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Water transport in plants under climatic stress
Agriculture
Ecosystems & Enwronment ELSEVIER
Agriculture, Ecosystems and Environment 49 (1994) 217-219
Book Reviews
Water transportin plants Water Transport in Plants under Climatic Stress, M.Borghetti, J. Grace and A. Raschi (Editors), Cambridge University Press, £35.00/ $59.95, hardback, ISBN0 521 44219 2. Cavitations are fun. One can almost hear the sounds of merriment and of champagne corks popping in John Milburn's laboratory as he describes, in his entertaining chapter in this book, the first detection of the sounds made by a parched plant, 30 years ago. But despite their entertainment value, I have long suspected that cavitations are unimportant in influencing the daily life of a plant in a real environment. My prejudice comes from having watched thousands of wheat plants grow in the field from sowing to maturity during a terminal drought, with their root systems constrained to allow only one seminal root axis and its attendant laterals to explore the soil. Each axis of a wheat plant contains only one substantial metaxylem vessel through which all of the water entering the shoot must eventually pass, so any cavitation in this vessel would result in the rapid death of a plant, a visual rather than acoustic detection of cavitation. Very few of these plants died before maturity, despite their arid environment. Hence, I thought, protection against cavitation must be a problem that evolution could easily solve wherever it mattered. Certainly cavitations might occur in less crucial vascular tissue than the metaxylem vessels in wheat roots, but most plants have abundant carrying capacity in their xylem, and the loss of even a large proportion of it would have little effect on the water status of the plant, I thought. This book is the outcome of a meeting in Italy Elsevier Science B.V. SSDI 0167-8809 ( 94 )00490-6
in 1990 that addressed the hydraulic behaviour of the xylem, and especially cavitations and their consequences. In addition to Milburn's, the book contains several other fairly general articles of high standard. These include a scholarly discussion of the physics of cavitation by Oertli, a revisitation by Jones and Suthedand of their speculation that the productivity of a plant might increase when the stomata remained open despite an increased risk of cavitation, an elegant account by Grace of the still puzzling phenomenon of how embolised vessels may be refilled, and, preceding them all, a prologue by Jarvis that examines the possible implications of global atmospheric change for plant water relations. In addition there are two excellent articles on cavitation in cold-stressed trees. One, by Robson and Petty, offers an original explanation of how tracheids in conifers survive freezing and thawing without losing their ability to carry water. The other, by Sperry, examines the water relations of four co-occurring species that contrast markedly in the ways they cavitate and repair the carrying capacity of their xylem, and thoughtfully discusses the ecological significance of their contrasting behaviour. The remaining three quarters of the book mostly concerns descriptive case studies of water relations of plants, plus some articles on techniques. If you are a practitioner in the burgeoning cavitation industry, then the articles I have mentioned are necessary reading. If you teach advanced plant physiology, then you will find excellent material with which to challenge your students in many of these articles. If you are a sceptical observer of the cavitation industry then this book is unlikely to dent your scepticism. Almost no evidence is presented that suggests that cavitation affects the welfare of plants in their
218
Book Reviews /Agriculture, Ecosystems and Environment 49 (1994) 217-219
normal environments. A pervading belief comes through that cavitation is important, but that plants behave so as to minimise the damage so that you just can't quite see it in their overall performance. This belief is slightly reminiscent of the story of the drunk who (successfully) keeps the pink elephants at bay by continually pulling his left ear lobe. Only Sperry's article seriously addresses the ecological significance of cavitation, and although he finds intriguing correlations that suggest that cavitation may limit the environmental range of at least one species, he remains cautious about his ecological conclusions. JOHN PASSIOURA
CSIRO Division of Plant Industry Canberra Australia
Biological diversity Biodiversity and Ecosystem Function, E.D. Schulze and H.A. Mooney (Editors), Ecological Studies (Analysis and Synthesis) 99, Springer, Berlin, 1993, xxvii + 525 pp.,DM278.00, Hardback, ISBN 3-540-558047. The book comprises most of the contributions delivered at a Symposium held near Bayreuth (Germany) in October 1991. It was organized by the Scientific Steering Committee of Ecosystem Function of Diversity which is part of a larger, joint IUBS, SCOPE, and MAB (UNESCO) global program. The crucial question authors from widely different disciplines were asked to confront themselves with was to what extent alterations in the composition of ecosystems impact on the way the latter operate and/or provide services. In his introduction, P.R. Ehrlich formulates this question in a somewhat more practical and abrupt manner in saying "biodiversity and ecosystem
