耐性植物根际微域西玛津脱毒过程及其生态化学耦合作用机制

In accordance with the realistic meaning for remediation the soil polluted by triazine herbicides, the deficiency in the research to phytoremediation and its rhizosphere coupling effect on triazine herbicides contaminated soil, and controling the environmental risk of triazine herbicides contaminated soil. Combining simazine as a representative in wide used triazine herbicides in China and the preliminary results that pennisetum has potential to rhizosphere remedy simazine contaminated soil found by our and other research group, simazine and pennisetum will be selected as contaminant and plant objects in the present project, respectively. In accordance with the primary research result in plant rhizosphere phytoremediation to organic chemicals polluted soil and the efftcts of root exudate on pyene degradation and its mechamism by our research group, a hydroponic experiment, a indoor simulating cultivating experiment, a multi-interlayer rhizobox experiment and a rhizosphere simulating experiment will be combined to apply in the present project, to deeply probe into the components and its content in special root exudate of pennisetum which are response to simazine stress, simazine distribution charactertics after uptaking by pennisetum, solubilization effect to of pennisetum and its reaction mechanism, degradation effect to simazine affected by enzyme in root exudate, spacial characteristics of simazine degradation and relevant soil microorganism ecological evolvement with the different millimeter distance from the pennisetum root surface, and effects of pennisetum root exudate on simazine degradation and relevant characteristics of soil microorganism ecological evolvement induced by pennisetum root exudate in the simazine contaminated soil. Therefore, it will reveal the interactive relationship among special root exudate of pennisetum, soil microorganism ecological evolvement and the ecological chemical behavior of simazine, clarify the rhizosphere coupling system play a key role in self-purification process of simazine contaminated soil and its eco-chemical mechanism, and clarify the extent of rhizosphere effect. At last, the results as above will improve the academic base and technical support in enriching and developing rhizoremediation technique to triazine herbicides and other organic compounds contaminated soil.

针对三嗪类除草剂污染土壤植物修复根际效应机制的研究不足，以及控制其污染土壤环境风险的现实意义，本项目以在我国广泛使用的三嗪类除草剂代表性化合物之一的西玛津和对其具有较强耐性和修复潜力的狼尾草为研究对象，综合采用水培、室内模拟培养、多隔层根箱培养和根际模拟试验等研究方法，深入探讨西玛津胁迫下狼尾草根系特异性分泌物组成和数量响应，特异性分泌物对西玛津的增溶作用和机制及分泌物中酶对西玛津降解的作用特征，狼尾草根际微界面土壤中西玛津的空间消减规律和相应的微生物学性状演替特征及狼尾草对西玛津的吸收分配特征，特异性根系分泌物对土壤中西玛津降解的影响及其诱导产生的微生物学性状演替特征等，揭示狼尾草特异性根系分泌物、根际微生物学性状演替及西玛津消减行为三者之间的相互关系，阐明狼尾草对西玛津胁迫的根际效应响应特征对西玛津消减的作用及其生态化学机制，为发展三嗪类除草剂污染土壤根际修复技术提供理论依据。

针对三嗪类除草剂污染土壤植物修复根际效应机制的研究不足，以及控制其污染土壤环境风险的现实意义，本项目以西玛津和对其具有较强耐性的狼尾草为研究对象，阐明狼尾草对西玛津胁迫的根际效应响应特征及其对西玛津脱毒消减的作用和根际效应的生态化学耦合作用机制。.研究发现：种植狼尾草可明显促进土壤中西玛津的降解，其机制主要是与植物的根际效应有关，与植物吸收积累无关。根际西玛津降解的整体趋势表现为：近根层>根生长层（根室）>远根层，其机制与土壤微生物随根际距离梯度的变化和微生物对根系分泌物剂量变化的响应高度一致。西玛津胁迫下，其根系分泌物组分含量发生特异性的变化，主要组分（低分子有机酸、总糖、氨基酸、酶）总体随西玛津胁迫浓度升高而显著上升，根系分泌物对西玛津具有明显的增溶作用，可抑制土壤对西玛津的吸附，增溶贡献主要来自狼尾草系分泌物中大分子组分（>8000Da）；西玛津在狼尾草的降解空间特征与根系分泌物剂量效应密切相关，狼尾草通过其根系分泌物调控土壤微生物群落、数量和活性来影响根际西玛津的降解，狼尾草根际西玛津的降解以细菌为主，狼尾草根系主要通过分泌物影响细菌群落的数量，进而影响着西玛津的降解变化特征。同时研究发现，一定根系分泌物浓度范围内,根系分泌物促进土壤革兰氏阴性细菌特有群体感应信号分子AHLs及革兰氏阴性和革兰氏阳性细菌共有群体感应信号分子AI-2活性，特别是调控土壤革兰氏阴性细菌的种群与数量及其参与土壤中西玛津的降解。种植狼尾草可显著增加根际土细菌群的功能多样性和群落结结构的多样性，特别具备较强西玛津降解能力的微生物，如显著提升Arthrobacter(节杆菌属)的丰度。综上可见，狼尾草根系分泌物对西玛津的增溶作用、根系分泌物对土土壤微生物群落、数量和活性的调控作用及其互动关系是狼尾草根际西玛津快速消减及其消减规律的核心生态化学耦合机制。上述研究结果为丰富和发展土壤西玛津污染的根际原位修复技术提供了坚实的理论依据。