AM真菌在植物病虫害生物防治中的作用机制

丛枝菌根(Arbuscular Mycorrhizae,AM)真菌是一类广泛分布于土壤生态系统中的有益微生物,能与大约80%的陆生高等植物形成共生体。由土传病原物侵染引起的土传病害被植物病理学界认定为最难防治的病害之一。研究表明,AM真菌能够拮抗由真菌、线虫、细菌等病原体引起的土传性植物病害,诱导宿主植物增强对病虫害的耐/抗病性。当前,利用AM真菌开展病虫害的生物防治已经引起生态学家和植物病理学家的广泛关注。基于此,围绕AM真菌在植物病虫害生物防治中的最新研究进展,从AM真菌改变植物根系形态结构、调节次生代谢产物的合成、改善植物根际微环境、与病原微生物直接竞争入侵位点和营养分配、诱导植株体内抗病防御体系的形成等角度,探究AM真菌在植物病虫害防治中的作用机理,以期为利用AM真菌开展植物病虫害的生物防治提供理论依据,并对本领域未来的发展方向和应用前景进行展望。     

丛枝菌根对有机污染土壤的修复作用及机理

丛枝菌根(AM)是丛枝菌根真菌(AMF)与植物根系相互作用的互惠共生体,能改良土壤结构,增强植物抗性.自然界中已知的AMF有170多种,分布广泛,且可与大多数植物共生.利用AM修复有机污染土壤正成为一个崭新的研究方向.本文综述了AM对多环芳烃、酞酸脂、石油和农药等一些典型有机污染物污染土壤的修复作用.AM修复有机污染土壤的机理主要包括:AMF代谢有机污染物;AM分泌酶,降解污染物;AM影响根系分泌作用,并促进根际微生物对有机污染物的降解;AMF宿主植物吸收积累污染物.AM修复研究中,高效AMF的筛选、复合菌种效应、土壤老化、AM作用下植物对有机污染物的吸收积累等几方面仍有待于深入研究.     

丛枝菌根结构与功能研究进展

丛枝菌根(arbuscular mycorrhiza,AM)是陆地生态系统中分布最广泛、最重要的互惠共生体之一,对提高植物抗逆性、修复污染生境、保持生态系统稳定与可持续生产力的作用显著.AM结构特征是判断菌根形成的主要指标,与其功能密切相关.本文总结了AM丛枝结构、泡囊结构、菌丝结构和侵入点结构等发育特征;分析了A型丛枝结构、P型丛枝结构、泡囊结构和根外菌丝结构与促进寄主植物养分吸收和生长、提高植物抗旱性、耐涝性、耐盐性、抗高温、拮抗病原物、提高植物抗病性、抗重金属毒性、分解有毒有机物、修复污染与退化土壤等功能的关系,及其所发挥的重要作用;探讨了影响AM结构与功能的因子,以及基于AM不同结构所发挥功能的作用机制.旨在为系统研究AM真菌发育特征、AM真菌效能机制,以及评价和筛选AM真菌高效菌种提供依据.     

同位素示踪技术在丛枝菌根真菌生态学研究中的应用

丛枝菌根(arbuscular mycorrhizal,AM)真菌是生态系统中重要的土壤微生物之一。AM真菌菌丝体网络是由AM真菌菌丝体在土壤生态系统中连接两株或两株以上植物根系所形成的菌丝体网络。随着菌根学研究的深入,如何直观的揭示AM真菌的生态学功能已经成为相关领域关注的热点问题。研究发现,利用同位素示踪技术可以开展AM真菌与宿主植物对土壤矿质营养的吸收、转运等方面的研究,以及菌丝体网络对不同宿主植物之间营养物质的分配研究和AM真菌在生态系统生态学中的功能研究。基于此,为了阐明同位素示踪技术在AM真菌研究中的价值,围绕菌根学最新研究进展,系统回顾了利用同位素示踪技术探究AM共生体对不同元素吸收和转运的机制、同位素示踪技术在AM真菌菌丝体网络研究中的价值和利用同位素示踪技术研究AM真菌在生态系统中的功能,为AM真菌生态学功能的研究提供理论基础,并对本领域未来的研究方向和应用前景进行展望。     