function need we know more ?". His answer is unequivocally 'yes' as far as science is concerned, and 'no' in terms of taking action now. A total of 38 scientists from nine countries have attempted to summarize the present knowledge in 23 chapters covering the same number of specialized areas of research. These were divided into six sections. Ecosystem function (Section A), includes three papers describing the basic relationships between biological diversity and biogeochemistry in terrestrial ecosystem generally, in agricultural systems more specifically, or with the nutrient cycles within pelagic systems. Sections B and C under the headings Functional groups and Species interactions, follow a very similar pattern of approach. Section B deals with the free-living soil microorganisms as a whole that contribute to the various biogeochemical cycles, with the plant traits in general and the adaptive strategies which influence their role in ecosystem functions, and with the scaling from individual species to vegetation. Section C is concerned with the evolution of the main groups of basidiomycetan fungi, with the role of parasites and pathogens in the dynamics of plant populations, and with the various aspects of plant-microbe mutualisms. It also includes the only chapter in the volume that considers animal diversity, i.e. the very peculiar food web of dipteran insects inducing galls in thistle species. In view of the tremendous impact microorganisms have on the present systems, which is recognized by many contributors, it is surprising to observe that our knowledge of the most important fungal groups (e.g. the rust fungi) is still very much at the level of what G~iumann (1964), for example, had accumulated almost half a century ago! Sections D (Community interactions) and E (Ecosystem integrity) tackle basic problems of biodiversity. Under the first topic, the identification of keystone species within each system is discussed, and the questions of common and rare plants is addressed, of how many of them are truly required, or redundant in ecosystems, and concludes with an overview of the successions in ecological communities. The fifth Section focuses on the various concepts of persistence, stability, resilience, and resistance to changes in
Ecosystems & Enwronment ELSEVIER
Agriculture, Ecosystems and Environment 49 (1994) 217-219
Book Reviews
Water transportin plants Water Transport in Plants under Climatic Stress, M.Borghetti, J. Grace and A. Raschi (Editors), Cambridge University Press, £35.00/ $59.95, hardback, ISBN0 521 44219 2. Cavitations are fun. One can almost hear the sounds of merriment and of champagne corks popping in John Milburn's laboratory as he describes, in his entertaining chapter in this book, the first detection of the sounds made by a parched plant, 30 years ago. But despite their entertainment value, I have long suspected that cavitations are unimportant in influencing the daily life of a plant in a real environment. My prejudice comes from having watched thousands of wheat plants grow in the field from sowing to maturity during a terminal drought, with their root systems constrained to allow only one seminal root axis and its attendant laterals to explore the soil. Each axis of a wheat plant contains only one substantial metaxylem vessel through which all of the water entering the shoot must eventually pass, so any cavitation in this vessel would result in the rapid death of a plant, a visual rather than acoustic detection of cavitation. Very few of these plants died before maturity, despite their arid environment. Hence, I thought, protection against cavitation must be a problem that evolution could easily solve wherever it mattered. Certainly cavitations might occur in less crucial vascular tissue than the metaxylem vessels in wheat roots, but most plants have abundant carrying capacity in their xylem, and the loss of even a large proportion of it would have little effect on the water status of the plant, I thought. This book is the outcome of a meeting in Italy Elsevier Science B.V. SSDI 0167-8809 ( 94 )00490-6
