镉(Cd)污染土壤的植物提取存在Cd有效性差及地上部积累量低等技术瓶颈，接种内生真菌是强化植物提取的重要手段。内生真菌印度梨形孢已被证明能够增强超富集植物东南景天对Cd的积累，提高Cd的植物提取效率。然而其强化机理目前尚不清楚。本项目以东南景天根系分泌物为切入点，采用离子色谱等技术研究接种印度梨形孢对东南景天根系分泌物产生量及组成的影响，通过梯度薄膜扩散技术分析接种菌株对根系分泌物Cd活化能力的影响，明确接种菌株提高土壤Cd有效性的机理。结合X射线吸收光谱、传统植物生理学方法研究接种印度梨形孢对东南景天根部Cd结合形态和根系非蛋白巯基肽的影响，探明接种菌株增强Cd向植物地上部转运的机制。从根系分泌物影响和根部Cd结合形态角度揭示内生真菌印度梨形孢强化东南景天积累Cd的机理，为理解内生真菌在植物提取中的作用提供新认识，为开展Cd污染土壤的微生物强化修复提供理论基础。

There are some critical problems in phytoextraction of cadmium (Cd) contaminated soil, such as low availability and limited contaminant uptake. Inoculation of endophytic fungi is an effective method for the enhancement of phytoextraction process. The Cd-phytoextraction efficiency of Sedum alfredii Hance has been reported to be enhanced by inoculating plants with Piriformospora indica but the mechanisms behind this process remain unclear. Thus, the overall objective of this project is to explore the mechanisms behind Piriformospora indica induced Sedum alfredii Cd accumulation. The effects of Piriformospora indica inoculation on the contents and components of root exudates will be determined by ion chromatography. Meanwhile, the effects of Piriformospora indica inoculation on the Cd mobilization ability of the root exudates will be evaluated by diffusive gradient in thin films technique. Then the mechanism of Cd mobilization in the rhizosphere induced by Piriformospora indica inoculation will be demonstrated. X-ray absorption spectroscopy will be performed to probe the effects of Piriformospora indica inoculation on the speciation of Cd in the roots of Sedum alfredii. Concentrations of non-protein thiols in the roots will be determined by traditional plant physiology methods. Then the mechanisms of the enhancement of transportation of Cd to the aerial part will be cleared. The mechanisms of Piriformospora indica inoculation enhances the accumulation of Cd by Sedum alfredii will be revealed by the changes of root exudates and Cd speciation in the roots. The results of this project are expected to provide new knowledge on the role of endophytic fungi in phytoextraction and to provide theoretical support for the microbe-assisted phytoextraction.