根瘤菌-豆科植物共生体系在重金属污染环境修复中的地位、应用及潜力

土壤重金属污染严重影响了人类健康和生态系统稳定,已成为亟待解决的现实问题。在重金属污染地,氮素的极端不足是植被恢复主要限制因子之一。根瘤菌-豆科植物共生体系是固氮能力最强的生物固氮体系,在促进重金属污染地氮素循化和营养元素积累中具有重要作用。本文阐述土壤重金属污染的修复方法及其特点,微生物抗重金属的机理及促植物生长和重金属积累的特性,根瘤菌-豆科植物共生体系在土壤重金属污染修复中的优越性,研究现状及应用潜力。提出应用"豆科植物-根瘤菌共生体系"修复重金属污染土壤的新思路和新任务。     

溶磷微生物在钝化和植物修复重金属污染土壤中的作用

钝化和植物修复是重金属污染土壤修复的重要技术手段,而溶磷微生物可进一步增强钝化和植物修复重金属污染土壤的作用。介绍了钝化和植物修复重金属污染土壤的基本原理,总结了溶磷微生物对土壤中难溶性磷酸盐的溶解、利用磷酸盐钝化修复重金属污染土壤、溶磷微生物对磷酸盐钝化修复的强化以及溶磷微生物强化植物修复重金属污染土壤的研究进展,探讨了溶磷微生物对重金属的抗性及其溶磷机理、溶磷微生物对磷酸盐钝化修复重金属污染土壤的强化作用机理以及溶磷微生物强化植物修复重金属污染土壤的作用机理。旨在为生物修复重金属污染土壤研究提供一定的理论依据和技术支撑。     

重金属污染土壤中生物间相互作用及其协同修复应用

土壤是人类赖以生存的物质基础。我国土壤重金属污染状况不容乐观,给人类健康构成严重威胁。生物修复重金属污染土壤被广泛认为是可持续的修复技术,但当前仍存在修复效率不高的科学瓶颈问题。土壤中生活着丰富的微生物、植物和动物,且这些生物之间存在着复杂的相互作用,并且通过物质循环和能量传递形成了错综复杂的食物网联系。土壤生物间的相互作用能深刻影响土壤中污染物的迁移转化和生物修复的效率,多元生物协同的修复技术集合了单一生物修复方法的优势,具有强化生物修复效果的巨大潜力。文中综述了土壤中微生物-植物-动物之间的相互作用,及其对土壤重金属迁移转化和生物修复效果的影响,并对定向调控土壤食物网结构、提高重金属污染土壤的生物修复效果、建立基于食物网的多元生物协同修复技术进行了展望。     

印度梨形孢-植物共生关系的建立及共生体对重金属胁迫的响应

重金属污染土壤的治理一直是全球热点问题,植物-微生物联合修复技术因其高效、经济和减少二次污染而被广泛关注.印度梨形孢是一种能够与植物共生的真菌,它能够通过与植物建立共生关系的方式来提高宿主植物的生长和耐胁迫能力.本文系统总结了印度梨形孢-植物体共生关系的建立过程,以及重金属胁迫下共生体的生长、光合作用、抗性生理指标、防御基因表达和对重金属富集等响应的研究进展,并针对研究现状提出了展望.文章对深入了解利用印度梨形孢与植物共生体对重金属污染土壤的修复提供了理论参考.     

土壤重金属生物毒性研究进展

世界范围内土壤重金属污染不断加重,由污染所带来的问题以及如何治理污染已经受到人们越来越多的关注.土壤重金属将对土壤生物产生影响,而土壤生物在重金属的胁迫下也会产生不同的响应.综述了国内外近年来土壤重金属生物毒性的研究进展,介绍了土壤重金属污染对陆地生态系统中植物、动物和微生物生长的影响;土壤重金属生物毒性的影响因素;土壤重金属生物毒性的研究方法;土壤重金属生物毒性的预测模型,最后提出了问题和展望.     

环境污染物对丛枝菌根(AM)形成及功能的影响

丛枝菌根(AM)具有植物和微生物的双重特性,在污染土壤修复中受到越来越多的重视.AM在修复污染土壤的同时,也深受污染物毒害的影响,从而降低AM在污染土壤修复中的作用.如何减少环境污染物对AM的不利影响,是AM应用中需要考虑的问题.从有机和无机污染物角度, 综述了不同污染物对AM形成及功能的影响,并分析了可能的影响机理.大量研究表明,无论是有机污染物还是无机污染物,都会对AM的结构、形成和功能产生破坏性影响,主要表现在孢子萌发、侵染率、菌丝伸长受抑制等.有机污染物可能通过影响光合产物向AM真菌的分配, 间接影响AM真菌的活性,而重金属则通过抑制AM真菌活性, 直接对其产生影响.     

