植物根系对根际微环境扰动机制研究进展

根际微环境是构建植物与土壤交流沟通的桥梁,也是植物遭受胁迫时优先作出响应的区域。植物根系作为根际的主要调控者,根构型和根系分泌物种类、数量的改变均可对根际微生物和土壤动物种群分布及其结构造成影响。然而,土壤动物的扰动、微生物的分解作用也可改善根际土壤特性,提高植物抗逆性及养分利用效率,从而促进植物根系生长。可见,植物根系-根际动物-根际微生物之间存在复杂的互作关系。本文从根际内、外微环境出发,分析了根际外植物根系对微环境的物理和化学扰动、根际内植物根系与微生物的互作扰动、根际内植物根系和土壤动物的物理扰动、以植物根系分泌物为介质的化学扰动等方面研究进展,在此基础上,论述了根际微环境主要影响因子之间的互作机制,并对该领域的研究方向进行了展望。     

根系分泌物介导的根际效应及在水体生态修复中的应用潜力

文章主要以根系分泌物为核心, 综述了根系分泌物的分类、发生机理及影响因素; 围绕着植物-土壤-微生物三者的关系, 阐述了根系分泌物介导的植物与植物之间的化感作用、植物与根际微生物之间的协同作用以及植物微生物相互作用对土壤物质循环的影响。水生植物以其生境的特殊性和功能的不可替代性, 对沉积物污染物去除和水体生态修复产生显著的影响。在水体生态问题较为严峻的今天, 充分认识水生植物根系分泌物介导的根际过程将为水生植物生态学和水体生态修复领域的发展提供基础, 并为学科应用潜力的开发提供依据。     

根系分泌物介导下植物-土壤-微生物互作关系研究进展与展望

根系分泌物是植物与土壤进行物质交换和信息传递的重要载体物质,是植物响应外界胁迫的重要途径,是构成植物不同根际微生态特征的关键因素,也是根际对话的主要调控者。根系分泌物对于生物地球化学循环、根际生态过程调控、植物生长发育等均具有重要功能,尤其是在调控根际微生态系统结构与功能方面发挥着重要作用,调节着植物-植物、植物-微生物、微生物-微生物间复杂的互作过程。植物化感作用、作物间套作、生物修复、生物入侵等都是现代农业生态学的研究热点,它们都涉及十分复杂的根际生物学过程。越来越多的研究表明,不论是同种植物还是不同种植物之间相互作用的正效应或是负效应,都是由根系分泌物介导下的植物与特异微生物共同作用的结果。近年来,随着现代生物技术的不断完善,有关土壤这一"黑箱"的研究方法与技术取得了长足的进步,尤其是各种宏组学技术(meta-omics technology),如环境宏基因组学、宏转录组学、宏蛋白组学、宏代谢组学等的问世,极大地推进了人们对土壤生物世界的认知,尤其是对植物地下部生物多样性和功能多样性的深层次剖析,根际生物学特性的研究成果被广泛运用于指导生产实践。深入系统地研究根系分泌物介导下的植物-土壤-微生物的相互作用方式与机理,对揭示土壤微生态系统功能、定向调控植物根际生物学过程、促进农业生产可持续发展等具有重要的指导意义。该文综述了根系分泌物的概念、组成及功能,论述了根系分泌物介导下植物与细菌、真菌、土壤动物群之间的密切关系,总结了探索根际生物学特性的各种研究技术及其优缺点,并对该领域未来的研究方向进行了展望。     

Advances and perspective in research on plant-soil-microbe interactions mediated by root exudates

