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Van Bel AJE, van Kesteren WJP, eds. 1999. Plasmodesmata: Structure, function, role in cell communication. 357 pp. Berlin, Heidelberg, New York: Springer. £120.50 (hardback).
414
Book Reviews
and spelling. Thomson's paper is the worst aected, but his paper in the Annals of Botany provides the necessary details. Nevertheless, I recommend purchase of this volume especially to those interested in plant toxins, and to anyone with a general interest in this formidable pteridophyte. Liz Sheeld # 2001 Annals of Botany Company
doi:10.1006/anbo.2000.1330 Van Bel AJE, van Kesteren WJP, eds. 1999. Plasmodesmata: Structure, function, role in cell communication. 357 pp. Berlin, Heidelberg, New York: Springer. £120.50 (hardback). It has been suggested that stomata are the most important ori®ces on the planet. In that case, plasmodesmata probably come a very close second. Their tiny size notwithstanding, the role(s) currently attributed to these botanical nanochannels makes them a cell feature of major importance. Or, to use the common parlance, plasmodesmata are a hot topic, and their in¯uence is nowadays being appreciated in such areas as plant pathology (e.g. virus movement) and biomass production (e.g. pathways of photosynthate transport), and in connection with the big questions of modern biology, such as development and dierentiation (e.g. establishment of symplasmic domains, formation of secondary plasmodesmata, and cell-cell communication). In keeping with this diversity, the range of techniques being used to study plasmodesmata extends from the `old faithful' of transmission electron microscopy to the very latest molecular biological techniques. All these aspects (and many more) of plasmodesmatal biology are covered in the volume edited by van Bel and van Kesteren. After a useful scene-setting review of some of the most puzzling questions concerning plasmodesmata, `Plasmodesmata, a maze of questions' (by van Bel, GuÈnther and van Kesteren), which could easily be sub-titled, `more questions than answers', there follow chapters on: Plasmodesmal imagingÐtowards understanding structure (Botha and Cross); Tissue preparation and substructure of plasmodesmata (Ding); Electrical coupling (van Rijen, Wilders and Jongsma); Use and limitations of ¯uorochromes for plasmodesmal research (Goodwin and Cantrill); Use of GFP-tagged viruses in plasmodesmal research (Oparka, Roberts and Santa Cruz); Evolution of plasmodesmata (Cook and Graham); The perforate septal pore cap of Basidiomycetes (MuÈller, Humbel, van Aelst, van der Krift and Boekhout); Substructure of plasmodesmata (Overall); Multimorphology and nomenclature of plasmodesmata in higher plants (Kollmann and Glockmann); Physiological control of plasmodesmal gating (Schulz); Plasmodesmal coupling and cell dierentiation in algae (Kwiatowska); The symplasmic organization of the shoot apical meristem (van der Schoot and Rinne); The physiological and developmental consequences of plasmodesmal connectivity (Ehlers and van Bel); Plasmodesmata in the phloemloading pathway (Beebe and Russin); P-protein tracking
through plasmodesmata (Thompson); and Plasmodesmata and long-distance virus movement (Derrick and Nelson). Finally, the 17 chapters are matched by an equal number of double-columned pages of index. `Seeing is believing', we are often told. In dealing with plasmodesmata the ability to visualize these tiny features is absolutely crucial to a proper appreciation of their structure and function. Not only are the preparation techniques important, so too are the methods used to interpret the images obtained. The chapters by Botha and Cross, and Ding, are devoted to these issues, and provide the background necessary for a better appreciation of the chapters that follow. Viewed as a whole, the contributions in this volume show how far plasmodesmal studies have come, and are a celebration of the advances that have been made since the early days of electron microscopy. However, they do not shirk the responsibility of a good review in that they point out how far we still have to go to provide the de®nitive view of plasmodesmatal structure, and do not shy away from highlighting de®ciencies in current `knowledge' (even when those alternative views are to be found within other chapters of the book). Possibly in view of the doubts that still surround the ®ne details of plasmodesmatal structure, most of the chapters (and certainly all the `methodological' ones) are careful to stress the limits of the information that dierent techniques can give, and the practical problems inherent in the techniques. That caution is quite refreshing in the brave new world of modern biology where all things seem possible, and enhances the value of the book. The quality of reproduction of the images is good (which is essential in a book where so much relies upon interpretation of