Cd、Zn交互作用对三七景天根系形态和重金属吸收积累的影响

Interaction of Cd and Zn Affecting the Root Morphology and Accumulation of Heavy Metals in Sedum aizoon

采取水培试验,研究了不同Cd、Zn浓度单一胁迫及其交互作用对三七景天生长、根系形态及Cd、Zn吸收和积累的影响.结果表明,三七景天对Cd、Zn单一胁迫均有较强的耐受性,其根、茎、叶各组织中Cd、Zn含量均随胁迫的增加而增加,且对Cd有较强的富集能力,地上部Cd含量可达133.0 mg·kg^(-1).Cd、Zn共同胁迫对三七景天生长的影响大于单一胁迫,而根系对其胁迫更为敏感,在Cd、Zn共同胁迫下其根系长度、表面积、体积和根尖数均显著降低,且对其根尖数的影响最为显著.Zn对三七景天地上部Cd吸收具有"低促高抑"效应,低浓度Zn(10 mg·L^(-1))对三七景天地上部Cd吸收有协同作用,促进Cd由根部向地上部转运.而添加Cd则对三七景天Zn吸收具有拮抗作用.Zn/Cd浓度比值对三七景天Cd吸收有显著影响,Zn/Cd比值较低时促进三七景天地上部Cd的积累,而高Zn/Cd比则抑制其Cd的积累.因此,三七景天具有较强的Cd富集能力,可应用于修复Cd污染土壤,而调节生长介质中Cd、Zn比例可促进三七景天对Cd的吸收效率.

A hydroponic experiment was conducted to study the interaction of Cd and Zn affecting the root morphology and accumulation of Cd and Zn in Sedum aizoon. The results show that S. aizoon exhibits a high tolerance to single stress of Cd and Zn and the concentrations of Cd and Zn in the leaf, stem, and root of S. aizoon increase as the stress levels increase. A strong phytoextraction capacity in S. aizoon was also observed for the Cd concentration in the aboveground part reaching 133.0 mg·kg^-1. The combined stress of Cd and Zn has a greater effect on the growth of S. aizoon than single stress to which the root is more sensitive. The root length, surface area, root volume, and tips significantly decrease under combined stress of Cd and Zn;the effect on the tips is most significant. The low-level Zn application (10 mg·L^-1) has a synergistic effect on the Cd accumulation in the shoot of S. aizoon because of the promotion of Cd translocation from root to shoot. However, the addition of Cd leads to a notable antagonism of the Zn absorption of S. aizoon. The concentration ratio of Zn and Cd also has a significant effect on the Cd uptake of S. aizoon. A high ratio promotes the Cd accumulation in the shoot, while the latter is inhibited by a low Zn/Cd ratio. Therefore, S. aizoon possesses a strong potential of Cd phytoextraction and can be applied for phytoremediation of Cd-contaminated soil, while the adjustment of the ratio of Cd and Zn in the growth medium will help to enhance the phytoremediation efficiency of S. aizoon.