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Book Review |
Department of Biological Science, Florida International University, Miami, Florida 33199 USA
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ABSTRACT |
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 TOP ABSTRACT LITERATURE CITED |
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Is teaching about plants still important and necessary in the 21st century? Stories of low enrollments in basic undergraduate botany courses and the demise of botany departments or botany curricula circulate through the plant science community, causing nail biting and reevaluations. The answer to the question, however, is as close as your next meal, the clothes next to your skin, or your next walk in the woods. Knowledge of how plants grow and where they fit into the world is fundamental to coping with universal problems, such as world nutrition and global warming. In his book Éloge de la Plante (1999) Francis Hallé considers what would happen to the world if all the animals suddenly disappeared as compared to a scenario where all the plants evaporated. Either event would cause immediate changes in what the world is like, but if the animals disappeared, the plants would probably survive, while the converse is not true.
Botanical knowledge also enhances our understanding and appreciation of our world and improves the quality of many people's lives, as the perennial popularity of gardening, garden clubs, and plant interest groups indicates (Crespon et al., 1996
; Bhatti and Church, 2001
).
In addition, the popularity of books such as The Botany of Desire (Pollan, 2001
) illustrates the fascination plants have for the general public.
Given this basic need and interest, as well as the enormous strides being made in our scientific understanding of plant systematics, development and ecology, why are plant scientists worried? Partly, the appeal of plants is not intuitive in the warm fuzzy (or even wet slimy) way that animals are. Plants are an alien life form to us. Although similarities exist biochemically between plants and animals (but then, there is photosynthesis), the cell, tissue, and organ levels of organization and the ecological interactions of plants differ substantially from those of most animals and therefore require more education to understand and appreciate. Perhaps because of this essential strangeness, plant biology is often poorly taught in kindergarten through high school, except that plant immobility and restrictions on the use of animals in experiments means that some aspect of growing plants often crops up in science fair projects. With the increasing concentration of population in urban and suburban environments, our daily interactions with plants are more controlled and less diverse than at any time in the history of humankind, so students arrive at college with less direct experience of plants than in former times. For students who have some knowledge of plants, their awareness often comes from some relative's enjoyment of gardening, or they have experienced the beauty of natural landscapes framed by plants during vacations, school outings, or visits to urban and suburban parks.
How, then, does plant education fare in our universities? An introduction to the plant kingdom is always included in basic undergraduate biology texts (e.g., Purves et al., 2001
; Raven and Johnson, 2002
; and many others). Most of these courses cover photosynthesis and plant morphology, growth, and development. For a person interested in learning about plants, general biology might be followed by an introductory botany course, or, alternatively, students could immediately enroll in more specialized courses, such as plant morphology, systematics, or physiology. In addition, many universities offer nonmajor botany courses to fulfill general science requirements; these assume no scientific background. Traditionally, all of these introductory courses are taught with a textbook. Current books on the market include The Biology of Plants, 6th ed. (Raven, Evert, and Eichhorn, 1999
), Botany—An Introduction to Plant Biology, 2nd ed. (Mauseth, 1998
), Botany, 2nd ed. (Moore, Clark, and Vodopich, 1998
), Plant Biology (Rost et al., 1998
), Introductory Plant Biology (Stern, 1997
), Introductory Botany—Plants, People and the Environment (Berg, 1997
), or Plants and Society (Levetin and McMahon, 1999
). The first five of these are suitable for science majors but try to be accessible to nonmajors, while the last two focus on nonmajors. They all cover plant cells and cell division, plant morphology and anatomy, plant physiology, genetics, plant life cycles, and classification at some level. They all are amply illustrated with color photographs and diagrams, and they all supply computerized test banks and teaching aids, such as overhead transparencies or CD-ROMs and Web site references or tie-ins.
Alternatives to these classical texts that are aimed at nonmajors or at a general audience include books such as Reaching for the Sun (King, 1997
), which explains plant physiology and biochemistry to the interested layperson, and David Attenborough's The Private Life of Plants (Attenborough, 1995
), a self-described "natural history of plant behavior," written in conjunction with an excellent video series of the same name. The books reviewed here are three new contributions to this spectrum of approaches to education about plants.
