Ectomycorrhizae

10 Key excerpts on "Ectomycorrhizae"

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  Handbook of Microbial Biofertilizers

  • Mahendra Rai(Author)
  • 2006(Publication Date)
  • CRC Press

    (Publisher)

  Chapter 10 Role of Mycorrhizae in Forestry Role of Mycorrhizae in Forestry Hanna Dahm INTRODUCTION Mycorrhiza is the result of a plant-microbial interaction in the soil of great ecological significance. Mycorrhizae are formed by association be-tween a plant root and a fungus, and by far the majority of vascular plants are involved in these associations. There are a number of different forms of mycorrhizal association, but in many cases the fungus involved (the myco-biont) enhances plant uptake of nutrients from the soil, increases rootlet size and longevity, protects the root system from many pathogens, and can also absorb and translocate water to the plant host (Killham, 1994). The mechanism of enhanced nutrient uptake by mycorrhizal plants is the increased soil volume exploited by the extramatrical mycelium of the my-corrhizal fungus. Nutrients can therefore be transported from beyond the narrow nutrient depletion zone that surrounds the nonmycorrhizal roots. In addition to the mycorrhizal fungus exploiting the greater soil volume, the fungal mycelium can often absorb nutrients at lower solution concentra-tions than can the uninfected plant root. The mycorrhizal association can also enable the plant host to access nu-trients (particularly nitrogen) in an organic form that would otherwise be unavailable. In addition, some mycorrhizal plants can be connected via hyphal strands and this link provides a means of nutrient transfer from plant to plant (Killham,1994). ECOLOGICAL SIGNIFICANCE OF MYCORRHIZAE Most land plants form mycorrhizae. Many species of fungi are involved in ectomycorrhizal associations: of a forest, a single tree species, an indi-vidual tree, or even a small segment of lateral root. Even a single tree species 241 can have numerous species of fungi capable of forming Ectomycorrhizae on its roots; a single fungus can enter into ectomycorrhizal association with numerous tree species.

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  Ectomycorrhizae

  Their Ecology and Physiology

  • G.C. Marks(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  In I. Structure, Morphogenesis, and Ultrastructure 13 broadest terms, there are three classes, the Ectomycorrhizae, ectendo-mycorrhizae, and endomycorrhizae. Two other types may be included but their niche in the classification system is disputed. These are the peritrophic associations and pseudomycorrhizae. It appears that there is some doubt as to the immutability of these groups. Laiho (1967) ob-served that young seedlings produced ectendomycorrhizae but when transplanted into the field the new associations were Ectomycorrhizae. An even more disturbing aspect of these associations was illustrated by Marks et al. (1967) when they demonstrated that intracellular penetra-tion of cortical cells (i.e., the ectendomycorrhizal condition) was com-mon in aging mycorrhizae. Until further information on mycorrhizal development is forthcoming, these groupings must be considered arbi-trary, although it appears they may reflect the host/fungal relationships that exist. A. PERITROPHIC ASSOCIATIONS The term, peritrophic association, was coined by Jahn (1934) to describe fungi found on root surfaces. These include saprophytes, po-tential parasites, and mycorrhiza formers. It is possible that in the initial stages of mycorrhizal formation the thin weft of hyphae formed on the root surface prior to Hartig net formation could represent a special type of relationship between fungus and root. Foster and Marks (1967) found that a variety of fungal and bacterial forms can be seen closely asso-ciated with the outer hyphae of the mycorrhizal mantle. These asso-ciations could have special significance in mobilization of nutrients and nutrient absorption by roots. B. Ectomycorrhizae These represent one of the commonest forms of mycorrhizal associa-tion encountered and are the dominant forms in most forest trees. The fungus forms a mantle of hyphae covering the slow-growing, unsuberized parts of the roots, and it penetrates, intercellularly, to varying depths, into the host cortex.