micrographs), but some ®gures deserve mention for other reasons. The legend to Fig. 2 on p. 33 refers to `F±L', but `J' is the ®nal panel on this ten-panel plate; presumably `L' should be `I' or `J'? I found Fig. 6 on p. 235 too small, and, as a consequence, confusing. Finally, Fig. 3 on p. 305; although legends are given for the panels A±G, none of the seven panels on the plate appear to be identi®ed with a letter, so matching the legend to the correct panel is not straightforward. One of the most useful features of reviews should be the access to the relevant literature that they provide. However, when I checked an original reference, I noted an error in the volume number cited in the book (Blackman et al., 1998 on p. 20, cited as Plant Journal vol. 10, is in fact volume 15). Having also checked several other references, I think this is an isolated incident, but readers should be aware of this potential problem area. Finally, `typographical errors' appeared to be very few, and all the chapters read well. One of the most satisfying aspects of the book is to see the word symplasm used properly (see Erickson, 1986) in, and consistently between, all the chapters. I'm not sure if this is due to the Editors' in¯uence or the natural erudition of the contributors, but it is most welcome and to be applauded. Currently, there are no competitors for this book, and it is a most worthy `successor' to the landmark volumes on plasmodesmata edited by Gunning and Robards (1976) and Robards et al. (1990). The present collection of chapters
Book Reviews re¯ects the current state of the art of plasmodesmatal research, and their variety should satisfy all those with an interestÐhowever obliqueÐin any aspect of plasmodesmatal biology. It is to be hoped that the ®llip such a collection will give to work on plasmodesmata will soon spawn other volumes in this rapidly expanding and exciting area of plant research. As for the price? I think the less said about it, the better! L I T E R AT U R E C I T E D Erickson RO. 1986. Symplastic growth and symplasmic transport. Plant Physiology 82: 1153. Gunning BES, Robards AW, eds. 1976. Intercellular communication in plants: studies on plasmodesmata. Berlin, Heidelberg, New York: Springer. Robards AW, Lucas WJ, Pitts JD, Jongsma HJ, Spray DC, eds. 1990. Parallels in cell to cell junctions in plants and animals. NATO ASI, series vol H46. Berlin, Heidelberg, New York: Springer.
Nigel Chaey # 2001 Annals of Botany Company
doi:10.1006/anbo.2000.1334 VieÂmont J-D, Crabbe J. 2000. Dormancy in plants. From whole plant behaviour to cellular control. 400 pp. Wallingford: CAB International. £55.00 (hardback). The title is enticing with its promise of explanations for the origins of dormancy in whole plants and the molecular mechanisms for regulation at the cell level. There are 73 authors and 25 chapters. Each chapter expresses thoughts and points of view on dierent aspects of growth arrest, but importantly, all in the absence of cell death. Together, these chapters summarize the outcome of a conference held in Angers in July 1999. Every bud on a plant has a growth cycle to complete before mitotic arrest. Buds do not necessarily cycle synchronously, so each meristem can have an individual time programme. The search is for the signals and changes that cause a cell to cease normal metabolic activity and become essentially quiescent, to hold that quiescent state but remain alive and then to revert back to active metabolic growth. Temperature, light and hydration levels top the list of signals, while changes to membranes, intercellular communication, hormone levels and new gene expressions are seen as interacting controllers. Did dormancy develop from a need to maintain membrane functionality in hostile conditions with the random occurrence of bud dormancy in tropical species giving way to the seasonal photoperiodic and temperature controls we observe in buds and seeds of other latitudes? Certain enzymes associated with membranes, for example, have widely dierent temperature optima which make them sensitive monitors of the environment. Alcohols, as good membrane modi®ers, can enhance the breaking of seed dormancy. We learn of the loss of plasmodesmatal continuity and cytoplasmic isolation of one cell from another within 5 d of apical bud cells of poplars entering dormancy. Nuclear membranes too lose connections with the
415
