Mycorrhizas: Anatomy and Cell Biology

182 Pages·2003·22.83 MB·English

by  R. L. Peterson

Mycorrhizas:
Anatomy and Cell Biology
R. Larry Peterson
Department of Botany
University of Guelph
Guelph, ON N1G 2W1
Hugues B. Massicotte
University of Northern British Columbia
Ecosystem Science and Management Program
3333 University Way
Prince George, BC V2N 4Z9
Lewis H. Melville
Department of Botany
University of Guelph
Guelph, ON N1G 2W1
NRC Research Press
Ottawa 2004
©2004 National Research Council of Canada
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National Library of Canada cataloguing in publication data
Peterson, R. Larry
Mycorrhizas : anatomy and cell biology
Includes bibliographical references and an index.
Issued by the National Research Council of Canada.
NRC No. 46325
ISBN 0–660–19087–7 Electronic ISBN 0-660-19372-8
1. Mycorrhizas. 2. Roots (Botany)
I. Massicotte, Hugues B. II. Melville, Lewis H. III. National Research Council Canada. IV. Title.
QK604.2.M92P37 2003 581.4’98 C2003-980254-X
NRC Monograph Publishing Program
Editor:P.B. Cavers (University of Western Ontario)
Editorial Board: H. Alper, OC, FRSC (University of Ottawa); G.L. Baskerville, FRSC (University of British Columbia);
W.G.E. Caldwell, OC, FRSC (University of Western Ontario); S. Gubins (Annual Reviews, Palo Alto, CA); B.K. Hall, FRSC
(Dalhousie University); P. Jefferson (Agriculture and Agri-Food Canada); W.H. Lewis (Washington University, St. Louis,
MO); A.W. May, OC (Memorial University of Newfoundland); G.G.E. Scudder, OC, FRSC (University of British Columbia);
B.P. Dancik, Editor-in-Chief, NRC Research Press (University of Alberta)
Inquiries: Monograph Publishing Program, NRC Research Press, National Research Council of Canada, Ottawa, Ontario
K1A0R6, Canada. Web site: www.monographs.nrc-cnrc.gc.ca
Contents
Preface, vii
Introduction, 1
Root–microorganism interactions are ubiquitous, 1
Mycorrhizal categories, 1
Dark septate fungal endophytes, 2
Microscopy, 2
Organization of book, 2
References, 2
Recent specialized books on mycorrhizas, 3
Box : Mycorrhizas – the most prevalent symbiosis on earth, 4
Chapter 1. Ectomycorrhizas, 5
A. Introduction, 7
1. Definition, 7
2. Plant species involved, 7
3. Fungal species involved, 8
B. Morphology of ectomycorrhizas, 8
C. Mantle, 9
D. Hartig net, 22
E. Extraradical mycelium, 23
F. Specialized ectomycorrhizas – tuberculate mycorrhizas, 38
Box 1: The polyphosphate controversy, 30
Box 2: Are water and nutrients able to pass through the mantle?, 31
Box 3: Root cells may respond to mycorrhizal fungi by developing as transfer cells, 32
Box 4: Can ectomycorrhizal fungi really eat rocks?, 39
Box 5: Growing ectomycorrhizal fungi in the lab, 42
Chapter 2. Ectendomycorrhizas, 43
A. Introduction, 45
1. Definition, 45
2. Plant species involved, 45
3. Fungal species involved, 45
B. Structural characteristics, 45
C. Functions, 54
iii
Chapter 3. Arbuscular mycorrhizas, 55
A. Introduction, 57
1. Definition, 57
2. Plant species involved, 57
3. Fungal species involved, 58
B. Intraradical hyphae, 58
C. Arbuscules, 64
D. Intraradical vesicles, 70
E. Extraradical vesicles, 70
F. Extraradical mycelium, 71
G. Spores, 76
Box 6: Do the lower plants have arbuscular mycorrhizas?, 62
Box 7: Use of ‘hairy roots’in studies with arbuscular mycorrhizal fungi, 63
Box 8: Plant mutants help unravel colonization events in arbuscular mycorrhizas, 65
Box 9: What is the nature of the interface between arbuscular mycorrhizal fungi and root
cells?, 68
Box 10: Arbuscular mycorrhizal fungi harbour intracellular bacteria, 69
Box 11: Dynamic changes in the plant cytoskeleton, 77
Chapter 4. Ericoid mycorrhizas, 81
A. Introduction, 83
1. Definition, 83
2. Plant species involved, 83
3. Fungal species involved, 86
B. Development and structure, 86
C. Extraradical mycelium, 89