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  Advances in Biological Science Research

  A Practical Approach

  • Surya Nandan Meena, Milind Naik(Authors)
  • 2019(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 19

  Advances in methods and practices of ectomycorrhizal research

  Lakshangy S. Charya, and Sandeep Garg      Department of Microbiology, Goa University, Taleigao Plateau, Goa, India

  Abstract

  Ectomycorrhiza (ECM) is a symbiotic association of fungi with the feeder roots of higher plants in which both the partners are mutually benefited and indeed the association appears to be significant for the existence of both the partners. The majority of ECM synthesizing fungi belong to the classes Basidiomycetes and Ascomycetes that form fruiting bodies like mushrooms, puffballs, coral fungi, toadstools, truffles, etc. Though the benefits offered by ectomycorrhizal fungi are extensive, they are very sensitive. The vegetative mycelium is fragile and needs to be handled with suitable techniques and utmost care. The conventional methods of fungal isolation and cultivation are central to handling ECM fungi. The scientific community in the field of ECM research has contributed immensely toward advancement in methodologies or the techniques employed. The variations could be the simpler basic methods like the subculturing methods, the design of culture media, formulations of fungal inoculum, methods assessing mycorrhizae, to more advanced methods that range from arrays of molecular techniques like PCR, RFLP, DGGE, and temperature gradient gel electrophoresis to transcriptomic and proteomic analysis. Ectomycorrhizal fungi are not only applicable as bioinoculants but also form an important source of biological pigments, antibiotic compounds, and edible mushrooms with the known fact that they are nutritionally enriched. The methods described in this chapter provide detailed knowledge and enhanced applicability of ECM association for sustainable development.

  Keywords

  Advances; Applications; Ectomycorrhizal fungi; Methodology; Molecular tools

  19.1. Introduction

  Ectomycorrhizae (ECM), also termed as ectotrophic mycorrhizae, are the second most predominant type of mycorrhiza found in nature. A typical ectomycorrhizal root shows formation of characteristic features such as “mantle” and “hartig net.” The fungal mantle, also known as the “sheath,” is the clustering of fungal mycelia on the surface of the host root and the hartig net is the network of fungal hyphae formed between the epidermal or cortical cells of the host root without penetrating the root cells. From the mantle surface arise “rhizomorphs” that are hyphal strands interwoven to form bundles and these structures spread in the surrounding soil. In tropical forests, rhizomorph development can be prolific, sometimes traveling several meters away from the host root [1 ,2

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  Microbial Biodiversity in Sustainable Agriculture

  • Chandra, Ram(Authors)
  • 2021(Publication Date)
  • Daya Publishing House

    (Publisher)

  Frank in 1885, and originates from the Greek mycos , This ebook is exclusively for this university only. Cannot be resold/distributed. meaning ‘fungus’ and rhiza , meaning ‘root’. Mycorrhiza is a symbiotic mutualistic relationship between special soil fungi and fine plant roots; it is neither the fungus nor the root, but rather the structure formed from these two partners. Since the association is mutualistic, both organisms benefit from the association. The fungus receives carbohydrates (sugars) and growth factors from the the plant, which in turn receives many benefits, including increased nutrient absorption. In this association, the fungus takes over the role of the plant’s root hairs and acts as an extension of the root system. Among important plants that associate with mycorrhizal fungi are corn, carrots, leek, potatoes, beans, soybeans, other legumes, tomatoes, peppers, onions, garlic, sunflower, strawberries, citrus, apples, peaches, grapes, cotton, coffee, tea, cocoa, sugarcane, forest species, wild plants, and even weeds. Cruciferae in general, and some aquatic plants are usually non-mycorrhizal. Mycorrhizal Types On the basis of tropic level two main types of mycorrhizae may be found, depending on whether the fungus penetrates into the root cells or not: Ectomycorrhizae and endomycorrhizae . Ectotrophic types, or e ctomycorrhizae , are found in roots of trees such as pines, birches, willows, and oaks. This type causes a drastic change in the root shape. The ectomycorrhizal fungus penetrates between the cell walls of the cortex and forms a covering sheath, or mantle, of fungal hyphae around the entire root. Ectomycorrhizae are short and forked and sometimes appear as tight clusters. Most ectomycorrhizal fungi produce mushrooms and can be cultivated in culture media in the laboratory. Endotrophic types, endomycorrhizae or Arbuscular Mycorrhizae (AM) do not form a mantle over the root, and the fungus actually enters the cortex cells.