Effect of heavy metal pollution on mycorrhizal colonization and function: physiological, ecological and applied aspects

 High concentrations of heavy metals in soil have an adverse effect on micro-organisms and microbial processes. Among soil microorganisms, mycorrhizal fungi are the only ones providing a direct link between soil and roots, and can therefore be of great importance in heavy metal availability and toxicity to plants. This review discusses various aspects of the interactions between heavy metals and mycorrhizal fungi, including the effects of heavy metals on the occurrence of mycorrhizal fungi, heavy metal tolerance in these micro-organisms, and their effect on metal uptake and transfer to plants. Mechanisms involved in metal tolerance, uptake and accumulation by mycorrhizal hyphae and by endo- or ectomycorrhizae are covered. The possible use of mycorrhizal fungi as bioremediation agents in polluted soils or as bioindicators of pollution is also discussed. Accepted: 23 June 1997     

Feasible Bioremediation through Arbuscular Mycorrhizal Fungi Imparting Heavy Metal Tolerance: A Retrospective

Bioremediation is an integrated management of a polluted ecosystem where different organisms are employed to catalyze the natural processes that decontaminate the environment. The potential role of bioremediation, particularly higher terrestrial plants (phytoremediation) research in the remediation of metal-polluted sites, has been the focus of much research in recent years. Arbuscular mycorrhizal fungi are soil microorganisms that establish mutual symbiosis with the majority of higher plants, providing direct links between fungi and roots. This paper reviews the incidence of arbuscular mycorrhizal fungi in metal polluted sites, their role in imparting metal tolerance to plants, the factors affecting arbuscular mycorrhizal fungi in metal polluted sites, and their mechanism of heavy metal tolerance. Particular attention is given to the current methodologies and challenges in this field.     

丛枝菌根在植物修复重金属污染土壤中的作用

丛枝菌根（Arbuscular mycorrhizae，AM）是自然界中分布最广的一类菌根，AM真菌能与陆地上绝大多数的高等植物共生，常见于包括重金属污染土壤在内的各种生境中。在重金属污染条件下，AM真菌可以减轻重金属对植物的毒害，影响植物对重金属的吸收和转运，在重金属污染土壤的植物修复中显示出极大的应用潜力。重点介绍了AM真菌对植物重金属耐性的影响及其在植物提取和植物稳定中的应用等方面的进展，讨论了未来研究所面临的任务和挑战。     

Arbuscular mycorrhiza can depress translocation of zinc to shoots of host plants in soils moderately polluted with zinc

There is increasing and widespread interest in the maintenance of soil quality and remediation strategies for management of soils contaminated with organic pollutants and trace metals or metalloids. There is also a growing body of evidence that arbuscular mycorrhizal (AM) fungi can exert protective effects on host plants under conditions of soil metal contamination. Research has focused on the mechanisms involved and has raised the prospect of utilizing the mutualistic association in soil re-vegetation programmes. In this short paper we briefly review this research, summarize some recent work and highlight some new data which indicate that the alleviation of metal phytotoxicity, particularly Zn toxicity, by arbuscular mycorrhiza may occur by both direct and indirect mechanisms. Binding of metals in mycorrhizal structures and immobilization of metals in the mycorrhizosphere may contribute to the direct effects. Indirect effects may include the mycorrhizal contribution to balanced plant mineral nutrition, especially P nutrition, leading to increased plant growth and enhanced metal tolerance. Further research on the potential application of arbuscular mycorrhiza in the bioremediation or management of metal-contaminated soils is also discussed.     

Hyperaccumulators, arbuscular mycorrhizal fungi and stress of heavy metals

Use of plants, with hyperaccumulating ability or in association with soil microbes including the symbiotic fungi, arbuscular mycorrhiza (AM), are among the most common biological methods of treating heavy metals in soil. Both hyperaccumulating plants and AM fungi have some unique abilities, which make them suitable to treat heavy metals. Hyperaccumulator plants have some genes, being expressed at the time of heavy metal pollution, and can accordingly localize high concentration of heavy metals to their tissues, without showing the toxicity symptoms. A key solution to the issue of heavy metal pollution may be the proper integration of hyperaccumulator plants and AM fungi. The interactions between the soil microbes and the host plant can also be important for the treatment of soils polluted with heavy metals.     