D. Functions, 89
Box 12: Liverworts and ericoid species can share common fungal symbionts, 87
Box 13: Investigating the identity of ericoid mycorrhizal fungi, 94
Box 14: Ericoid mycorrhizal fungi access various sources of nitrogen, 95
Chapter 5. Arbutoid mycorrhizas, 97
A. Introduction, 99
1. Definition, 99
2. Plant species involved, 99
3. Fungal species involved, 99
B. Development and structure, 99
C. Functions, 100
iv
Chapter 6. Monotropoid mycorrhizas, 109
A. Introduction, 111
1. Definition, 111
2. Plant species involved, 111
3. Fungal species involved, 111
B. Development and structure, 112
C. Functions, 113
Chapter 7. Orchid mycorrhizas, 123
A. Introduction, 125
1. Definition, 125
2. Plant species involved, 125
3. Fungal species involved, 125
B. Orchid seed germination and protocorm formation, 130
C. Seedling establishment and mature plants, 131
D. Functioning of orchid mycorrhizas, 131
Box 15: Orchids as ‘cheaters’, 143
Box 16: Mycorrhizal fungi alter the cytology of orchid cells, 144
Chapter 8. Dark septate fungal endophytes, 145
A. Introduction, 147
1. Definition, 147
2. Plant species involved, 147
3. Fungal species involved, 147
B. Colonization of roots, 148
C. Functions, 148
References, 155
Glossary, 163
Appendices, 165
Index, 171
v
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Preface
The occurrence of symbiotic relationships mycorrhizas. We hope that the information includ-
between roots and fungi (mycorrhizas) has been ed and the format of the book will stimulate read-
recognized since the early 1800’s and it is now ers to explore mycorrhizas in more detail. Leads
clear that these associations are the most prevalent are given into the literature for further discussion
symbiotic systems on earth. Mycorrhizal associa- of each topic covered.
tions can be found in all ecosystems and in impor- Most of the images presented in the chapters
tant forest and crop species. Based on the structur- are from our own research. Credit is given for
al features of the symbiosis between the plant and those images provided by other researchers and we
the fungus involved, seven categories have been thank them for allowing us to use them. Although
described. Ongoing and more intensive investiga- some references are included in each chapter, no
tions of mycorrhizas in the field and in regions of attempt has been made to provide a comprehen-
the world that have received little attention in the sive literature review for each topic. Several recent
past, will likely result in the present categories reviews and volumes on mycorrhizas provide
being modified and perhaps expanded. excellent detailed discussions of various aspects of
This book has resulted from a long collabora- mycorrhizal associations.
tion among the authors and our shared interest in To provide the most complete descriptions of
exploring the structural diversity of mycorrhizas at mycorrhizas, information has been gained by
various scales. It has become clear from the litera- using a variety of preparative techniques com-
ture and recent international meetings that a bined with a range of microscopical methods. A
majority of the current research on mycorrhizas brief appendix describing the various techniques
involves molecular, physiological and ecological used in preparing the images in the book is includ-
studies. Few structural studies are being pursued ed, primarily as a guide for readers who are new to
in spite of the need for basic information for some the field or have a background that does not
categories of mycorrhizas and the detailed infor- include structural training. Also included is a glos-
mation that can now be obtained as a result of new sary of the most common terms related to structur-
analytical methods. The intention of this book, al aspects of mycorrhizas.
