对Cd的积累能力强于银杏.高浓度Cd处理下，栾树和臭椿叶片细胞结构损伤明显，细胞内出现大量黑色絮状物，且附着在细胞壁及细胞器的表面.而银杏叶片细胞无明显损伤特征，说明银杏对Cd的耐受性强于栾树和臭椿.3种乔木叶片中的Cd多存在于细胞壁或可溶性组分中，根系中的Cd多存在于细胞壁中，Cd在各组织的叶绿体、线粒体和细胞核等细胞器中分布较少.3种乔木叶片和根系中分别以移动性和毒性相对较低的HAc、NaCl提取态Cd分配比例最大.3种乔木各器官对Cd的积累能力与其叶片细胞中叶绿体与线粒体组分Cd占比有显著负相关关系，与叶片中HAc提取态Cd分配比例呈显著正相关性.

Accumulation, subcellular distribution and chemical forms of cadmium in three tree species

The concentration and accumulation of Cd in leaves, stems, and roots of Koelreuteria paniculata, Ailanthus altissima, and Ginkgo biloba were studied under different treatment levels of Cadmium(Cd) concentrations(0,25,50,100,200 mg·kg^-1). The influence of Cd on the ultrastructure in leaves was further analyzed. The subcellular distribution and chemical forms of Cd in leaves and roots of the three tree species were discussed. The results showed that Cd concentration in these three species of trees increased with the increase of Cd concentration in the soil, and the accumulation was mainly in the roots. The Cd concentration in the organs of Koelreuteria paniculata and Ailanthus altissima were significantly higher than that of Ginkgo biloba,indicating that the Cd accumulation ability of Koelreuteria paniculata and Ailanthus altissima were stronger than that of Ginkgo biloba. Under the treatment of high Cd concentration, the cell structure of leaves in Koelreuteria paniculata and Ailanthus altissima was obviously damaged, with large amount of black flocs appeared in the cells and attached to cell walls and the surface of organelles. However, there was no obvious damage in the cells of leaves in Ginkgo biloba, indicating that the tolerance of Ginkgo biloba to Cd was stronger than that of Koelreuteria paniculata and Ailanthus altissima. It was also found that Cd mostly existed in the cell wall or soluble components in the leaves of the three species of trees, and Cd mostly existed in the cell wall in the root systems. Cd was less distributed in organelles such as chloroplasts, mitochondria and nucleus. HAc- and NaCl- extracted Cd had the highest distribution ratio in leaves and roots of these trees respectively, with relatively low mobility and toxicity. The accumulation ability of Cd in each organ of the trees had a significant negative correlation with the proportion of Cd in chloroplast and mitochondria components in leaf cells,and a significant positive correlation with the proportion of Cd in HAc- extracted state in leaves.