Directory UMM :Data Elmu:jurnal:T:Tree Physiology:vol17.1997:
603
Plant Stems: Physiology and Functional Morphology
BARBARA L. GARTNER, Editor
Academic Press, 525 B Street, Suite 1900, San Diego, CA 92101-4495; 1995,440 pages, hardcover, $89.95 US, ISBN 0-12-276460-9
Tree stems are black boxes. When mature, they can be very
difficult to study in situ. They may be very tall (100 meters)
and have large diameters (several meters). Their internal structure is complex, ranging from fairly homogeneous wood comprised largely of dead xylem elements in the conifers, to
anastomosing primary vascular bundles embedded in a matrix
of parenchyma in the monocotyledons, to heterogeneous wood
with a variety of living and dead xylem elements in the dicotyledons. A stem changes structure and function with distance
from its center (e.g., in woody stems: heartwood, sapwood,
lateral meristems, phloem, and outer bark). The outer bark is
viewed primarily as a protective sheath for the stem; it also acts
as an efficient cloaking device to prevent easy access by
researchers to the internal functions of the stem. All stem
functions must integrate to support the rest of the tree. Stems
are tied to leaves at stem tops and roots at stem bases. Water
and nutrients in the stem destined for leaves enter through
roots; photosynthate destined for roots is produced in the
leaves. So, it is difficult to investigate excised stems and infer
normal function from the results. Most tree stems are not
disposable (as are most leaves and fine roots and the stems of
many shrubs); destructive research on tree stems usually
means sacrificing the entire tree. Nonetheless, understanding
stem biology is critical to better ecological modeling, agriculture, wildlife management, lumber production, and other natural resource management. As understanding and techniques
and technology improve, the limitations that have faced the
biologists and engineers are gradually being overcome.
The improvements in stem research are clearly seen in
ecology. Ecology is a synthetic field that is based upon the
integration of various other fields to understand how organisms relate to their environments. Historically, ecosystem
modelers treated whole trees as black boxes, with the uptake
and release of energy, water, nutrients, and carbon described
with little consideration for the internal processes that influenced fluxes. At the same time, plant physiologists emphasized
processes affecting photosynthesis, because the conversion of
light and carbon to food is basic to life on earth. Physiologists
also studied respiration and water relations which are integral
to determining net carbon gain. The easily accessible leaves
and somewhat less accessible fine roots were the site of most
research. New knowledge from this research was incorporated
into the ecological models, but then the tree stems, rather than
the whole tree, were treated as black boxes. As understanding
of the physiological ecology of trees improved over the last ten
years and ecologists became aware of the critical role of tree
stems, ecologists have begun to collaborate with taxonomists,
morphologists, anatomists, physiologists, and engineers to investigate tree stems in their own right and to incorporate the
new data into ecosystem models (e.g., the dynamics of stem
water storage). Interactions with pathologists and zoologists,
including entomologists, are elaborating and expanding the
concepts of stem functions to include interactions with and
internal responses to other taxa.
Plant Stems: Physiology and Functional Morphology is a
collection of comprehensive review papers by leading researchers on what is known and what is not known about
stems, with an emphasis on tree stems. The product of a
workshop held recently in Oregon, it is also a call for the
integration of research on stems from different fields. It is the
first attempt to synthesize knowledge from diverse fields into
a coherent concept of an integrated stem. Gartner, the editor,
carefully organized the material into five sections: stem architecture in plant performance, stems in the transport and storage
of water, live stem cells in plant performance, stems in preventing or reacting to plant injury, and synthesis. The topics covered in various chapters include an impressive array of
research areas: structural support; short- and long-distance
transport; water, nutrient, and metabolite storage; stem photosynthesis; epiflora and epifauna; development; and defense
against and reaction to disturbances such as fire, pollution, and
pathogens. Authors frequently cross-reference other chapters.
From necessity, some of the discussions are speculative and
many examples are from herbaceous plants. Although much of
the reported research is from the North American and European temperate zones, African and Asian species and tropical
and boreal species are mentioned (e.g., palms and tree ferns).
In this context, ‘‘trees’’ are woody plants (including shrubs) or
other arborescent vascular plants. Frequently, investigating
organisms that operate at environmental extremes or that occupy morphologically, anatomically, or functionally fringe positions, gives insight into ‘‘typical’’ organisms. The authors cite
such examples often, clearly indicating the features that distinguish the example from typical plants. As a result, readers
develop an appreciation for the breadth of solutions to functional problems. The approach challenges readers to think
about the tradeoffs inherent in various solutions. Readers may
disagree with some of the assertions, but ‘‘Plant Stems’’ will
have challenged them to view stems in a more integrated way.
The editor and authors have produced a good and timely
synthesis on the function of tree stems. Most of my criticisms
are minor. It is not possible to cover all aspects of stem
physiology in such a volume. I especially missed more discussion on stem gas exchange and internal aeration. There is a
chapter on stems and air pollution, although the book does not
discuss the effects of groundwater pollution on stems. But
given the wide structural and functional variation in stems, it
is remarkable that this book has so comprehensively covered
their functions and interactions.