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  Metals in the Environment

  Analysis by Biodiversity

  • M.N.V. Prasad(Author)
  • 2001(Publication Date)
  • CRC Press

    (Publisher)

  2 Mycorrhizal Fungi Jan V. Colpaert Limburgs Universitair Centrum, Diepenbeek, Belgium P. Vandenkoornhuyse Universite de Lille, Paris, France 1 INTRODUCTION Mycorrhizal symbiosis is the most widespread symbiosis between plants and mi­ croorganisms. Between 80% and 90% of all seed plant species have fungi in their roots, forming structures known as mycorrhizas (1). Mycorrhizas are a functional part of the plant roots where the fungus provides an interface between the roots and the soil. Mycorrhizas are very effective in assimilating nutrients, including essential metals and their analogues, many of which are present in toxic concen­ trations on contaminated soils. Mycorrhizas range widely in form and in type of fungus involved, demonstrating that they represent not a single class of symbiosis but rather a type of plant-fungus association that has evolved repeatedly, in re­ sponse to distinct selection pressures (2). Mycorrhizas have been classified in various ways, such as into ectomycorrhizas, typically formed between some long- lived woody plant species and long-lived fungi (generally Basidiomycota and Ascomycota) (Fig. 1), and endomycorrhizas. The latter contain the most ubiqui­ tous mycorrhizal association, the arbuscular mycorrhizas (Fig. 1), involving a 37 38 Colpaert and Vandenkoornhuyse F ig . 1 Longitudinal section of an ectomycorrhiza and an arbuscular mycor-rhiza. (Ref. 105.) very wide range of plants and a small group of fungi in the Glomales (Zygomy- cota) (3). A much smaller group of plants form the ericoid endomycorrhizas. In the following paragraphs, we describe the three types of mycorrhizas that are commonly found in metal-polluted habitats. Arbuscular mycorrhizal (AM) fungi are strict biotrophs. In exchange for carbon compounds, these symbiotic fungi improve the uptake of phosphorus in plants (1,4,5), a highly immobile element in soil.

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  Performance of forest trees and mycorrhizas in response to varying nutrients

  • (Author)
  • 2016(Publication Date)
  • Cuvillier Verlag

    (Publisher)

  17 CHAPTER 1. General introduction Dieses Werk ist copyrightgeschützt und darf in keiner Form vervielfältigt werden noch an Dritte weitergegeben werden. Es g ilt nur für den persönlichen Gebrauch. CHAPTER 1. General introduction 18 1. General introduction 1.1. Description of mycorrhizal symbiosis In temperate forests, one of the most common mutualistic symbioses is formed by association of tree root tips with mycorrhizal fungi forming mycorrhiza. Mycorrhizas are important for plant nutrient uptake (Tuomi et al. , 2001). The mycorrhizal symbiosis is a trading system, in which the mycorrhizal fungi through their external hyphal network take up and deliver nutrients to the host plant, in return, they obtain from the plant the carbohydrates they need for essential organic compound synthesis (Smith & Read, 2008). Mycorrhizas increase the surface for nutrient uptake and overcome the nutrient-depletion area around roots for immobile nutrients (Agerer 2001). They connect nutrient fluxes between trees and soil and contribute significantly to plant phosphorous (P) and nitrogen (N) supply (van der Heijden et al. , 1988). Since forest trees have about 100% of the root tips colonized by mycorrhizal fungi (Lang et al. , 2011; Lang & Polle, 2011), almost all N and P present in plants has been taken up via mycorrhizas (van der Heijden et al. , 1988; Högberg et al. , 2006; Lambers et al. , 2009). Therefore, mycorrhizal symbiosis acts as a major active force of the forest ecosystem processes (Read et al. , 2004). Five types of mycorrhizal association have been described, and among them, two are of major economic and ecological importance: arbuscular mycorrhizas (AM) and ectomycorrhizas (EM) ( Smith & Read, 2008). 1.1.1. Arbuscular mycorrhizas Approximately 70-90% of terrestrial plants are colonized by arbuscular mycorrhizal (AM) fungi (Smith & Read, 2008). AM typically dominate in grasslands, shrublands, and tropical rainforests (Read, 1991).