根系分泌物是植物与土壤进行物质交换和信息传递的重要载体物质, 是植物响应外界胁迫的重要途径, 是构成植物不同根际微生态特征的关键因素, 也是根际对话的主要调控者。根系分泌物对于生物地球化学循环、根际生态过程调控、植物生长发育等均具有重要功能, 尤其是在调控根际微生态系统结构与功能方面发挥着重要作用, 调节着植物-植物、植物-微生物、微生物-微生物间复杂的互作过程。植物化感作用、作物间套作、生物修复、生物入侵等都是现代农业生态学的研究热点, 它们都涉及十分复杂的根际生物学过程。越来越多的研究表明, 不论是同种植物还是不同种植物之间相互作用的正效应或是负效应, 都是由根系分泌物介导下的植物与特异微生物共同作用的结果。近年来, 随着现代生物技术的不断完善, 有关土壤这一“黑箱”的研究方法与技术取得了长足的进步, 尤其是各种宏组学技术(meta-omics technology), 如环境宏基因组学、宏转录组学、宏蛋白组学、宏代谢组学等的问世, 极大地推进了人们对土壤生物世界的认知, 尤其是对植物地下部生物多样性和功能多样性的深层次剖析, 根际生物学特性的研究成果被广泛运用于指导生产实践。深入系统地研究根系分泌物介导下的植物-土壤-微生物的相互作用方式与机理, 对揭示土壤微生态系统功能、定向调控植物根际生物学过程、促进农业生产可持续发展等具有重要的指导意义。该文综述了根系分泌物的概念、组成及功能, 论述了根系分泌物介导下植物与细菌、真菌、土壤动物群之间的密切关系, 总结了探索根际生物学特性的各种研究技术及其优缺点, 并对该领域未来的研究方向进行了展望。     

连作障碍与根际微生态研究 Ⅰ. 根系分泌物及其生态效应

作物、蔬菜、果树以及苗木长期连作后,皆出现生长衰退和产量降低。许多研究结果表明,连作条件下土壤生态环境对植物生长有很大的影响,尤以植物残体与病原微生物的分解产物,对植物有致毒作用,并影响植物根系分泌物正常代谢,以致于发生自毒作用。本文围绕根系分泌物与根际微生态的相互关系,系统地介绍连作障碍条件下,影响根系分泌物的环境因素(土壤空气、湿度、养分与微生物)、活性物质(自身毒素、残体分解物、微生物产生毒素)、土壤病原菌等的根际效应,为深入研究根系分泌物与连作障碍的相互作用机制提供启示。     

连作障碍与根际微生态研究Ⅰ.根系分泌物及其生态效应

作物、蔬菜、果树以及苗木长期连作后,皆出现生长衰退和产量降低．许多研究结果表明,连作条件下土壤生态环境对植物生长有很大的影响,尤以植物残体与病原微生物的分解产物,对植物有致毒作用,并影响植物根系分泌物正常代谢,以致于发生自毒作用．本文围绕根系分泌物与根际微生态的相互关系,系统地介绍连作障碍条件下,影响根系分泌物的环境因素（土壤空气、湿度、养分与微生物）、活性物质（自身毒素、残体分解物、微生物产生毒素）、土壤病原菌等的根际效应,为深入研究根系分泌物与连作障碍的相互作用机制提供启示．     

植物根际微生物群落构建的研究进展

植物根际是指植物根系与土壤的交界面,是根系自身生命活动和代谢对土壤影响最直接、最强烈的区域,其物理、化学和生物性质不同于土体土壤。在这个区域里,与植物发生相互作用的大量微生物,被称为根际微生物。根际微生物在植物的生长发育和植物病虫害的生物防治等方面都具有十分重要的意义。本文总结了根际微生物群落构建的研究现状,介绍了根际微生物的经典和最新的研究方法,包括根箱法、同位素技术以及高通量测序、菌群定量分析、高通量分离培养等方法在根际微生物研究中的应用,讨论了植物根系分泌物(碳水化物、氨基酸、黄酮类、酚类、激素及其信号物质)和土壤物理化学性质对根际微生物群落的影响,概述了根际微生物-植物的互作机制,以及根际微生物群落对植物的促生作用、提高植物抗逆性和抑制作用,并对根际微生物群落研究中存在的问题和未来发展方向进行了展望。     