Some chapters are very clear and easy to follow, others leave
the reader to fill in gaps. Not all of the authors are clear about
when they speculate. Terminology from several research fields
is used in the text, but many terms are not defined. Defining
more of the terminology would ease reading across disciplines.
TREE PHYSIOLOGY ON-LINE at http://www.heronpublishing.com
604
The chapters by Gartner, Givinish, Holbrook, Nilsen, Pate and
Jeschke, and Weber and Grulke are especially well written and
clear. Some authors clearly state where the most important
areas for future research are, and some emphasize the importance of more research in terms of real-world applications.
As I read the review chapters, I looked forward to a summary
chapter that pulled all of stem biology together, but an entire
second volume would be required to develop a synthesis of the
preceding chapters with one voice. Hinckley and Schulte’s
summary chapter reiterates some of the important concepts
developed in the book, such as redundancy and modularity of
construction, the incorporation of life history into the annual
rings and structure of stems of individual trees, the energy
costs of building disposable and nondisposable stems, responding to environmental signals and communication among
plant organs, difficulties in research on tree stems, interactions
among stem functions and processes, and trade-offs among
and optimization of functional strategies.
The book’s index limits its usefulness for reference. Not all
occurrences of some terms used within the text are listed (e.g.,
integrated physiological unit), and I couldn’t find index entries
for monocotyledons, palms, primary xylem, or vascular bun-
dles----all of which are discussed in various places throughout
the volume. Also, inclusion of taxa in the index, or in a separate
index, would have been very useful.
This book deserves a wide readership. Researchers, graduate students, and advanced undergraduates in any field concerned with plant growth or function will find the book
informative and thought provoking. College teachers and laboratory instructors will be able to glean ideas for student projects from the many suggestions for proposed research.
Referring to the ‘‘wide diversity of perspectives’’ in this volume, Hinckley and Schulte write, ‘‘...we tend to study our small
piece of the stem, but if we are to understand it as an entire
structure we must take this broader view.’’ The next steps are
for botanists, ecologists, and other scientists to read this book,
do the research, and integrate the results among their fields.
Clearly, the black box is being uncloaked----the time for integration and synthesis has arrived!
Ann M. Lewis, Department of Forestry and Wildlife Management, Holdsworth Hall, University of Massachusetts, Amherst,
MA 01003-4210, USA.
TREE PHYSIOLOGY VOLUME 17, 1997
Plant Stems: Physiology and Functional Morphology
BARBARA L. GARTNER, Editor
Academic Press, 525 B Street, Suite 1900, San Diego, CA 92101-4495; 1995,440 pages, hardcover, $89.95 US, ISBN 0-12-276460-9
Tree stems are black boxes. When mature, they can be very
difficult to study in situ. They may be very tall (100 meters)
and have large diameters (several meters). Their internal structure is complex, ranging from fairly homogeneous wood comprised largely of dead xylem elements in the conifers, to
anastomosing primary vascular bundles embedded in a matrix
of parenchyma in the monocotyledons, to heterogeneous wood
with a variety of living and dead xylem elements in the dicotyledons. A stem changes structure and function with distance
from its center (e.g., in woody stems: heartwood, sapwood,
lateral meristems, phloem, and outer bark). The outer bark is
viewed primarily as a protective sheath for the stem; it also acts
as an efficient cloaking device to prevent easy access by
researchers to the internal functions of the stem. All stem
functions must integrate to support the rest of the tree. Stems
are tied to leaves at stem tops and roots at stem bases. Water
and nutrients in the stem destined for leaves enter through
roots; photosynthate destined for roots is produced in the
leaves. So, it is difficult to investigate excised stems and infer
normal function from the results. Most tree stems are not
disposable (as are most leaves and fine roots and the stems of
many shrubs); destructive research on tree stems usually
means sacrificing the entire tree. Nonetheless, understanding
stem biology is critical to better ecological modeling, agriculture, wildlife management, lumber production, and other natural resource management. As understanding and techniques
and technology improve, the limitations that have faced the
biologists and engineers are gradually being overcome.
The improvements in stem research are clearly seen in
ecology. Ecology is a synthetic field that is based upon the
integration of various other fields to understand how organisms relate to their environments. Historically, ecosystem
modelers treated whole trees as black boxes, with the uptake
and release of energy, water, nutrients, and carbon described
with little consideration for the internal processes that influenced fluxes. At the same time, plant physiologists emphasized
processes affecting photosynthesis, because the conversion of
light and carbon to food is basic to life on earth. Physiologists
also studied respiration and water relations which are integral
to determining net carbon gain. The easily accessible leaves
and somewhat less accessible fine roots were the site of most
research. New knowledge from this research was incorporated
into the ecological models, but then the tree stems, rather than
the whole tree, were treated as black boxes. As understanding
of the physiological ecology of trees improved over the last ten
years and ecologists became aware of the critical role of tree
stems, ecologists have begun to collaborate with taxonomists,
morphologists, anatomists, physiologists, and engineers to investigate tree stems in their own right and to incorporate the
new data into ecosystem models (e.g., the dynamics of stem
water storage). Interactions with pathologists and zoologists,
including entomologists, are elaborating and expanding the
concepts of stem functions to include interactions with and
internal responses to other taxa.