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  Handbook of Soil Sciences

  Properties and Processes, Second Edition

  • Pan Ming Huang, Yuncong Li, Malcolm E. Sumner, Pan Ming Huang, Yuncong Li, Malcolm E. Sumner(Authors)
  • 2011(Publication Date)
  • CRC Press

    (Publisher)

  From the inner zone of the mantle, some hyphae penetrate between the root cells to form the Hartig net (Figure 24.8d), an intercellular hyphal network inside the root tissues where metabolites are exchanged. The hyphae always remain apoplas-tic and can colonize epidermal and cortical cell layers (Barker et al., 1998). In ECM, plant and fungal cell walls are always in direct contact, forming the interface between the two partners; it has also been observed that the fungus can cause subtle changes in the host cell walls (Balestrini et al., 1996; Martin et al., 2007). 24.4.4 Nutrient Exchanges The success of mycorrhizal fungi in time and space is mainly linked to the nutritional benefits they confer to their plant hosts: They take up phosphate (Pi) and other macronutrients as well as microelements and water from the soil and deliver them to the plant. The fungus, in turn, receives photosynthetic carbo-hydrates. The extraradical mycorrhizal mycelium (ERMM) cap-tures water and nutrients from the soil and is an important sink for host carbon. Inside the roots, carbohydrates and mineral nutrients are then exchanged across the interface between the plant and the fungus (Smith and Smith, 1990). In recent years, several studies have been performed with the aim of investigat-ing the transfer of nutrients between symbionts and, from the Microbiota 24 -33 literature, it seems clear that most of the information available is for AMs and ECM. For this reason, in this section, we will focus on these mycorrhizal categories. 24.4.4.1 Phosphate Improved phosphate uptake is the main benefit for plants in AM symbiosis (Bucher, 2007; Javot et al., 2007). The extensive hyphal network of AM fungi influences the physicochemical properties of the soil and directly or indirectly contributes to the release of phosphate from inorganic complexes of low solu-bility (Parniske, 2008).

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  Mycorrhizal Symbiosis

  • Sally E. Smith, David J. Read(Authors)
  • 1996(Publication Date)
  • Academic Press

    (Publisher)

  Lindeberg and Lindeberg, 1977 ) that ectomycorrhizal fungi, as a group, lack the ability to degrade complex C-containing polymers. The challenge now is to determine the extent of expression of newly revealed enzymic potentials in the ectomycorrhizal root. Recent advances in affinity labelling techniques have produced specific molecular probes for individual components of the plant cell wall. These include monoclonal antibodies against pectic polysaccharides. The use of these in conjunction with more conventional histochemical techniques should enable clarification of the processes whereby compatible associations between plant and fungus lead to the production of a stable interface for nutrient exchange.

  The Mycorrhizal Mantle

  Whereas the Hartig net forms the most extensive interface between fungus and plant, its biomass in most ectomycorrhizas is small relative to that of the overlying mantle. By separating the mantle from the core of selected mycorrhizas of Fagus, Harley and McCready (1952 ; and see Fig. 7.2 c) were able to calculate that 40% of the weight of the colonized root was due to the fungus. This value does not, of course, include the weight of the Hartig net and has been widely, and often loosely, used by later workers even though they were studying other plant-fungus associations growing under different conditions. Vogt et al. (1982 , 1991 ) have reported values similar to those obtained for Fagus from Abies amabilis growing in subalpine forest. However, they observed that in low altitude forest of Pseudotsuga menziesii the sheath constituted only 20% of the root weight. Bearing in mind that Harley and McCready were specifically collecting relatively large ectomycorrhizas, probably those formed by Lactarius subdulcis, with fleshy sheaths, it is reasonable to assume that 40% may be a high value for fungal weight and that values between 20% and 40% would be more commonplace.