A new dawn – the ecological genetics of mycorrhizal fungi

Many human activities, such as ore mining and smeltering, sewage sludge treatment and fossil fuel consumption, result in toxic soil concentrations of 'heavy metals' (Al, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ti, Zn and others) (Gadd, 1993). There are also natural soils, such as serpentine, with levels of heavy metals that inhibit or preclude the growth of many plants and soil micro-organisms. However, certain plants and microorganisms do grow in these metalliferous sites. Understanding the physiology, ecology and evolution of tolerance to elevated soil metal concentrations is important in an applied setting, and is also of interest in theoretical biology. Applied importance relates to the improvement of forest health in areas subject to increasing pollution, rehabilitation of severely polluted sites by phytostabilization of metals, and metal removal using hyperaccumulating plants (Krämer, 2000; Ernst, 2000). Areas of theoretical interest include the evolution of local adaptation (Sork et al ., 1993) and how it is shaped by the combined influences of natural selection, gene flow and genetic architecture, as well as metal influences on various species interactions (Pollard, 2000). A paper appears on pages 367–379 in this issue by Jan Colpaert and coworkers which adroitly combines the disparate fields of physiology, genetics and ecology to answer several outstanding questions concerning heavy metal tolerance in mycorrhizal fungi.
Mycorrhizal fungi, which interact mutualistically with the majority of plant species, are well known for improving the P status of their hosts (Smith & Read, 1997). Some mycorrhizal fungi are also able to mobilize N and P from organic substrates and to provide plants with improved micronutrient and water acquisition, pathogen resistance, and a variety of other benefits (Smith & Read, 1997). One of these additional benefits is the amelioration of toxicity in metalliferous soils.     

有机污染土壤中菌根的作用

近年来,土壤有机污染问题日益突出,传统的修复方法存在局限性。菌根是植物根系与菌根真菌形成的共生体,能增强植物的逆境抗胁迫能力,对于促进有机污染物的降解和转化具有积极的作用。本文主要阐述了石油、多环芳烃、多氯联苯、农药和酞酸酯等几类典型的有机污染土壤中外生菌根和丛枝菌根的作用;旨在说明利用菌根技术修复有机污染土壤是生物修复的一项重要工具,具有广阔的发展前景,为进一步研究菌根的作用以及更好地运用菌根技术奠定基础。     

Role of soil microbes in the rhizospheres of plants growing on trace metal contaminated soils in phytoremediation

This article reviews recent developments in in situ bioremediation of trace metal contaminated soils, with particular reference to the microbial dynamics in the rhizospheres of plants growing on such soils and their significance in phytoremediation. In non-agricultural conditions, the natural role of plant growth promoting rhizobacteria (PGPR), P-solubilizing bacteria, mycorrhizal-helping bacteria (MHB) and arbuscular mycorrhizal fungi (AMF) in maintaining soil fertility is more important than in conventional agriculture, horticulture, and forestry where higher use of agrochemicals minimize their significance. These microbes initiate a concerted action when a particular population density is achieved, i.e. quorum sensing. AMF also recognize their host by signals released by host roots, allowing a functional symbiosis. AM fungi produce an insoluble glycoprotein, glomalin, which sequester trace elements and it should be considered for biostabilization leading to remediation of contaminated soils. Conclusions drawn from studies of metal uptake kinetics in solution cultures may not be valid for more complex field conditions and use of some combination of glasshouse and field experiments with organisms that occur within the same plant community is suggested. Phytoextraction strategies, such as inoculation of plants to be used for phytoremediation with appropriate heavy metal adapted rhizobial microflora, co-cropping system involving a non-mycorrhizal hyperaccumulator plant and a non-accumulator but mycorrhizal with appropriate AMF, or pre-cropping with mycotrophic crop systems to optimize phytoremediation processes, merit further field level investigations. There is also a need to improve our understanding of the mechanisms involved in transfer and mobilization of trace elements by rhizosphere microbiota and to conduct research on selection of microbial isolates from rhizosphere of plants growing on heavy metal contaminated soils for specific restoration programmes. This is necessary if we are to improve the chances of successful phytoremediation.