不同施肥模式下磷和AMF联合作用对农田Cd污染的原位固定修复及机理

In China, the serious heavy-metal contaminated lands are still intensely farmed for crop production due to the inconsistency between the increasing population and the decreasing land. Considering that even contaminated soils are a potential resource for agricultural production, it is of significance to develop a set of cropping systems to allow a safe and sustainable agriculture on contaminated farmlands while avoiding any transfer of toxic trace elements to the food chain. In the current protocols, mechanism and in situ stabilization of Cd-contaminated arable soils by AMF and the combined use of inorganic phosphate fertilizers and organic amendments are to be assessed. In greenhouse experiments, the dominant AMF Glomus mosseae in the local arable soil is to inoculate the maize under Cd stress and the Cd accumulation in the different tissues and organs of maize (Zea mays L.) is to subject to screen the AMF-maize association with low Cd accumulation under different fertilizer application style, in which the different amounts of phosphate supplements by the inorganic phosphate fertilizers and organic amendments is combined. The optimal AMF-maize association with lowest Cd accumulation will be targeted to assess the difference of the morphological characteristics, Cd accumulation behavior compared with the controls by transmission electron microscopy, synchrotron radiation X-ray fluorescence spectroscopy and X-ray absorption spectroscopy. Additionally, molecular mechanisms of Cd repartitioning in mycorrhizal plants are to be comparatively investigated by microarray and real-time PCR. The implementation of this project is to contribute to our knowledge and enrich the information on the management of rhizosphere microbiota to enhance the remediation of Cd-contaminated arable soil combined by mycoremediation and soil amendments, which is to provide important information on constructing a suitable model for the combined use of AMF-plant-fertilizer (soil amendments) to clean up heavy metal polluted arable soils.

针对我国地少人多、污染农田不能休耕的实际，采用农艺措施阻控重金属沿食物链传递对提高我国农产品质量安全具重要意义。基于此，本项目拟采用Tessier连续提取法和生物活性评价法对比研究不同施肥模式下磷和丛枝菌根真菌（AMF）联合作用对农田Cd污染原位固定修复效应，并从中筛选出玉米Cd低积累的"施磷-AMF"联合修复体系，探明施磷-AMF共同作用对农田土壤Cd离子钝化过程的化学形态变化特征，揭示减少植物根系Cd吸收的生理生态学基础；应用电镜、X-射线能谱等技术对比研究二者联合作用对改变宿主植物细胞、亚细胞Cd分布及分子形态变化，阐明提高宿主Cd抗性的细胞学基础；同时，利用基因芯片等方法研究施磷和AMF共同调控宿主Cd吸收、迁移、积累再分配分子机制。本项目实施将有助于丰富和拓展重金属污染农田土壤化学固定修复和微生物联合修复理论体系，为利用施肥-AMF-农作物联合修复Cd污染提供理论依据和技术支撑。

有机-无机肥配施是我国传统施肥制度的一大特色，对于重金属污染的农田土壤而言，在对农作物进行施肥的同时，其本身还可作为农田重金属污染土壤的化学修复剂（Soil amendments），可以有效改变农作物对重金属的吸收、迁移和积累。更为重要的是，有机-无机肥的合理配施在极大地改良土壤性能同时，还能激活农作物根际微生物活性，实现施肥、土壤污染物的化学修复和微生物修复三位一体的功能。基于此，在温室条件下，本研究以云南高原山区玉米主栽品种“会单四号”为实验栽培植物，模拟农田土壤重金属镉污染，研究接种AMF摩西管柄囊霉（Funneliformis mosseae）和配施有机-无机磷肥的共同作用对玉米Cd吸收积累的影响及机制。结果表明，施肥和AMF是影响玉米Cd的吸收、迁移积累的重要因子，但二者的趋势不同，发现与各自的对照组相比，单一施肥处理均显著增加玉米地上部分Cd的积累，而单一接种AMF处理减少了玉米植株地下部分的Cd浓度；在1倍施肥条件下，二者的联合作用最为显著，而过量施肥（5倍施肥量）AMF效应则受到抑制；进一步研究表明除了改善植物磷营养外，促进植物蛋白、果胶等NaCl提取态Cd的螯合转化、强化细胞壁的区室化作用是实现上述调控作用的生理生态基础；RNA-seq和生理酶学等相关数据表明，接种真菌通过调控宿主植物根际螯合、胞内区室化以及激活抗氧化系统活性等作用从而提高宿主重金属抗性。