土壤环境下的根际微生物和植物互作关系研究进展

植物根系、土壤、根际微生物以及根际范围内其他因子等组成了根际微生态系统,在根际微生态系统中的不同组分之间存在着广泛的相互作用,其中以根系-土壤-微生物之间的相互作用网络最为复杂,同时也对整个根际系统的稳定和发展有着至关重要的影响。综述了近年来国内外对于土壤环境中根际互作关系研究的进展,探讨了土壤环境对植物和根际微生物群落的影响,植物如何调控根际微生物群落的组装和稳定过程,以及根际微生物对植物生长发育、病原菌防卫和抗逆性的调控作用等,分别从土壤环境、宿主植物和根际微生物三个层面,分析了它们在根际互作关系中的角色和作用机制,以期为农业生产和环境保护提供一定指导意义和借鉴作用。     

根系分泌物在重金属污染土壤生态修复中的作用机制研究进展

我国土壤重金属污染问题日益突出。作为一种绿色、安全的生物修复技术,植物修复技术备受关注。根系分泌物作为植物-土壤-微生物三者物质交换与信息传递的重要载体,是植物响应外界胁迫的重要生理生态指征,在植物修复过程中发挥关键作用。研究表明,根系分泌物能够有效调控根际微环境,提升植物抗逆能力,影响重金属在根际微域中的环境行为。传统的根际生态研究更多聚焦在养分调控等方面,而关于根系分泌物在污染场地生态修复中的作用机制研究相对较少。本文综述了根系分泌物对土壤理化性质、土壤微生物、植物生理代谢过程以及重金属在土壤-植物系统中迁移转化等方面的影响,系统总结了植物根系分泌物响应重金属胁迫的生理生态机制,并对未来土壤重金属污染生态修复研究方向进行了展望。     

植物根系分泌物主要生态功能研究进展

根系分泌物在植物根系-土壤-微生物互作过程及其生态反馈机制中发挥重要作用。在植物根际复杂网络互作过程中, 根系分泌物被认为是“根际对话”的媒介, 其在调控植物适应微生境、缓解根际养分竞争及构建根际微生物群落结构方面意义重大。该文结合国内外该领域主要研究成果, 综述了根系分泌物对植物生长、土壤微生物特性及土壤养分循环的影响, 并展望了未来根系分泌物的研究方向。     

Contributions of soil micro-fauna (protozoa and nematodes) to rhizosphere ecological functions

Contributions of soil micro-fauna (protozoa and nematodes) to rhizosphere ecological functions and possible modes of action were reviewed. Micro-fauna in rhizosphere play an important role in release of plant available nutrients, accumulation and stabilization of soil organic carbon, hormonal effects on roots, microbial diversity and functional stability, multi-trophic interactions above ground, and bioremediation of contaminated soils. Selective grazing, active dispersal and excretion by the micro-fauna not only benefit the rhizosphere ecological functions, but also have an impact on the whole soil and above-ground community. It appears that mechanically understanding rhizosphere ecological functions would remain incomplete without considering the interactions of micro-fauna with microorganisms and roots.     

New methods for new questions about rhizosphere/plant root interactions

Plant and Soil - In this opinion paper we review recent methodological developments underpinning the study of roots, the rhizosphere and interactions affecting soil functions, and explore new...     

Rhizosphere fauna: the functional and structural diversity of intimate interactions of soil fauna with plant roots

For decades, the term “rhizosphere fauna” has been used as a synonym to denote agricultural pests among root herbivores, mainly nematodes and insect larvae. We want to break with this constrictive view, since the connection between plants and rhizosphere fauna is far more complex than simply that of resource and consumer. For example, plant roots have been shown to be neither defenceless victims of root feeders, nor passive recipients of nutrients, but instead play a much more active role in defending themselves and in attracting beneficial soil microorganisms and soil fauna. Most importantly, significant indirect feed-backs exist between consumers of rhizosphere microorganisms and plant roots. In fact, the majority of soil invertebrates have been shown to rely profoundly on the carbon inputs from roots, breaking with the dogma of soil food webs being mainly fueled by plant litter input from aboveground. In this review we will highlight areas of recent exciting progress and point out the black boxes that still need to be illuminated by rhizosphere zoologists and ecologists.     