We personally teach a variety of plant courses at our university, including a large-enrollment nonmajor botany course, a good dose of botany in the two-semester general biology course, upper division courses in tropical botany, plant morphology, economic botany, and the meaning of the garden, as well as graduate courses and workshops in our areas of expertise. Other plant-oriented faculty in our department teach additional courses, so a classical botany curriculum is covered, although we belong to a Department of Biological Sciences. Our courses generally have good enrollments, and we don't see any evidence of the "death" of botany. In evaluating the books covered in this review, we considered the question of what we look for in a textbook against the background of our teaching experiences. The answer to this question, we found, depends on whether the course is for majors, nonmajors, or both; whether the course has a laboratory associated with it; and, of course, the level of the course—lower division, upper division, or graduate. Common considerations are (1) cost, which will affect the possibility of using a second paperback for supplementary ideas; (2) accuracy, adequacy, and accessibility of information, as the depth of treatment and subjects covered will vary between majors and nonmajors; (3) clarity of illustrations, both for the students' understanding and for use of them in lectures; (4) attractiveness of illustrations, which should be high for a subject that has a strong visual appeal; (5) provision of an alternative narrative voice for students to learn from vs. emphasis on the professor's biases in organizing the course, e.g., plant physiology and biochemistry vs. economic uses, ecology, function, etc.; and (6) currency of treatment with respect both to scientific topics and societal concerns. The books reviewed here represent three very different approaches to fulfilling these needs in a text.
Of the three, Plant Life by Ennos and Sheffield is probably the most accessible to the nonmajor. After a brief treatment of basic principles of evolution and of evolutionary history in the first two chapters, the authors provide a survey of the algae (chapters 3, 4), evolution of plants onto land, plus bryophytes and lichens (chapter 5), evolution of vascular plants and fern reproduction (chapter 6), and evolution and reproduction of the seed plants (chapter 7). The final third of the book describes selected aspects of ecology and adaptation for the tropics (chapter 8), seasonal climates (chapter 9), extreme environments, such as deserts and cold habitats (chapter 10), and aquatics (chapter 11). The book has a glossary and an index. There are no references in the text, but there is a brief list of further reading at the end of each chapter that generally refers to other texts. The authors provide a short appendix that goes over general plant classification.
Although the book does not cover many topics typically included in an introductory botany text, such as plant cell biology, physiology, and development, it has a nice choice of topics and selects interesting stories to present within each topic. For example, the discussion of the wet tropics describes lianas, strangler figs, adaptations of epiphytes, including CAM photosynthesis, and rainforest parasites (Rafflesia)—stuff to capture anyone's imagination. The treatment of the bryophytes is especially detailed for a general text. Unfortunately, there are numerous inaccuracies in the details of the material. For example, the authors describe the pine pollen tube digesting its way through the nucellus to the ovule, when the nucellus is part of the ovule (chapter 7, p. 118), or, when comparing monocots and dicots, pictures that look more like seeds are said to be pollen, and the grass coleoptile is labeled as a cotyledon (chapter 7, fig. 7.11, p. 124). In addition, although the use of black-and-white illustrations probably helps to keep the cost low, many of the drawings and photographs are not very clear, apparently having been reduced from originals, and the labeling on them is minimal and often inaccurate (e.g., fig. 3.1, a cross-section of Anabaena, has the thylakoids outside the cell wall). A center insertion of 8 plates has beautiful color photographs, many of which are sharp close-ups with good color. Because they are out of context, however, these photographs don't add very much to the text.
The book has a definite narrative voice and is easy to read. It sometimes uses nontechnical descriptive vocabulary, saying that cyanobacterial mats "can also end up choking the life out of the water" (p. 41) or that bryophytes can't grow "far from their substrate except in a damp mass" (p. 87), but provides what at times is excessive technical detail—e.g., does the audience that this book seems aimed at need to know the details of megasporogenesis? The authors also present grand, speculative generalizations that seem unnecessary and misleading. When discussing rainforest trees, for example, they say that "Because they posses wider, more efficient water-conducting vessels, angiosperm trees do not need such thick trunks for water transport as conifers. They can therefore grow tall much faster and invest relatively more material into productive photosynthetic machinery" (p. 135). We don't know of any evidence comparing trunk diameter of a range of conifers vs. angiosperms standardized for growing conditions and age to support the statement about differences in thickness of trunks; this statement also ignores the differences in numbers of tracheids vs. vessels in conifers and angiosperms, their relative contributions to support (tracheids provide more, vessels less), and their differing susceptibility to embolism (Sperry and Sullivan, 1992
; Sperry et al., 1994
; Zwieniecki and Holbrook, 1998
); there is evidence that some conifers conduct as efficiently as angiosperms at the whole plant level (Becker, Tyree, and Tsuda, 1999
). Finally, the discussions of phylogeny are not consistent with current ideas and molecular evidence (Hoot, Magallon, and Crane, 1999
; Mathews and Donohgue, 1999
; Samigullin et al., 1999), although to some extent this reflects the rapid advances being made in our understanding of basal plant phylogeny (Pryer et al., 2001
). Thus, this book, while accessible to a nonmajors audience and readable, has a enough gaps and errors that you probably wouldn't want to use it as a primary text but might recommend it as a supplementary text for certain courses. At between $40 and $50 for a paperback, however, the price might exclude its use in this category.