  Use of Mantle Structure for Classification of Ectomycorrhizal Types

  The need for a system of classification of mycorrhizal types which enables identification of the fungal associates involved has long been recognized. Apart from the intrinsic interest in the question of diversity of species present on a given plant, a rational system for identification and selection of defined types of the symbiosis is an essential prerequisite for rigorous classification of the functional differences between them. Early attempts to define mycorrhizal types (Melin, 1927 ; Dominik, 1969 ), which were based upon differences of macroscopic and microscopic characteristics, did little to facilitate identification of the fungi involved. Trappe (1967) emphasized the need to identify fungal partners and suggested various hyphal and other microscopic characteristics that could be used. In an analysis of Pseudotsuga mycorrhizas, Zak (1971a , 1973 ) used gross morphological characters and emphasized colour as an important distinguishing feature. Chilvers (1968a)

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  The Rhizosphere

  Biochemistry and Organic Substances at the Soil-Plant Interface, Second Edition

  • Roberto Pinton, Zeno Varanini, Paolo Nannipieri, Roberto Pinton, Zeno Varanini, Paolo Nannipieri(Authors)
  • 2007(Publication Date)
  • CRC Press

    (Publisher)

  Their results suggest that (1) there is a spatial difference in the patterns of fungal gene expression between ECM and EM, (2) urea and polyamine transporters could facilitate the translocation of nitrogen compounds within the EM network, and (3) changes in lipid metabolism may contribute to membrane remodeling during ectomycorrhiza formation. Symbiotic roots provide a niche for mycorrhizal fungi. To bring about a symbiosis, the host plant must trade the fungus demand for carbon for respiration and growth, which is met primarily by glycolytic and anaplerotic processes requiring carbon sources, against its provision of extra nitrogen, phosphate, and minerals [128–130]. Hyphae prospecting the soil absorb nutrients by active Mycorrhizal Fungi: A Fungal Community at the Interface between Soil and Roots 219 metabolism and transport ions and assimilated metabolites to the host root via their strands and rhizomorphs. This mechanism is crucial for the absorption of nutrients that are poorly mobile, such as inorganic phosphate (Pi) and K + , or bound to soil particulates (NH 4 + ). Because ions rapidly absorbed by nonmycorrhizal plant roots become scarce in the rhizosphere, a zone of deficiency forms and the root’s absorption rate mainly depends upon their diffusion rate rather than its own activity. Mycorrhizal hyphae counteract this deficiency, because nutrients translocate through the fungal cells to any sink, such as the root cells, more quickly than they diffuse in the soil [6]. This faster translocation rate is sufficient to explain the enhanced absorption rates of symbiotic roots. In exchange, the fungus receives their carbon compounds. These two-way flows of nutrients and other metabolites take place when physiologically active cells of both partners are in intimate contact [103].

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  Mycorrhizal Symbiosis

  • Sally E. Smith, David J. Read(Authors)
  • 2010(Publication Date)
  • Academic Press

    (Publisher)

  Alexander and Lee, 2005 ).

  A defining feature of tropical rainforest is the enormous diversity of plant species in the communities. In the tree flora alone, Wright (2002) recorded 1175 species in a 0.52 km2 plot of Borneo rainforest. This is more than occur in all of the boreo-temperate forests of the northern hemisphere. Within this diversity it is possible to recognize some patterns with respect to the distribution of mycorrhizal types. While most rainforest tree species associate with AM fungi, there are families of tropical plants which are predominantly or entirely ectomycorrhizal (Alexander, 1989a ). These include the Dipterocarpaceae (

  Lee et al. , 1996

  ), Fagaceae (Comer, 1972 ), many legumes in the Caesalpinoideae (Alexander, 1989b ) and members of the subfamily Leptospermoideae in the Myrtaceae (

  Moyersoen et al. , 2001

  ). Circumstantial evidence suggests that there is a relationship between mycorrhizal type and soil conditions. Whereas trees with AM colonization predominate over large areas of such systems, there are localized occurrences in South American (Singer and Araujo, 1979 , 1986; Henkel, 2003 ), West African (

  Newbery et al. , 1988

  ) and South-East Asian (Whitmore, 1984 ) forests of communities dominated by ECM species. Although these are often restricted to the most nutrient-poor soils with a surface accumulation of litter and raw humus (

  Torti et al. , 2001

  ; Henkel, 2003 ), deductions concerning possible ecological relationships between mycorrhizal and soil types must be drawn with caution in view of the background phylogenetic histories of each family. This complication is best illustrated by the generally ectomycorrhizal Dipterocarpaceae which dominate the rainforests of South-East Asia almost irrespective of soil type (Whitmore, 1984 ), and apparently without particular association with nitrogen-limiting conditions (Alexander and Lee, 2005

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