The role of root exudates and allelochemicals in the rhizosphere

Plant roots serve a multitude of functions in the plant including anchorage, provision of nutrients and water, and production of exudates with growth regulatory properties. The root–soil interface, or rhizosphere, is the site of greatest activity within the soil matrix. Within this matrix, roots affect soil structure, aeration and biological activity as they are the major source of organic inputs into the rhizosphere, and are also responsible for depletion of large supplies of inorganic compounds. Roots are very complicated morphologically and physiologically, and their metabolites are often released in large quantities into the soil rhizosphere from living root hairs or fibrous root systems. Root exudates containing root-specific metabolites have critical ecological impacts on soil macro and microbiota as well as on the whole plant itself. Through the exudation of a wide variety of compounds, roots impact the soil microbial community in their immediate vicinity, influence resistance to pests, support beneficial symbioses, alter the chemical and physical properties of the soil, and inhibit the growth of competing plant species. In this review, we outline recent research on root exudation and the role of allelochemicals in the rhizosphere by studying the case of three plants that have been shown to produce allelopathic root exudates: black walnut, wheat and sorghum     

施用污泥对油菜根际养分和不同种类重金属的影响

根际是控制植物养分动态的重要因素,养分动态也影响着根际土壤环境。当土壤被污水污泥改良后,根际土壤中的养分和重金属性质也会发生变化。目前很少有人研究施用污泥的土壤中植物根系对根际重金属有效性和分布的影响。采用根垫—冰冻薄层切片法对施用污泥后土壤中油菜根际的养分和重金属分布情况进行研究,以期探明污泥改良土壤中根际重金属的活化特征。当土壤施用污泥后,根际土壤中DTPA提取态Zn,Cd,Ni,Mn,有效磷,有效钾和铵态氮被显著消耗,而根际土壤中DTPA提取态Cu没有明显的消耗或积累。当土壤中施用大量污泥时,根际土壤的pH值随着离根表面距离的增加而增加。无论土壤是否用污泥处理,油菜根际土壤中可交换态Cu都显著减少。当土壤被50%污泥改良时,在距离根表面0—2 mm处的油菜根际土壤中碳酸盐结合态,铁锰氧化物结合态,有机物结合态,残渣态的Cu和Zn都被消耗较多。污泥的施用对油菜的生长有促进作用。随着污泥施用量的增加,油菜地上部分Cu和Zn的含量没有显著变化。施用污泥量小于25%的土壤中,污泥没有增加重金属的可利用性和移动性。除了Cu,油菜根际土壤中DTPA提取态Zn,Cd,Ni的减少表明施用污泥的土壤中重金属的活化是非常有限的。     

Root exudates and their ecological consequences in forest ecosystems: Problems and perspective

植物根际过程与调控机理研究已成为当前土壤学最活跃、最敏感的研究领域, 而根系分泌物作为根系-土壤-微生物界面物质能量交换和信息传递的重要媒介物质, 是构成根际微生态系统活力与功能特征的内在驱动因素, 是根际概念与根际过程存在的重要前提和基础。然而, 由于传统的根际过程研究更强调以实际生产问题为导向, 加之农作物生长周期较短、操作便利等诸多因素, 以往对植物根系分泌物研究主要聚焦在农业生态系统, 而有关根系分泌物在森林生态系统中的重要作用与调控机理研究甚少, 认识相对零散和片段化。基于此, 该文结合作者实际研究工作中的主要成果和该领域国际前沿动态, 综述了森林根系分泌物的生态重要性, 重点论述了目前森林根系分泌物生态学研究中存在的主要问题与不足, 在此基础上展望了未来森林根系分泌物生态学研究中值得关注的重点方向和研究内容。     

Plant metabolomics for plant chemical responses to belowground community change by climate change

