荒漠草原群落中不同生态位植物根系分泌物的根际效应及其有效组分的筛选

Root exudates are key factors that maintain the vitality of micro-ecosystem rhizosphere and constitute the different plant rhizosphere characteristics. This study intends to clear the rhizosphere effects of five species plants in Stipa desert grassland communities in different ecological niche, and screening their effective components. We will collect and extract plant root exudates by hydroponics and analyze their components and contents using gas chromatography-mass spectrometry. Under the premise of the five kinds of plant root exudates characteristics, we will use chemical reagents to simulate the component of root exudates, then the five kinds of plant root exudates and their chemical mimetic of component will be added to the soil taken from desert grassland, and cultured in the laboratory. Using high-throughput sequencing analyze genious the soil microbial community composition and diversity, in combination with the change of main physical and chemical properties of soil. Comprehensive analysis the impact on rhizosphere microenvironment of five kinds of plant root exduates. This study will reveal a process which plants through root secretion chemicals to affect the rhizosphere microbial community, then through the role of microbial physiological and biochemical to improve soil physical and chemical properties, and then improve their nutrition conditions. We will explore the physiological mechanism of plant species niche differentiation in the desert steppe community, and trying to screen the effective components by using the method of chemical simulate of root exudates, which can regulate rhizosphere microbial community and improve of soil characteristics. The results of this research will lay the theory foundation for restoration of soil environmental and restore the degraded grassland ecosystem.

根系分泌物是保持根际微环境活力与构成植物根际不同微生态特征的重要因素。本项目拟对内蒙古短花针茅荒漠草原群落中不同生态位5种植物根系分泌物的根际效应进行研究，并筛选出其有效组分。采用水培法提取植物根系分泌物，经气相色谱-质谱联用仪鉴定其组分与含量。在明确5种植物根系分泌物特性的前提下，采用化学试剂模拟根系分泌物组分。并将根系分泌物原液和组分模拟物回接草原土壤在室内培养后，重点采用高通量测序技术分析土壤中微生物群落组成及多样性，并结合土壤理化性状的变化，综合分析5种植物根系分泌物对根际微环境的影响。揭示植物通过根系分泌物影响根际微生物群落，进而通过微生物的生理生化作用改善土壤的理化性状，从而改善其营养条件；探究荒漠草原群落中物种生态位分化的生理机制；并试图通过化学模拟的方法筛选根系分泌物中能够调节根际微生物群落和改善土壤性状的有效组分，为修复土壤环境，恢复退化草地生态系统奠定基础。

本课题采用气相色谱-质谱联用仪（GC/MS）和超高液相色谱-四级杆飞行时间串联质谱法（UPLC-QTof/MS）分析了内蒙古荒漠草原群落中短花针茅、冷蒿、无芒隐子草、银灰旋花和阿尔泰狗娃花的根系分泌物组成。明确了5种植物的根系分泌物都包括酯类、烃类、酚类、酰胺类物质和少量的有机酸，其中酯类物质含量最高。5种植物有共同的根分泌物1,2-二甲苯和芥酸酰胺。挑选出5种植物根系分泌物中的11种组分进行化学模拟后处理土壤，采用Illumina Miseq高通量测序技术测定了土壤中的细菌和真菌的群落组成，并结合土壤主要性状的变化进行了综合分析。结果显示，1,2-二甲苯、芥酸酰胺和乙酰柠檬酸三丁酯均能改善土壤中的细菌群落并提高土壤的速效养分，有利于内蒙古荒漠草原植物适应其生存环境，特别是1,2-二甲苯的效果最好。结合5种植物的根系分泌物原液对土壤微生物群落和主要养分的影响分析，推测植物的根分泌物使土壤中Pseudomonas和Bacillus的丰度显著增加，导致了根际土壤中的养分活化，有助于提高植物自身适应环境的能力。因此，Pseudomonas和Bacillus是草原土壤中氮素和磷素有效化的关键微生物种，具有开发和应用潜力。综合上述结果，本研究为探讨植物体通过调节其根系分泌物组分而改善其根际土壤微环境的生理适应机制奠定了坚实的工作基础。同时为内蒙古荒漠草原根际促生菌的开发应用提供了重要的启示。项目资助发表核心论文4篇，已录用核心论文1篇，待发表论文2篇。培养硕士生1名，已获得硕士学位。