Green Plants by Bell and Hemsley is a completely different kind of book. It is a welcome update and improvement on the first edition by Bell and Woodcock (1983
). This is not a book that you would use in a nonmajor course, and it would not be used in most introductory major courses as they are taught today. It is, however, a wonderful introduction to the morphological and physiological diversity and evolution of photosynthetic organisms. This is a book that should be read by students truly interested in plants, botany graduate students studying for their qualifying examinations, and anyone wanting to understand the latest advances in our understanding of the diversity of photosynthetic organisms. It has an original approach to what should be included under the study of green plants, beginning in chapter 1 with a discussion of autotrophy vs. heterotrophy, which leads to consideration of the different kinds of autotrophy and sets the groundwork for the authors to settle on oxygenic photosynthesis as the defining feature of the organisms treated in the book. This approach allows them to describe photosynthetic prokaryotes and algae, as well as land plants, and introduces some comparative biochemistry/physiology, as well as comparative morphology and reproduction.
The organization of the book is taxon-based. It begins with general features of the plant kingdom (chapter 1), proceeds to the prokaryotic and eukaryotic algae (chapters 2, 3, 4), then treats the bryophytes (chapter 5), the evolution of land plants and the fern allies (chapter 6), ferns (chapter 7), gymnosperms (chapter 8), and angiosperms (chapter 9). At its end the book provides a glossary, an index, and concise suggestions for further reading organized by chapter. These suggestions refer to specialized texts or reviews of recent literature. Throughout, the authors provide good coverage of fossil taxa and of recent physiological, structural, and biochemical developments. The book is illustrated with nice line drawings and black-and-white photographs that are clearly and accurately labeled in sufficient detail. The authors use current cladistic and molecular systematic information, incorporating or referring to some of the recent radical changes in plant phylogeny. The book provides good treatments of reproduction and the details of life cycles for all the major groups. Like Sheffield and Ennos, Bell and Hemsley give a more complete treatment of bryophytes than is often seen in introductory texts.
Green Plants has a definite voice and an idiosyncratic approach, seen both in the subjects treated and in things like their critical discussion of the endosymbiont hypothesis. In short, this book is scholarly but very accessible and readable to anyone with an interest in plant diversity. It will serve well as a text or reference for comparative plant biology courses and as a current review for professors teaching any undergraduate beginning course. The paperback price ($31.95) makes it attractive as a supplementary text and reference, if it doesn't fit your requirements for a primary text.
Principles of Botany by Uno, Storey, and Moore represents the most advanced state in the evolution of the American botanical textbook. It differs from the previous two books in scope, for it covers a much broader range of topics and does so in a fair amount of detail. The organization of the book is typical for American undergraduate general/introductory level biology or botany texts. The book has nineteen chapters with an introduction to botany (chapter 1), ecology and natural selection (chapter 2), chemical principles (chapter 3), plant cells and tissues (chapter 4), DNA and cell division (chapter 5), plant development and hormones (chapter 6), root, stem, and leaf structure and function (chapters 7, 8, 9), photosynthesis and respiration (chapters 10, 11), angiosperm reproduction (chapter 12), genetics and evolution (chapters 13, 14), speciation and classification (chapter 15), survey of nonanimal kingdoms (chapters 16, 17, 18), and energy flow, nutrient cycling, and biomes (chapter 19). It provides appendices on genetic engineering and chemistry, a glossary, and an index. At the end of each chapter are suggestions for further readings that include recent articles and books, as well as Website references. The price (approximately $86 paperback) is in the range of comparable texts.