endoplasmic reticulum. Both events are reversed on the resumption of shoot growth. Calcium normally accumulates in the walls and vacuoles in growing buds, but in short days this changes to the nucleus and cytosol. Before the breaking of dormancy, calcium-ATPase activity shifts from the inner to the outer surface of the plasma membrane. Just how these changes are driven remains unanswered. Are they the cause or the result of dormancy? Water availability and dormancy are also considered at some length. In the tropics, both the shedding of senescent, water-losing leaves and bud rest seem to be imposed by water stress, but as in temperate species, available water does not then necessarily break this dormancy, showing that a truly endodormant condition exists that is subject to other controls such as photoperiod or temperature. There are suggestions that the symplastic import of water and sugars to the xylem is regulated by ATPases so that bud break could be linked to xylem sap acidi®cation. In attempts to track available water in cells of dierent parts of tulip bulbs during storage and renewed growth, nuclear magnetic imaging has shown the progressive redistribution of water to the leaves and ¯oral parts before a renewal of active growth, but again, the question of how the movement of water and the transition from dormancy is actually initiated remains open. Are speci®c dormancy-linked proteins synthesized that determine whether a cell ceases activity? For embryos of seeds that lose almost all their water content this seems certain and the production of dehydrins is well established, but buds do not dehydrate extensively at dormancy and certain dehydrins are still formed. Chilling, rather than dormancy, appears to be the signal for dehydrin production in sibling genotypes of peach. The expression of isoforms of 14.3.3 proteins is lower in dormant barley embryos or when germination is suppressed hormonally. The meaning is elusive, particularly as functions of 14.3.3 proteins are not fully explained to the reader. Hormones, internal or applied, are important in dormancy control, abscisic acid (ABA) being central to dormancy imposition. The genetic regulation of ABA synthesis seems clear. However, internal ABA levels do not necessarily follow directly the dormant or non-dormant condition. ABA does not re-induce dormancy in sprouted tubers! Does ABA achieve dormancy by controlling water potential, ATPase activity or by regulating the cell cycle, and how far are gibberellins and auxin eective in over-riding the constraints of ABA? We are left to ponder these questions. Using apical dominance and lateral bud inhibition in pea plants as a model system for dormancy, decapitation was found to change histone mRNAs in the buds within an hour. Altered levels for other mRNAs were also highly speci®c to certain cells, although a correlation between the growing and the non-growing is not altogether apparent. It is suggested that ABA could repress kinase and cyclin activities in the buds with the requirement then for auxin production to promote and maintain further growth. But is this imposed lateral bud quiescence by a shoot apex comparable to the chilling and photoperiod-induced dormancy in seeds or trees?
Book Reviews
and spelling. Thomson's paper is the worst aected, but his paper in the Annals of Botany provides the necessary details. Nevertheless, I recommend purchase of this volume especially to those interested in plant toxins, and to anyone with a general interest in this formidable pteridophyte. Liz Sheeld # 2001 Annals of Botany Company
doi:10.1006/anbo.2000.1330 Van Bel AJE, van Kesteren WJP, eds. 1999. Plasmodesmata: Structure, function, role in cell communication. 357 pp. Berlin, Heidelberg, New York: Springer. £120.50 (hardback). It has been suggested that stomata are the most important ori®ces on the planet. In that case, plasmodesmata probably come a very close second. Their tiny size notwithstanding, the role(s) currently attributed to these botanical nanochannels makes them a cell feature of major importance. Or, to use the common parlance, plasmodesmata are a hot topic, and their in¯uence is nowadays being appreciated in such areas as plant pathology (e.g. virus movement) and biomass production (e.g. pathways of photosynthate transport), and in connection with the big questions of modern biology, such as development and dierentiation (e.g. establishment of symplasmic domains, formation of secondary plasmodesmata, and cell-cell communication). In keeping with this diversity, the range of techniques being used to study plasmodesmata extends from the `old faithful' of transmission electron microscopy to the very latest molecular biological techniques. All these aspects (and many more) of plasmodesmatal biology are covered in the volume edited by van Bel and van Kesteren. After a useful scene-setting review of some of the most puzzling questions concerning plasmodesmata, `Plasmodesmata, a maze of questions' (by van Bel, GuÈnther and van Kesteren), which could easily be sub-titled, `more questions than answers', there follow chapters on: Plasmodesmal imagingÐtowards understanding structure (Botha and Cross); Tissue preparation and substructure of plasmodesmata (Ding); Electrical coupling (van Rijen, Wilders and Jongsma); Use and limitations of ¯uorochromes for plasmodesmal research (Goodwin and Cantrill); Use of GFP-tagged viruses in plasmodesmal research (Oparka, Roberts and Santa Cruz); Evolution of plasmodesmata (Cook and Graham); The perforate septal pore cap of Basidiomycetes (MuÈller, Humbel, van Aelst, van der Krift and Boekhout); Substructure of plasmodesmata (Overall); Multimorphology and nomenclature of plasmodesmata in higher plants (Kollmann and Glockmann); Physiological control of plasmodesmal gating (Schulz); Plasmodesmal coupling and cell dierentiation in algae (Kwiatowska); The symplasmic organization of the shoot apical meristem (van der Schoot and Rinne); The physiological and developmental consequences of plasmodesmal connectivity (Ehlers and van Bel); Plasmodesmata in the phloemloading pathway (Beebe and Russin); P-protein tracking