therefore, is to provide, through a series of chap- Financial support has been provided indirectly
ters, a summary of all the mycorrhizal categories by the Natural Sciences and Engineering Research
from a morphological and anatomical perspective. Council of Canada by research grants over many
We strongly believe that the structural information years. We thank all of our former and present
presented will provide researchers in all aspects of undergraduate, graduate, and post-doctoral stu-
mycorrhizal research with a platform from which dents for their excellent contributions, Cameron
to explore questions related to the functioning of Ackerley and Melanie Howarth who, for years,
mycorrhizas. helped us with many aspects of microscopy, Linda
This book will be of interest to undergraduate Tackaberry for editorial assistance, Christopher
and graduate students, secondary school teachers Peterson for helping organize our literature data
and professors who include discussions of mycor- base, and the Universities of Guelph and Northern
rhizas in various subjects that they teach, and British Columbia for providing RLP and HBM
researchers in root biology and various aspects of time to launch this project.
vii
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Introduction
Root–microorganism lished that are devoted to various aspects of myc-
orrhizas. Of the recent books, Smith and Read
interactions are ubiquitous
(1997) is the most complete in terms of coverage
of all categories of mycorrhizal associations; these
Roots of all vascular plants are in intimate con- authors consider structure, physiology and some
tact with a substrate, and whether this is soil, water ecological aspects. Other books are more special-
or tree bark, various abiotic and biotic factors ized in their coverage and are listed at the end of
influence their development and function this section for reference.
(Peterson 1992). A complex array of microorgan-
isms occupies various niches in this substrate and Mycorrhizal categories
this affects roots and, therefore, plant performance
in various ways. For example, many of these Since this volume is concerned with the struc-
organisms are pathogenic fungi or bacteria that are ture of all known mycorrhizal categories, a brief
detrimental to plant growth and reproduction. definition of each is given here. The pioneering
Consequently, considerable effort and expense work of Frank (see Smith and Read 1997) resulted
may be required to control the population density in the recognition of two broad subdivisions of
and (or) pathogenicity of these organisms, particu- mycorrhizas, ectomycorrhizas and endomycor-
larly if they attack crop, horticultural, or forest rhizas. Ectomycorrhizas are characterized by the
species. Other organisms may be beneficial to formation of a mantle and a Hartig net of intercel-
plants and these may be manipulated in ways to lular hyphae on roots of predominantly tree
increase their effect on plant performance. species. Endomycorrhizas are more variable than
Examples include plant growth promoting rhi- ectomycorrhizas in that herbaceous and tree
zobacteria (PGPRs), a group of free-living bacte- species are involved and there is a diversity of fun-
ria that may fix nitrogen, provide growth-promot- gal groups involved in forming these associations.
ing substances to plants, or modify the rhizosphere Endomycorrhizas have, therefore, been further
to make various recalcitrant nutrients available to classified as either arbuscular mycorrhizas, ericoid
plants. Various members of the Rhizobiaceae (e.g., mycorrhizas, arbutoid mycorrhizas, monotropoid
Rhizobium, Bradyrhizobium) and the actino- mycorrhizas, ectendomycorrhizas or orchid myc-
mycete genus Frankia are capable of inducing orrhizas. Each of these categories is characterized
nodules on legumes and several woody species, by the invasion of root cells by fungal hyphae but
respectively, and once housed within nodules, are profound differences occur in the nature of intra-
able to fix atmospheric nitrogen that can be made cellular hypha development.
available to the plant. Arbuscular mycorrhizas (formerly referred to
The most prevalent beneficial organisms asso- as vesicular–arbuscular mycorrhizas) are by far
ciated with plants, however, are soil-inhabiting the most prevalent of all mycorrhizal categories
fungi that form mutualistic root–fungal associa- with more than 80% of all plant species showing
tions referred to as mycorrhizas (Smith and Read an association involving a few fungal genera in
1997). There has been a long history in studying the Glomeromycota. The most diagnostic feature
mycorrhizas (Trappe and Berch 1985; Harley and of this mycorrhiza is the development of intercel-
Smith 1983) and this early work formed a sound lular hyphae, intracellular hyphae and arbuscules
basis for the proliferation of research over the past in root cortical cells (some species also develop
few decades and for the number of books pub- vesicles within and between root cells), and the
1