菌根际微界面效应及其对宿主植物重金属转运过程的趋向调控机理

Based on the current situation that cadmium-contaminated soil becomes an especially severe environmental problem in our country while hyperaccumulators are hard to be applied in large region, a dominant plants in cadmium-contaminated sites, Phragmites australis (common reed) was chosen as host plants for arbuscular mycorrhizal fungi (AMF). AMF could effectively improve the heavy metal stress resistance capability and metal translocation efficency of their host plants, therefore the establishment of AMF-plant symbiotic system is necessary for the remediation of metal-contaminated environment. The present research focused on the symbiotic relationships between AMF and plants with different accumulation characteristics.The distribution pattern, chemical speciation and concentration variation of cadmium in the complicated system composed of substrate-AMF-plant were also quantitatively investigated. Moreover, the trend of cadmium translocation in plants with different accumulation characteristics were also revealed. In addtion, the AMF-induced improvements in plant rhizosphere conditions and regulations in rhizospheric microbial community structure, as well as their significant role during the immobilization, uptake extration and accumulation process of heavy metals were analyzed and explained deeply. Furthermore,the tendency regulation mechanisms of mycorrhizosphere micro-interfacial effects on the translocation pathway of heavy metal in the host plant were illustrated. The main conclusions of the present research will enrich the content of the ″translocation pathway choice hypothesis of heavy metal", conduce to the explorations of the artificial mycorrhiza-based biotechnologies and methods aimed at metal-contaminated environment remediation, and contribute to the development of the new theories and innovations which are appropriate to be extensive applicated in the bioremediation of cadmium-contaminated environment, finally, to enhance the governance capacity of heavy metal pollution in our country.

针对我国镉污染土壤面积广泛、原生植被退化严重而重金属修复效率低下的现状，利用丛枝菌根真菌（AMF）可有效提高宿主植物抗重金属胁迫能力、改变植物对金属元素转运效率的特性，构建AMF-植物共生体系联合修复重金属。重点研究AMF与不同富集特征植物的耦合关系，定量追踪镉在基质-AMF-植物这一复杂系统中的分布格局、赋存形态及其剂量变化，揭示不同富集特征植物对金属镉的运转规律，深度解析AMF对植物根际微环境的改造功能、对根际微生物群落结构的调控功能，及其在重金属固定、吸收、提取以及富集过程中发挥的重要作用，揭示AMF的微界面效应及其对宿主植物重金属转运过程的趋向调控机理，丰富“重金属转运路径选择假说”，探索基于菌根生物技术的人工强化重金属修复技术手段，创建一种适合大面积推广应用的镉污染生物修复新理论和新方法，提高我国重金属污染治理能力。

针对我国重金属污染异常严峻而治理能力普遍低下的现状，利用丛枝菌根真菌（AMF）可有效提高宿主植物抗重金属胁迫能力、改变植物重金属元素利用运移能力的特性，构建AMF-植物共生体系联合修复重金属。.结果表明，筛选到的广适性菌根真菌可与宿主植物-芦苇形成稳定共生关系，AMF的侵染可显著提高宿主植物种子萌发、生长发育和存活率，促进宿主植物的定植与生长，提高营养元素吸收与资源同化效率，并修饰根际微环境条件及微生物群落组成。.Cd胁迫条件下，AMF-芦苇共生体系的形成，可通过维持植物生长参数、提高净光合速率及最大净光合速率、降低蒸腾速率和部分气孔关闭等策略来缓解Cd对宿主植物的生理胁迫。同时，可通过减弱在芦苇根系和茎中Cd胁迫对Mn元素的影响，促进叶片P的吸收帮助宿主植物抵抗Cd胁迫。.宿主植物芦苇属于“权衡型植物”，在低/高Cd胁迫条件下，接种AMF会分别促进/抑制芦苇根系中对Cd的吸收。微区分析结果表明，接种AMF处理通过增加Cd沉积在细胞壁表面及（或）区隔在液泡中，降低了在细胞器中的Cd分布来缓解Cd对宿主植物细胞器造成的损伤。AMF接种处理显著提升了宿主植物体内各营养器官中的钝化态（难溶解态、草酸盐态和残渣态）Cd的浓度及比例。.生理机制分析结果表明，AMF会显著降低丙二醛（MDA）和脯氨酸（Pro）活性来缓解Cd胁迫对宿主植物细胞内的氧化应激。PCA分析发现AMF参与Cd改变自身抗氧化防御，Cd与巯基基团的结合干扰生理过程，及Cd占据必需元素转运通道或位点导致相关功能失效这3种途径来缓解Cd胁迫对宿主植物芦苇根系造成的植物毒性，提高宿主植物对Cd的耐受性。.总之，AMF-芦苇共生体系，不仅能够缓解Cd胁迫对芦苇生长发育的抑制，还能通过调节Cd的吸收与转运提高对Cd的耐性，为AMF-植物联合修复重金属污染提供了新的理论支持和实践指导思路，填补了传统植物修复技术在实际应用中的不足。