through plasmodesmata (Thompson); and Plasmodesmata and long-distance virus movement (Derrick and Nelson). Finally, the 17 chapters are matched by an equal number of double-columned pages of index. `Seeing is believing', we are often told. In dealing with plasmodesmata the ability to visualize these tiny features is absolutely crucial to a proper appreciation of their structure and function. Not only are the preparation techniques important, so too are the methods used to interpret the images obtained. The chapters by Botha and Cross, and Ding, are devoted to these issues, and provide the background necessary for a better appreciation of the chapters that follow. Viewed as a whole, the contributions in this volume show how far plasmodesmal studies have come, and are a celebration of the advances that have been made since the early days of electron microscopy. However, they do not shirk the responsibility of a good review in that they point out how far we still have to go to provide the de®nitive view of plasmodesmatal structure, and do not shy away from highlighting de®ciencies in current `knowledge' (even when those alternative views are to be found within other chapters of the book). Possibly in view of the doubts that still surround the ®ne details of plasmodesmatal structure, most of the chapters (and certainly all the `methodological' ones) are careful to stress the limits of the information that dierent techniques can give, and the practical problems inherent in the techniques. That caution is quite refreshing in the brave new world of modern biology where all things seem possible, and enhances the value of the book. The quality of reproduction of the images is good (which is essential in a book where so much relies upon interpretation of micrographs), but some ®gures deserve mention for other reasons. The legend to Fig. 2 on p. 33 refers to `F±L', but `J' is the ®nal panel on this ten-panel plate; presumably `L' should be `I' or `J'? I found Fig. 6 on p. 235 too small, and, as a consequence, confusing. Finally, Fig. 3 on p. 305; although legends are given for the panels A±G, none of the seven panels on the plate appear to be identi®ed with a letter, so matching the legend to the correct panel is not straightforward. One of the most useful features of reviews should be the access to the relevant literature that they provide. However, when I checked an original reference, I noted an error in the volume number cited in the book (Blackman et al., 1998 on p. 20, cited as Plant Journal vol. 10, is in fact volume 15). Having also checked several other references, I think this is an isolated incident, but readers should be aware of this potential problem area. Finally, `typographical errors' appeared to be very few, and all the chapters read well. One of the most satisfying aspects of the book is to see the word symplasm used properly (see Erickson, 1986) in, and consistently between, all the chapters. I'm not sure if this is due to the Editors' in¯uence or the natural erudition of the contributors, but it is most welcome and to be applauded. Currently, there are no competitors for this book, and it is a most worthy `successor' to the landmark volumes on plasmodesmata edited by Gunning and Robards (1976) and Robards et al. (1990). The present collection of chapters
Book Reviews re¯ects the current state of the art of plasmodesmatal research, and their variety should satisfy all those with an interestÐhowever obliqueÐin any aspect of plasmodesmatal biology. It is to be hoped that the ®llip such a collection will give to work on plasmodesmata will soon spawn other volumes in this rapidly expanding and exciting area of plant research. As for the price? I think the less said about it, the better! L I T E R AT U R E C I T E D Erickson RO. 1986. Symplastic growth and symplasmic transport. Plant Physiology 82: 1153. Gunning BES, Robards AW, eds. 1976. Intercellular communication in plants: studies on plasmodesmata. Berlin, Heidelberg, New York: Springer. Robards AW, Lucas WJ, Pitts JD, Jongsma HJ, Spray DC, eds. 1990. Parallels in cell to cell junctions in plants and animals. NATO ASI, series vol H46. Berlin, Heidelberg, New York: Springer.