In contrast to the other two books reviewed here, Principles of Botany comes from the lineage of classical botany textbooks currently on the market, and it shares organizational properties with many of these, including a strong emphasis on formal pedagogy and canalization of the learning process. For example, Principles of Botany has a chapter outline and Web references at the beginning of each chapter and a chapter summary at the end of each chapter, followed by "essay questions" and "thought questions." Within each chapter, sections begin with a topic statement in large type on a purple gradient background and end with an "inquiry summary" that summarizes what was said. Subheadings are separated from the rest of the text, are italicized, and make simple statements. Key words and new terms are printed in bold. The text is linked to color-coded asides with signature backgrounds ("Perspectives" on purple palmately lobed leaves, "The Lore of Plants" on uniform aqua, "Tables" in beige and purple simple leaves on pink). The entire book is copiously and beautifully illustrated with color photographs, color diagrams, and line drawings, although many of the illustrations are taken from textbooks previously published by McGraw-Hill. McGraw-Hill provides additional material for teachers, such as a CD-ROM of illustrations from the book, as well as images from other McGraw-Hill botany books, an instructor's manual, test question software, transparencies, and a support service for running a course Website. Thus, the book is modern both in material covered and in how it is supported, integrating on-line resources with print resources and current methods for presenting scientific material.
Despite its comprehensive nature, the book skimps in certain areas; for example, its discussion of development is not strong, especially given the current revolution in our understanding of the genetics of plant development—why give all the details of photosynthesis but not go into the ABC model of floral development (Schwarz-Sommer et al., 1990
; Weigel and Meyerowitz, 1994
; Howell, 1998
)? Some of the material is redundant; for example, much information from the second chapter on evolution is repeated in other chapters later in the text. When using the book for our nonmajors course, we ended up jumping around in the text to provide readings for specific lectures. Because the text is so segmented, however, this is not much more disruptive than reading a chapter straight through.
When considering the utility of this book for majors vs. nonmajors courses, we think that it tries to cover both needs and falls somewhere in between actually doing so. For example, its coverage of photosynthesis and respiration is much too sophisticated for nonmajors, while its coverage of relevant popular topics, such as coffee and psychoactive plants, while better than most general texts, is still a little light.
Principles of Botany, then, is the state-of-art for a general botany textbook, and when adopting a text for your introductory course, of the three books reviewed here, it is probably the book that you would choose. There are some drawbacks, however, to using this text. These drawbacks are general features of modern introductory life sciences textbooks but deserve consideration, as we can imagine alternatives.
Textbooks today are the product of numerous editors, artists, production specialists, and business managers, as well as of the published authors. As such, a textbook such as Principles of Botany reflects the business community's perception of students in American colleges and universities and results from compromises inherent in the processes of professional review and marketing that are part of the team production of textbooks today. These compromises remove the writer's "voice" and any "writerly" continuity. With its emphasis on pedagogy and interesting asides, we find these books too distracting to actually read—the manner of presentation encourages the reader to pick the book up, glance at it, and soon put it down, or to flip through it before the exam, using it as a quick reference. Most teachers who choose such texts probably won't read them, selecting them primarily based on the utility of their diagrams in lectures and the scope of their coverage. An Internet discussion of introductory biology and botany textbooks that evolved from writing this review revealed that many university teachers also do not expect students to read these books, using them, instead, as references.
A "common wisdom" that you hear in academic circles today is that students have a 20-min attention span in the lecture setting. The new teaching techniques moving into the classroom, including inquiry-based and cooperative learning, are partly strategies to break up classroom time into shorter units, and thus, hopefully, to improve retention. This is the "TV generation" model for lecturing—after 20 min, you need a commercial. Principles of Botany, like most modern science texts, seems to be organized around this model for teaching—after a page, you need a human-interest story. This constant interruption of the text makes it hard to follow the main points, necessitating the emphasis on headlines and bold type for important points, but these learning aids create yet more distractions.
We think that this type of organization has some fundamental flaws for teaching biology. The distractions make it hard to establish the logical flow that is part of the beauty of science. As a counterpoint to the TV model, we note that today's students watch movies, as well as TV, and movies require attention spans that might even stretch to 2 hours. Thus, it is not impossible for our students to follow single stories, topics, or ideas for 20 pages. We just need to give them well-written texts that leave them in peace to do so. In addition, subjects may become dull when they are made too obvious and repetitive. Part of the joy of learning is discovery—discovery of what is important or making your mind work to put together ideas or build your own model of what must be going on or create your own way to remember it. A nonmajor can do this equally as well as a major, just in different terms and with different building blocks. The excessive organization of textbooks such as Principles of Botany, even if beautifully done, robs students of some of this mental magic.
