丛枝菌根真菌在稀土-重金属复合污染土壤植物修复中的作用机理研究

At present, rare earth resources development has caused serious ecological destruction and environmental pollution of mining areas in China. Remediation of soil co-contaminated with rare earth elements and heavy metals is a key problem. Arbuscular mycorrhizal fungi (AMF) have the potential to facilitate the process of phytoremediation of soil co-contaminated with rare earth elements and heavy metals. However, there are few studies focusing on the mechanisms and effects of arbuscular mycorrhizal fungi on the phytoremediation of soil co-contaminated with rare earth elements and heavy metals until now. Many new theories are urgent to be solved. In the present research, La, Pb and Calamagrostis pseudopbragmites, which are the dominant pollutants of soils and the dominant plant species from rare earth tailings area of Baotou, are selected as typical rare earth element, heavy metal and the tested plant. Firstly, the research is conducted to investigate the interactive effects of rare earth elements and heavy metals in soil-plant system. Then, pot experiments are conducted to screen effective AMF species applied to remediation of soil co-contaminated with rare earth elements and heavy metals. On the basis of these research results, further research is conducted to investigate the physical defense mechanism, the physiologycal and biochemical mechanism and the molecular-level mechanism of arbuscular mycorrhizal fungi on the phytoremediation of soil co-contaminated with rare earth elements and heavy metals using modern technique of environmental analysis and modern molecular biotechnology. The research of physical defense mechanism includes the effects of the intra and extra-radical mycelium of arbuscular mycorrhizal fungi on retention and filtration of rare earth elements and heavy metals. The research of physiologycal and biochemical mechanism includes the effects of arbuscular mycorrhizal fungi on the nutrition uptake by plant, photosynthesis, root morphology of plant, physical and chemical properties of rhizosphere, the chelation of glomalin, the activities of defense enzymes systems and PCs synthesis. The research of molecular-level mechanism includes the effects of arbuscular mycorrhizal fungi on the regulation of CpPCS1 gene expression. The research will explore the possibility of using of the technique of AMF-assisted phytoremediation in ecological restoration and environmental pollution control of rare earth mining areas. Moreover, the research will also provide theoretical basis and technical support to resolve the problems of ecological destruction and environmental pollution induced by rare earth mining of China.

我国稀土资源开发已导致矿区生态环境的严重破坏与污染，稀土重金属复合污染土壤的治理是关键。丛枝菌根真菌（AMF）具有促进稀土重金属复合污染土壤植物修复的潜力，但其作用机理研究尚属空白。本项目以包头稀土尾矿区主要污染元素镧、铅和优势植物假苇拂子茅为供试材料，模拟不同程度的稀土重金属复合污染胁迫，通过生物学盆栽试验研究土壤-植物系统中稀土重金属复合污染的交互作用，筛选适宜的AMF菌种；利用现代环境分析技术和现代分子生物学技术，分别从物理性防御机制（菌丝体的过滤固持作用）、生理生化机制（营养状况/光合作用/根系形态和根际环境/球囊霉素/防御酶活性/调节植物螯合肽的合成）、分子水平机制（调控相关基因的表达）等方面系统研究接种AMF在稀土重金属复合污染土壤植物修复中的作用机理。探索利用菌根技术进行稀土矿区生态恢复和环境污染控制的可行性，为解决我国稀土矿藏开采所带来的生态环境问题提供科学依据和技术支持。

我国稀土资源开发已导致矿区生态环境的严重破坏与污染，稀土重金属复合污染土壤的治理是关键。丛枝菌根真菌（AMF）具有促进稀土重金属复合污染土壤植物修复的潜力，但其作用机理研究尚属空白。本项目模拟不同程度的稀土重金属复合污染胁迫，通过生物学盆栽试验研究土壤-植物系统中稀土重金属复合污染的交互作用，筛选适宜的AMF菌种，分别从物理性防御机制、生理生化机制、分子水平机制等方面系统研究接种AMF在稀土重金属复合污染土壤植物修复中的作用机理。研究结果表明，La可显著降低土壤中EDTA提取态Pb浓度，增加植株中Pb浓度；Ce可显著增加土壤中EDTA提取态和植株中Pb浓度；Pb可显著降低土壤中EDTA提取态和植株地上部La和Ce浓度。综合分析5种AMF对根系侵染率、生长、矿质营养、稀土和重金属吸收等方面的影响，筛选出C. etunicatum作为进一步研究的适宜菌种。研究结果显示，接种AMF显著地减轻了稀土重金属复合胁迫对植物的毒害作用，显著提高了植株生物量和P含量，显著降低了植株C:P和N:P，显著提高了植株叶片SOD、CAT、POD等抗氧化酶活性，显著增加了MDA含量和渗透调节物质PRO、可溶性蛋白含量，提高了根际土壤pH值和易提取球囊霉素、总球囊霉素蛋白含量，没有显著影响叶片GSH和叶绿素含量，显著改变了植物根际土壤细菌和真菌的丰富度和多样性，从而影响了根际土壤菌群结构，显著上调了植物体内螯合蛋白合成酶基因PCS的相对表达量。研究结果表明，接种AMF可显著影响复合污染胁迫下稀土重金属在土壤-植物系统中交互作用的类型、程度及对稀土或重金属的吸收和转运，与稀土、重金属元素种类和土壤中浓度有关。结果表明，AMF和植物根系共生可以显著影响共存金属元素的生物可利用性、植物毒性及生态风险，对于更好的理解AMF在稀土重金属复合污染土壤植物修复中所发挥的作用具有十分重要的意义；为探索利用菌根技术进行稀土矿区生态恢复和环境污染控制的可行性，为解决我国稀土矿藏开采所带来的生态环境问题提供了科学依据和技术支持。