Nigel Chaey # 2001 Annals of Botany Company
doi:10.1006/anbo.2000.1334 VieÂmont J-D, Crabbe J. 2000. Dormancy in plants. From whole plant behaviour to cellular control. 400 pp. Wallingford: CAB International. £55.00 (hardback). The title is enticing with its promise of explanations for the origins of dormancy in whole plants and the molecular mechanisms for regulation at the cell level. There are 73 authors and 25 chapters. Each chapter expresses thoughts and points of view on dierent aspects of growth arrest, but importantly, all in the absence of cell death. Together, these chapters summarize the outcome of a conference held in Angers in July 1999. Every bud on a plant has a growth cycle to complete before mitotic arrest. Buds do not necessarily cycle synchronously, so each meristem can have an individual time programme. The search is for the signals and changes that cause a cell to cease normal metabolic activity and become essentially quiescent, to hold that quiescent state but remain alive and then to revert back to active metabolic growth. Temperature, light and hydration levels top the list of signals, while changes to membranes, intercellular communication, hormone levels and new gene expressions are seen as interacting controllers. Did dormancy develop from a need to maintain membrane functionality in hostile conditions with the random occurrence of bud dormancy in tropical species giving way to the seasonal photoperiodic and temperature controls we observe in buds and seeds of other latitudes? Certain enzymes associated with membranes, for example, have widely dierent temperature optima which make them sensitive monitors of the environment. Alcohols, as good membrane modi®ers, can enhance the breaking of seed dormancy. We learn of the loss of plasmodesmatal continuity and cytoplasmic isolation of one cell from another within 5 d of apical bud cells of poplars entering dormancy. Nuclear membranes too lose connections with the
415
endoplasmic reticulum. Both events are reversed on the resumption of shoot growth. Calcium normally accumulates in the walls and vacuoles in growing buds, but in short days this changes to the nucleus and cytosol. Before the breaking of dormancy, calcium-ATPase activity shifts from the inner to the outer surface of the plasma membrane. Just how these changes are driven remains unanswered. Are they the cause or the result of dormancy? Water availability and dormancy are also considered at some length. In the tropics, both the shedding of senescent, water-losing leaves and bud rest seem to be imposed by water stress, but as in temperate species, available water does not then necessarily break this dormancy, showing that a truly endodormant condition exists that is subject to other controls such as photoperiod or temperature. There are suggestions that the symplastic import of water and sugars to the xylem is regulated by ATPases so that bud break could be linked to xylem sap acidi®cation. In attempts to track available water in cells of dierent parts of tulip bulbs during storage and renewed growth, nuclear magnetic imaging has shown the progressive redistribution of water to the leaves and ¯oral parts before a renewal of active growth, but again, the question of how the movement of water and the transition from dormancy is actually initiated remains open. Are speci®c dormancy-linked proteins synthesized that determine whether a cell ceases activity? For embryos of seeds that lose almost all their water content this seems certain and the production of dehydrins is well established, but buds do not dehydrate extensively at dormancy and certain dehydrins are still formed. Chilling, rather than dormancy, appears to be the signal for dehydrin production in sibling genotypes of peach. The expression of isoforms of 14.3.3 proteins is lower in dormant barley embryos or when germination is suppressed hormonally. The meaning is elusive, particularly as functions of 14.3.3 proteins are not fully explained to the reader. Hormones, internal or applied, are important in dormancy control, abscisic acid (ABA) being central to dormancy imposition. The genetic regulation of ABA synthesis seems clear. However, internal ABA levels do not necessarily follow directly the dormant or non-dormant condition. ABA does not re-induce dormancy in sprouted tubers! Does ABA achieve dormancy by controlling water potential, ATPase activity or by regulating the cell cycle, and how far are gibberellins and auxin eective in over-riding the constraints of ABA? We are left to ponder these questions. Using apical dominance and lateral bud inhibition in pea plants as a model system for dormancy, decapitation was found to change histone mRNAs in the buds within an hour. Altered levels for other mRNAs were also highly speci®c to certain cells, although a correlation between the growing and the non-growing is not altogether apparent. It is suggested that ABA could repress kinase and cyclin activities in the buds with the requirement then for auxin production to promote and maintain further growth. But is this imposed lateral bud quiescence by a shoot apex comparable to the chilling and photoperiod-induced dormancy in seeds or trees?