Arbuscular Mycorrhizas : Physiology and Function

Recent years have brought an upsurge of interest in the study of arbuscular mycorrhizal (AM) fungi, partly due to the realization that the effective utilization of these symbiotic soil fungi is likely to be essential in sustainable agriculture. Impressive progress has been made during the last decade in the study of this symbiosis largely as a result of increasing exploitation of molecular tools. Although early emphasis was placed on the use of molecular tools to study physiological processes triggered by the symbiosis, such as expression of symbiosis-specific polypeptides and modulation of host defences, other applications await. It was obvious to us that gathering leaders in the field to summarize these topics and point out research needs was necessary if we were to understand the physiology and function of AM fungi at a molecular level. In addition, we have taken the opportunity to present these reviews in a logical sequence of topics ranging from the initiation of the life cycle of the fungus to its functions in plant growth and in the below ground ecosystem. It was a challenge to limit this flood of information to the confines of one text. This is a very exciting time for mycorrhiza biologists and it is our hope that some of this excitement is conveyed to our readers. Front Matter....Pages i-1 Mycorrhizal Fungi Influence Soil Structure....Pages 3-18 Mycorrhizal Symbiosis and Plant Reproduction....Pages 19-46 Spore Germination and Pre-Symbiotic Mycelial Growth....Pages 47-68 Modification of Plant Gene Expression....Pages 69-84 Symbiotic Exchange of Nutrients in Arbuscular Mycorrhizas: Transport and Transfer of Phosphorus....Pages 85-106 Carbon Partitioning, Cost, and Metabolism of Arbuscular Mycorrhizas....Pages 107-129 Effects of Genetic Differences among Crop Species and Cultivars Upon the Arbuscular Mycorrhizal Symbiosis....Pages 131-146 The Use of Plant Mutants to Study Regulation of Colonization by AM Fungi....Pages 147-171 Modulation of Host Defence Systems....Pages 173-200 Stomatal Behavior of Arbuscular Mycorrhizal Plants....Pages 201-237 Interactions of arbuscular mycorrhizal fungi with other soil organisms....Pages 239-262 Hormonal Balance in Plants During Colonization by Mycorrhizal Fungi....Pages 263-285 In Vitro and in Situ Techniques to Examine the Role of Roots and Root Exudates During AM Fungus-Host Interactions....Pages 287-305 Nutrient uptake....Pages 307-343 Effects of Mycorrhizas on Plant Tolerance to Diseases....Pages 345-365 Back Matter....Pages 367-372

This book provides a structured compilation of reviews of what is known about arbuscular mycorrhizal symbiosis. Topics were selected to cover major steps in the life cycle of AM fungi (germination, signaling/recognition prior to colonization, and host regulation of colonization). Aspects of the physiological interaction within the root for which there has been exciting recent progress (regulation of host defenses, bidirectional transport of nutrients, modification of gene expression, and carbon metabolism) are then discussed. The focus then widens to effects of the mycorrhiza upon the whole plant (nutrition, water relations, reproduction, and resistance to disease), and expands further to essential aspects of the role of AM fungi in soil ecology (soil aggregation, and interactions with other soil microbes).
Leaders in the field present critical reviews and point toward areas for future research. Therefore, this volume should be helpful for both researchers in the field and those interested in a thorough knowledge of this important symbiosis.