in 1990 that addressed the hydraulic behaviour of the xylem, and especially cavitations and their consequences. In addition to Milburn's, the book contains several other fairly general articles of high standard. These include a scholarly discussion of the physics of cavitation by Oertli, a revisitation by Jones and Suthedand of their speculation that the productivity of a plant might increase when the stomata remained open despite an increased risk of cavitation, an elegant account by Grace of the still puzzling phenomenon of how embolised vessels may be refilled, and, preceding them all, a prologue by Jarvis that examines the possible implications of global atmospheric change for plant water relations. In addition there are two excellent articles on cavitation in cold-stressed trees. One, by Robson and Petty, offers an original explanation of how tracheids in conifers survive freezing and thawing without losing their ability to carry water. The other, by Sperry, examines the water relations of four co-occurring species that contrast markedly in the ways they cavitate and repair the carrying capacity of their xylem, and thoughtfully discusses the ecological significance of their contrasting behaviour. The remaining three quarters of the book mostly concerns descriptive case studies of water relations of plants, plus some articles on techniques. If you are a practitioner in the burgeoning cavitation industry, then the articles I have mentioned are necessary reading. If you teach advanced plant physiology, then you will find excellent material with which to challenge your students in many of these articles. If you are a sceptical observer of the cavitation industry then this book is unlikely to dent your scepticism. Almost no evidence is presented that suggests that cavitation affects the welfare of plants in their
218
Book Reviews /Agriculture, Ecosystems and Environment 49 (1994) 217-219
normal environments. A pervading belief comes through that cavitation is important, but that plants behave so as to minimise the damage so that you just can't quite see it in their overall performance. This belief is slightly reminiscent of the story of the drunk who (successfully) keeps the pink elephants at bay by continually pulling his left ear lobe. Only Sperry's article seriously addresses the ecological significance of cavitation, and although he finds intriguing correlations that suggest that cavitation may limit the environmental range of at least one species, he remains cautious about his ecological conclusions. JOHN PASSIOURA
CSIRO Division of Plant Industry Canberra Australia
Biological diversity Biodiversity and Ecosystem Function, E.D. Schulze and H.A. Mooney (Editors), Ecological Studies (Analysis and Synthesis) 99, Springer, Berlin, 1993, xxvii + 525 pp.,DM278.00, Hardback, ISBN 3-540-558047. The book comprises most of the contributions delivered at a Symposium held near Bayreuth (Germany) in October 1991. It was organized by the Scientific Steering Committee of Ecosystem Function of Diversity which is part of a larger, joint IUBS, SCOPE, and MAB (UNESCO) global program. The crucial question authors from widely different disciplines were asked to confront themselves with was to what extent alterations in the composition of ecosystems impact on the way the latter operate and/or provide services. In his introduction, P.R. Ehrlich formulates this question in a somewhat more practical and abrupt manner in saying "biodiversity and ecosystem
function need we know more ?". His answer is unequivocally 'yes' as far as science is concerned, and 'no' in terms of taking action now. A total of 38 scientists from nine countries have attempted to summarize the present knowledge in 23 chapters covering the same number of specialized areas of research. These were divided into six sections. Ecosystem function (Section A), includes three papers describing the basic relationships between biological diversity and biogeochemistry in terrestrial ecosystem generally, in agricultural systems more specifically, or with the nutrient cycles within pelagic systems. Sections B and C under the headings Functional groups and Species interactions, follow a very similar pattern of approach. Section B deals with the free-living soil microorganisms as a whole that contribute to the various biogeochemical cycles, with the plant traits in general and the adaptive strategies which influence their role in ecosystem functions, and with the scaling from individual species to vegetation. Section C is concerned with the evolution of the main groups of basidiomycetan fungi, with the role of parasites and pathogens in the dynamics of plant populations, and with the various aspects of plant-microbe mutualisms. It also includes the only chapter in the volume that considers animal diversity, i.e. the very peculiar food web of dipteran insects inducing galls in thistle species. In view of the tremendous impact microorganisms have on the present systems, which is recognized by many contributors, it is surprising to observe that our knowledge of the most important fungal groups (e.g. the rust fungi) is still very much at the level of what G~iumann (1964), for example, had accumulated almost half a century ago! Sections D (Community interactions) and E (Ecosystem integrity) tackle basic problems of biodiversity. Under the first topic, the identification of keystone species within each system is discussed, and the questions of common and rare plants is addressed, of how many of them are truly required, or redundant in ecosystems, and concludes with an overview of the successions in ecological communities. The fifth Section focuses on the various concepts of persistence, stability, resilience, and resistance to changes in