八宝景天镉富集的生态分异及环境调控机制

Hylotelephium spectabile, a promising Cd accumulator with wide range of ecological adaptation, has the potential in phytoremediation of Cd-contaminated soil in north and south China. However, our previous studies showed that the Cd accumulation capacity of H. spectabile among different ecotypes is quite different. Moreover, different external environmental factors between different climatic regions in north and south also show different influence on Cd phytoextraction of H. spectabile. Therefore, in order to improve the application potential of H. spetcabile for phytoremediation of Cd-contaminated soil, this project aims to clarify the transport characters in different ecotypes of H. spectabile under the control of environmental factors. The ion chromatography will be performed to probe the contents and components of root exudates between different ecotypes of H. spectabile under different light, temperature and soil moisture conditions. Meanwhile, the regulation mechanism of environmental factors on Cd transport in root and xylem will be determined by X-ray absorption near edge structure. The results may help to improve the Cd accumulation efficiency of H. spectabile via modifying the environmental factors and has important theoretical and practical value for H. spectabile application in phytoremediation of mild and moderate Cd-contaminated soil in China.

镉富集植物八宝景天生态幅度广，具有修复我国南北方Cd污染土壤的应用潜力。前期研究发现不同生态型八宝景天Cd富集能力差异较大，且在南北方不同气候环境下对Cd积累有不同的响应特征。鉴于此种情况，本项目以提升八宝景天Cd富集效率为目标，明确环境因素调控下，Cd在不同生态型八宝景天中的迁移特征。因此，本研究以Cd富集型和非富集型八宝景天为研究对象，通过模拟光照、温度、水分等环境因素，分析八宝景天对光合、蒸腾等生理特征的响应机制，采用离子色谱等技术分析八宝景天根系分泌特征及其对根系Cd吸收的影响，通过同步辐射等技术研究Cd在八宝景天根部和木质部微观运输机制。研究结果将有助于通过调控环境因素提高八宝景天Cd修复效率，对八宝景天修复我国中低度Cd污染农田具有重要的理论及应用价值。

本研究以不同Cd富集能力的八宝景天生态型为研究对象，结合室内和田间试验，揭示不同生态型八宝景天Cd吸收转运的内在机理和光照、土壤水分、养分、盐分等关键环境因素对其Cd富集过程的调控机制。结论如下：（1）在北方典型Cd污染土壤上研究环境因素调控下，HB1和LN两种八宝景天生态型生长和Cd吸收的响应，结果表明，LN生态型在各生育期和环境调控下其叶片蒸腾速率均保持较高水平且较HB1显著高17.3%~444.5%，使其Cd富集量较HB1高59.6%。此外，LN生态型对氮素供应的光合速率响应较HB1更积极，进一步放大了其生长和Cd富集的优势。适度干旱可刺激LN生态型根系生长，使其具有更强的应对水分胁迫的能力，而光照处理主要调控Cd在八宝景天体内各组分的迁移和分配。（2）选取六种不同Cd富集能力的八宝景天生态型，在北方典型Cd污染土壤上研究不同盐分胁迫下其生长和Cd富集特征，结果表明，LN生态型在高浓度盐分胁迫下（1%NaCl）仍未表现出明显的生长抑制，且地上部Cd含量较其他生态型显著提高24.8%～322.3%，在盐分胁迫下保持较高的光合、蒸腾速率和气孔导度可能是其较HB1具有更高Cd富集和耐盐分胁迫能力的重要作用机制。（3）对土壤理化性质和矿质元素对八宝景天根际特征和Cd富集的影响开展田间试验，结果表明，八宝景天Cd吸收主要受土壤有效态Cd、Zn含量调控，同时与其体内Mn、Zn、Cu的吸收存在协同效应，而与其Ca吸收则存在一定的竞争关系。（4）北方典型Cd污染土壤上，对养分（N、P、K）调控对八宝景天生长和Cd吸收开展田间验证试验，结果表明，土壤养分促进八宝景天Cd富集主要通过提高其生物量且主要受N水平调控。同时，K一定程度上可促进八宝景天Cd吸收，N和K对其Cd富集具有明显的交互作用，高量N配施适量P、K可使八宝景天Cd富集量提高1~2倍，是提高其Cd富集效率的最佳养分调控措施。.综上，LN生态型八宝景天在环境调控下光合特征响应较HB1更为积极，使其具有更强的Cd富集和耐环境胁迫的能力，可应用于生态幅度更广泛的Cd污染土壤修复。