Abstract:

Sedum alfredii Hance has been identified as a new Zn-hyperaccumulator native to China. In this study, responses and metal accumulation of S. alfredii were examined under Zn/Cd complex polluted conditions. The results showed that optimal growth of S. alfredii in terms of the maximum dry matter yield was observed at Zn/Cd complex level of 500/100 祄ol/L. Plant cadmium (Cd) or zinc (Zn) concentrations increased with increasing Cd or Zn supply. During the 20 d treatment, the highest Cd concentration in the leaves reached 12.1 g/kg at Zn /Cd level of 50/400 祄ol/L and that of Zn in the stems was 23.2 g/kg at Zn/Cd level of 1 000/50 祄ol/L. The distribution of Cd in different plant parts decreased in the order: leaf ＞ stem≥ root, whereas that of Zn was: stem ＞ leaf ≥ root. The accumulation of Cd and Zn in the shoots and roots of S. afredii increased with the increasing of Zn/Cd supply levels, peaked at Zn/Cd levels of 250/400 and 500/100 祄ol/L, respectively. The highest Cd and Zn uptake by the shoots was approximately 5 and 11 mg/plant, and was over 20 and 10 times higher than those in the roots, respectively. Zn supply at levels ≤ 500 祄ol/L increased plant Cd concentrations, whereas high Zn supply decreased root Cd but did not affect leaf Cd concentrations in S. alfredii. Low Cd supply increased Zn concentration in the leaves, but Cd supply higher than 50 祄ol/L considerably reduced root Zn concentrations, especially at low Zn level. These results indicate that S. alfredii can tolerate high Zn/Cd complex levels and has an extraordinary ability to hyperaccumulate not only Zn but also Cd. It could provide a new valuable plant material for understanding the mechanisms responsible for co-hyperaccumulation of Zn and Cd as well as for phytoremediation of the Cd/Zn complex polluted soils.

东南景天对锌、镉复合污染的反应及其对锌、镉的吸收和积累特性
叶海波  杨肖娥  何 冰  龙新宪  石伟勇
（1.浙江大学环境与资源学院, 杭州 310029；2.广西大学农学院, 南宁 530005）

摘要: 东南景天（Sedum alfredii Hance）已被鉴定为一种中国原生的新的锌超积累植物。 本文主要研究了锌(Zn)、镉(Cd)复合处理水平对东南景天的生长及其对锌、镉的吸收积累特性的影响。 结果表明，在Zn/Cd复合水平为500/100 μmol/L时，植物生长最佳。Zn/Cd在东南景天叶片、茎部和根系中含量随着Zn/Cd处理水平的提高而增高。在Zn/Cd 复合水平为50/400 μmol/L时茎叶中Cd含量达最高，其中叶片Cd含量达12.1 g/kg；在Zn/Cd 复合水平为1 000/50 μmol/L时茎叶中Zn含量达最高, 其中茎中Zn含量达 23.2 g/kg。 植株各部位Cd含量的分布为:叶片＞茎＞＞根系，而Zn在体内的分布为: 茎＞叶片＞＞根系。 Zn、Cd在地上部和根部的积累量也随着处理水平的提高而增加，分别在Zn/Cd复合水平为250/400和500/100 μmol/L下达高峰值。 东南景天地上部积累最高Zn和Cd的量分别达11和5 g/plant, 其比根系的积累量分别大10和25余倍。 Zn、Cd对东南景天的生长、吸收积累的相互作用依赖于Zn/Cd复合水平和植物部位。 在适宜Zn/Cd 处理水平范围内，Zn和Cd的吸收和积累具有相互促进作用。 高Zn或高Cd处理均抑制了植物对Zn和Cd的吸收和积累。 本研究结果表明，东南景天不仅具有忍耐高Zn/Cd复合污染，而且具有超量积累Zn和Cd的特异能力。 它为进一步研究植物Zn、Cd超积累的机理和Zn/Cd复合污染土壤的植物修复提供了一种新的材料。
关键词： 复合污染; 镉; 锌; 超积累; 东南景天

通讯作者。 E-mail: <xyang@zju.edu.cn>。