农田土壤硒铬互作的生物效应及其影响机制

Selenium (Se) is considered a beneficial element for plant, and several studies have demonstrated that the positive effects of Se become evident especially in plants subjected to internal and external oxidative stressors. Chromium (Cr) is a common heavy metal pollutants in the soil. In the previous studies, we found that supplementation of Se at trace concentration protected plant against relatively high Cr doses, and decreased the content of Cr in plant. Similar with other’s foundings, the accumulation of Se in plant is increased with the stress of Cr. We can come to complex interactions between Se and Cr from this result. However, the mechanism of the biological effects and its influence is not clear, with the interaction of Se and Cr in soil. In this study, base on the previous studies, the biological effect of Se and Cr interaction in representative farmland soil will be revealed. Moreover, XAFS, SEM-EDXA and μ-XRF techniques will be used to dertermine the distribution of Se and Cr in the inetrface between soil and root, and to determine the environmental chemical behavior such as molecular morphology, migration and transformation, adsorption and desorption. In addition, determine the root exudates of metabonomics to reveal the physicochemical regulation mechanism of biological effect with Se and Cr interaction in rhizosphere using GC-MS techniques; and determine the microbial community diversity to reveal the miceobial ecological mechanism using 16S rDNA、T-RFLP techniques. It will be important to promote the safe use of Se and provide a theoretical basis in the heavy metal polluted of farmland.

硒是植物生长的有益元素，已被证实可增强植物的抗逆能力。铬是土壤中常见的重金属污染物。本项目组前期研究发现：硒可有效缓解植物铬的毒害，并降低铬在植物体内的积累；与同类研究结果类似：铬胁迫促进了硒在植物体内的积累。该现象表明硒铬间存在复杂的交互作用，然而，土壤中硒与铬互作的生物效应及其影响机制尚不清楚。本项目拟在前期研究的基础上，结合硒与铬的土壤环境化学特征，研究典型农田土壤硒铬互作的生物学效应；并综合应用XAFS、SEM-EDXA、μ-XRF等技术探讨根土界面硒铬的微区分布、土壤铬的原位分子形态、迁移转化、吸附与解吸特征等环境化学行为，联合GC-MS技术分析根系分泌物的代谢组差异，揭示土壤硒铬互作生物效应的根际理化调控机制；应用16S rDNA、T-RFLP技术研究硒铬互作对土壤微生物群落多样性的影响，揭示硒铬互作生物效应的根际微生物生态机制。为推动硒在重金属污染农田的安全利用提供理论依据。

硒是植物生长的有益元素，已被证实可增强植物的抗逆能力。铬是土壤中常见的重金属污染物。本项目组前期研究发现：硒可有效缓解植物铬的毒害，并降低铬在植物体内的积累；铬胁迫促进了硒在植物体内的积累。土壤中硒与铬互作的生物效应及其影响机制尚不清楚。本项目系统研究了铬污染条件下外源硒对植物生长、光合特性、硒铬吸收与转运特征、根际土壤中铬的微区分布等的影响；深入分析了硒铬互作体系中元素有效态含量与土壤理化因子的关系；明确了硒铬互作条件下环境因子对土壤微生物群落的影响，并阐明了根际微生物对根系中硒、铬有效性的调控；硒铬互作下植物介导的土壤中的有机物的变化及其与硒铬有效性之间的因果关系；深入分析由硒铬交互引起的土壤理化性质变化与元素吸附解析特征之间的关系。. 研究结果表明：(1) 外源硒降低了铬对植物的光合功能，维持了植物的生长；在高浓度铬污染下，硒铬互作降低了土壤铬的生物有效性，进而减少了铬在植物体内的积累；(2) 铬污染造成植物有机酸分泌量增多，还原糖含量减少；硒单独作用下，增加了根际土壤纤维二塘的含量；铬污染条件下，硒增加了Cis-9,10-Epoxystearic acid和十六烷二酸的相对含量；根际过程显著影响植物生长与硒铬互作特征，硒未对土壤铬的分子形态产生显著影响；三价铬与硒在土壤中相互促进彼此在土壤中的吸附，六价铬则与硒都是以阴离子的形式存在于土壤中；(3) 根据16Sr RNA高通量测序结果，Se改变了高浓度Cr污染土壤中微生物群落的功能，进而影响其对Cr的转化能力及其在土壤中的有效性。硒处理下，微生物群落对三价Cr的还原能力增加，是土壤有效铬降低的原因；根际土壤环境因子共同调控土壤微生物群落结构，进而影响土壤硒铬的有效态含量。. 项目系统研究了土壤硒铬交互作用的生物学效应，深入解析了土壤中硒铬互作生物学效应的影响机制。为缓解作物铬毒害、降低农产品铬含量、提高硒含量，确保农产品安全优质生产和农田生态环境安全提供理论参考。