Plant Stems: Physiology and Functional Morphology is a
collection of comprehensive review papers by leading researchers on what is known and what is not known about
stems, with an emphasis on tree stems. The product of a
workshop held recently in Oregon, it is also a call for the
integration of research on stems from different fields. It is the
first attempt to synthesize knowledge from diverse fields into
a coherent concept of an integrated stem. Gartner, the editor,
carefully organized the material into five sections: stem architecture in plant performance, stems in the transport and storage
of water, live stem cells in plant performance, stems in preventing or reacting to plant injury, and synthesis. The topics covered in various chapters include an impressive array of
research areas: structural support; short- and long-distance
transport; water, nutrient, and metabolite storage; stem photosynthesis; epiflora and epifauna; development; and defense
against and reaction to disturbances such as fire, pollution, and
pathogens. Authors frequently cross-reference other chapters.
From necessity, some of the discussions are speculative and
many examples are from herbaceous plants. Although much of
the reported research is from the North American and European temperate zones, African and Asian species and tropical
and boreal species are mentioned (e.g., palms and tree ferns).
In this context, ‘‘trees’’ are woody plants (including shrubs) or
other arborescent vascular plants. Frequently, investigating
organisms that operate at environmental extremes or that occupy morphologically, anatomically, or functionally fringe positions, gives insight into ‘‘typical’’ organisms. The authors cite
such examples often, clearly indicating the features that distinguish the example from typical plants. As a result, readers
develop an appreciation for the breadth of solutions to functional problems. The approach challenges readers to think
about the tradeoffs inherent in various solutions. Readers may
disagree with some of the assertions, but ‘‘Plant Stems’’ will
have challenged them to view stems in a more integrated way.
The editor and authors have produced a good and timely
synthesis on the function of tree stems. Most of my criticisms
are minor. It is not possible to cover all aspects of stem
physiology in such a volume. I especially missed more discussion on stem gas exchange and internal aeration. There is a
chapter on stems and air pollution, although the book does not
discuss the effects of groundwater pollution on stems. But
given the wide structural and functional variation in stems, it
is remarkable that this book has so comprehensively covered
their functions and interactions.
Some chapters are very clear and easy to follow, others leave
the reader to fill in gaps. Not all of the authors are clear about
when they speculate. Terminology from several research fields
is used in the text, but many terms are not defined. Defining
more of the terminology would ease reading across disciplines.
TREE PHYSIOLOGY ON-LINE at http://www.heronpublishing.com
604
The chapters by Gartner, Givinish, Holbrook, Nilsen, Pate and
Jeschke, and Weber and Grulke are especially well written and
clear. Some authors clearly state where the most important
areas for future research are, and some emphasize the importance of more research in terms of real-world applications.
As I read the review chapters, I looked forward to a summary
chapter that pulled all of stem biology together, but an entire
second volume would be required to develop a synthesis of the
preceding chapters with one voice. Hinckley and Schulte’s
summary chapter reiterates some of the important concepts
developed in the book, such as redundancy and modularity of
construction, the incorporation of life history into the annual
rings and structure of stems of individual trees, the energy
costs of building disposable and nondisposable stems, responding to environmental signals and communication among
plant organs, difficulties in research on tree stems, interactions
among stem functions and processes, and trade-offs among
and optimization of functional strategies.
The book’s index limits its usefulness for reference. Not all
occurrences of some terms used within the text are listed (e.g.,
integrated physiological unit), and I couldn’t find index entries
for monocotyledons, palms, primary xylem, or vascular bun-
dles----all of which are discussed in various places throughout
the volume. Also, inclusion of taxa in the index, or in a separate
index, would have been very useful.
This book deserves a wide readership. Researchers, graduate students, and advanced undergraduates in any field concerned with plant growth or function will find the book
informative and thought provoking. College teachers and laboratory instructors will be able to glean ideas for student projects from the many suggestions for proposed research.
Referring to the ‘‘wide diversity of perspectives’’ in this volume, Hinckley and Schulte write, ‘‘...we tend to study our small
piece of the stem, but if we are to understand it as an entire
structure we must take this broader view.’’ The next steps are
for botanists, ecologists, and other scientists to read this book,
do the research, and integrate the results among their fields.
Clearly, the black box is being uncloaked----the time for integration and synthesis has arrived!
Ann M. Lewis, Department of Forestry and Wildlife Management, Holdsworth Hall, University of Massachusetts, Amherst,
MA 01003-4210, USA.
TREE PHYSIOLOGY VOLUME 17, 1997