不同生境下锌镉在伴矿景天不同叶龄叶中的富集与分布特征

田间试验、温室盆栽和生长室水培试验研究了Zn和Cd超富集植物伴矿景天不同叶龄叶片的Zn、Cd富集和分布特征。结果显示，田间条件下伴矿景天新叶中Cd浓度高于成熟叶、但新叶中Zn浓度低于成熟叶。温室盆栽试验发现，连续种植伴矿景天，第4季时低污染土壤（S1）上新叶中Zn浓度低于成熟叶，但高污染土壤（S4）上新叶中Zn浓度高于成熟叶；而到了第6季，S1、S4上新叶中Zn浓度均低于成熟叶，且在S1上两者达到显著水平；第4和第6季，伴矿景天新叶中Cd浓度始终高于成熟叶（除S1成熟叶中Cd浓度略高于新叶外）。水培试验结果发现，无论在高Zn（600 mmol/L）、高Cd（100 mmol/L），还是低Zn（10 mmol/L）、低Cd（1 mmol/L）处理，新叶中Zn、Cd浓度均高于成熟叶；而且随着处理时间的延长，新叶和成熟叶中Zn、Cd浓度均明显上升。水培条件下，新叶和成熟叶中Zn最高分别为43 107、33 774 mg/kg（以干重计）（600 mmol/L，处理56 天）；新叶和成熟叶中Cd的最高浓度分别为15 057、9 060 mg/kg（以干重计）（100 mmol/L Cd，处理56 天）。这些结果表明，Zn、Cd在伴矿景天新叶和成熟叶中富集和分布与其生长介质中Zn、Cd的浓度尤其是有效态浓度、处理时间及植物所处的生长阶段等有关，同时也表明Zn、Cd优先分布于新叶可能与伴矿景天超富集Zn、Cd的机制有关。

Characters of Zn and Cd accumulation and distribution in leaves of Sedum plumbizincicola at different ages

Field plot experiment, pot trial and hydroponics culture were conducted to study the accumulation and distribution characters of Zn and Cd in the leaves of Sedum plumbizincicola at different ages. The results showed that young leaves had higher Cd concentrations than mature one when grew at field plot, but the situation was opposite for Zn. Glass house pot experiment results showed that for fourth extraction season, Zn concentrations appeared to be higher in mature leaves than young ones when Sedum plumbizincicola grew at low Zn and Cd contaminations soil (S1), Zn concentrations in young leaves were higher than in mature one when plants grew at high Zn and Cd contamination soil (S4). For the sixth extraction season, Zn concentrations in mature leaves were significantly higher than in young ones at both S1 and S4. For both seasons, Cd concentrations in young leaves were significantly higher than in mature ones, except for the sixth extraction season of S1. Under hydroponics culture condition, Zn and Cd concentrations in young leaves were all higher than in mature ones. Cd and Zn concentrations in both mature and young leaves increased with incubation time, peaked at day 56 d, in mature and young leaves the highest concentrations of Zn were 43 107 and 33 774 mg/kg (DW) (600 mmol/L Zn) while and the highest concentrations of Cd were 15 057 and 9 060 mg/kg (DW), respectively. These results showed that accumu- lation and distribution characters of Zn and Cd in young and mature leaves were related to Zn or Cd concentrations in growth medium, especially to soil available Zn or Cd concentrations, treated time of heavy metals, plant growth stage. Sedum plumbizincicola has preferential allocation habit of Zn and Cd into shoots, especially into young leaves.