General circulation models on global climate change predict increase in surface air temperature and changes in precipitation. Increases in air temperature (thus soil temperature) and altered precipitation are known to affect the species composition and function of soil microbial communities. Plant roots interact with diverse soil organisms such as bacteria, protozoa, fungi, nematodes, annelids and insects. Soil organisms show diverse interactions with plants (eg. competition, mutualism and parasitism) that may alter plant metabolism. Besides plant roots, various soil microbes such as bacteria and fungi can produce volatile organic compounds (VOCs), which can serve as infochemicals among soil organisms and plant roots. While the effects of climate change are likely to alter both soil communities and plant metabolism, it is equally probable that these changes will have cascading consequnces for grazers and subsequent food web components aboveground. Advances in plant metabolomics have made it possibile to track changes in plant metabolomes as they respond to biotic and abiotic environmental changes. Recent developments in analytical instrumentation and bioinformatics software have established metabolomics as an important research tool for studying ecological interactions between plants and other organisms. In this review, we will first summarize recent progress in plant metabolomics methodology and subsequently review recent studies of interactions between plants and soil organisms in relation to climate change issues.     

Rates of root and organism growth, soil conditions, and temporal and spatial development of the rhizosphere

BACKGROUND: Roots growing in soil encounter physical, chemical and biological environments that influence their rhizospheres and affect plant growth. Exudates from roots can stimulate or inhibit soil organisms that may release nutrients, infect the root, or modify plant growth via signals. These rhizosphere processes are poorly understood in field conditions. SCOPE AND AIMS: We characterize roots and their rhizospheres and rates of growth in units of distance and time so that interactions with soil organisms can be better understood in field conditions. We review: (1) distances between components of the soil, including dead roots remnant from previous plants, and the distances between new roots, their rhizospheres and soil components; (2) characteristic times (distance(2)/diffusivity) for solutes to travel distances between roots and responsive soil organisms; (3) rates of movement and growth of soil organisms; (4) rates of extension of roots, and how these relate to the rates of anatomical and biochemical ageing of root tissues and the development of the rhizosphere within the soil profile; and (5) numbers of micro-organisms in the rhizosphere and the dependence on the site of attachment to the growing tip. We consider temporal and spatial variation within the rhizosphere to understand the distribution of bacteria and fungi on roots in hard, unploughed soil, and the activities of organisms in the overlapping rhizospheres of living and dead roots clustered in gaps in most field soils. CONCLUSIONS: Rhizosphere distances, characteristic times for solute diffusion, and rates of root and organism growth must be considered to understand rhizosphere development. Many values used in our analysis were estimates. The paucity of reliable data underlines the rudimentary state of our knowledge of root-organism interactions in the field.     

Bidirectional plant‐mediated interactions between rhizobacteria and shoot‐feeding herbivorous insects: a community ecology perspective

1. Plants interact with various organisms, aboveground as well as belowground. Such interactions result in changes in plant traits with consequences for members of the plant‐associated community at different trophic levels. Research thus far focussed on interactions of plants with individual species. However, studying such interactions in a community context is needed to gain a better understanding.
2. Members of the aboveground insect community induce defences that systemically influence plant interactions with herbivorous as well as carnivorous insects. Plant roots are associated with a community of plant‐growth promoting rhizobacteria (PGPR). This PGPR community modulates insect‐induced defences of plants. Thus, PGPR and insects interact indirectly via plant‐mediated interactions.
3. Such plant‐mediated interactions between belowground PGPR and aboveground insects have usually been addressed unidirectionally from belowground to aboveground. Here, we take a bidirectional approach to these cross‐compartment plant‐mediated interactions.
4. Recent studies show that upon aboveground attack by insect herbivores, plants may recruit rhizobacteria that enhance plant defence against the attackers. This rearranging of the PGPR community in the rhizosphere has consequences for members of the aboveground insect community. This review focusses on the bidirectional nature of plant‐mediated interactions between the PGPR and insect communities associated with plants, including (a) effects of beneficial rhizobacteria via modification of plant defence traits on insects and (b) effects of plant defence against insects on the PGPR community in the rhizosphere. We discuss how such knowledge can be used in the development of sustainable crop‐protection strategies.