Principles of Botany may represent a transition between using print and Web-based resources in teaching introductory courses. In some ways, while incorporating computer-based technology, it doesn't really utilize the unique organizational features of web-based learning to change how we teach. The next step, we think, is to use the flexibility of Internet information presentation and the facility of graphical presentation on the Web to restructure our concept of the textbook. Incorporation of the Web should allow development of printed textbooks that are more personalized, portable, and perhaps more affordable, with the asides, human-interest stories, and supplementary material presented electronically. We envision textbooks becoming a series of separate booklets or "chapters," each in printed text that may include diagrams or a few pictures, but with Web references to supplementary material and graphics. A professor could pick topics (chapters), assemble a "textbook" from this, and tailor his/her textbook to the course being taught. The printed chapters would provide basic material for the subject matter, while the Web would supply illustrations, supplementary material, and more advanced information. This modular approach would let teachers choose the content and level of their textbook, depending on whether they were teaching majors or nonmajors, lower division or upper division. Because textbooks for individual courses could be made to cost more or less by the professor's choices, they could include other books and materials as required reading. Such an approach might also encourage many more individuals to get involved in writing textbook material—the idea of assembling a chapter of a text is much less daunting than the idea of overseeing an entire encyclopedic textbook.
Although the type of textbook used is important in teaching botany, we think that the most important approach is to include lots of hands-on, personal, and direct experience with plants. Because plants are an alien life form for us, understanding them both requires and offers the opportunity for direct observation with our animal prejudices set aside. Modules for future textbooks should enhance this direct experience by including material on local environments and plants, allowing professors to customize their textbooks to the environments in which they teach. The need for this type of unique instruction, where what our students experience is very different from what is taught in most botany textbooks, is something that we experience strongly in south Florida—e.g., many of our students experience legumes as trees rather than as peas or beans. Use of modular Web texts would allow teachers to integrate the background material needed to enhance students' immediate experience.
The requirement for education about plants is not going to go away, as we need to know about plants in order to manage and appreciate our world. As we move into the 21st century, we will continue to need a variety of texts to support our varied approaches to teaching about plants to diverse audiences. The poet Gary Snyder (1974) spoke eloquently and simply to the heart of our need to know about plants in his poem "For the Children":
The rising hills, the slopes,of statistics
lie before us.
the steep climb
of everything, going up,
up, as we all
go down.
In the next century
or the one beyond that,
they say,
are valleys, pastures,
we can meet there in peace
if we make it.
To climb these coming crests
one word to you, to
you and your children:
stay together
learn the flowers
go light
——— by Gary Snyder, from TURTLE ISLAND, copyright ©1974 by Gary Snyder. Reprinted by permission of New Directions Publishing Corp.
Think of this when you wonder about the future of botanical education.
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FOOTNOTES |
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Green plants: their origin and diversity, 2nd ed. P. R. Bell and A. R. Hemsley. Cambridge University Press. 2000. ISBN 0-521-64109-8.
Principles of botany. G. Uno, R. Storey, and R. Moore. McGraw-Hill Higher Education. 2001. ISBN 0-07-228592-3.
The quotation in the title is taken from Blake, W. 1977. "Auguries of Innocence," l. 1–2. In A. Ostriker [ed.], William Blake: the complete poems, 506. Penguin Books, London, England. 
2 The authors of this review would like to acknowledge the help of an Internet discussion among a number of post-secondary teachers on the use of current introductory biology and botany texts. This dialogue focused some of our ideas for this article, and we thank Dr. Leora Baron at the Academy for the Art of Teaching, Florida International University (academy{at}fiu.edu
), for orchestrating it.
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LITERATURE CITED |
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TOPABSTRACTLITERATURE CITED |
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Becker P. M. T. Tyree M. Tsuda 1999 Hydraulic conductances of angiosperms versus conifers: similar transport sufficiency at the whole-plant level. Tree Physiology 19: 445-452[Abstract]
Bell P. R. C. L. F. Woodcock 1983 Diversity of green plants, 3rd ed. Edward Arnold, London, UK
Berg L. R. 1997 Introductory botany: plants, people, and the environment. Saunders College Publishing, Orlando, Florida, USA
Bhatti M. A. Church 2001 Cultivating natures: homes and gardens in late modernity. Sociology 35: 365-383
Crespon C. J. S. J. Keteyian G. W. Heath C. T. Sempos 1996 Leisure-time physical activity among US adults—results from the third national health and nutrition examination survey. Archives of Internal Medicine 156: 93-98
Hallé F. 1999 Éloge de la plante. Editions du Seuil, Paris, France
Hoot S. B. S. Magallon P. R. Crane 1999 Phylogeny of basal eudicots based on three molecular data sets: atpB, rbcL, and 18s nuclear ribosomal DNA sequences. Annals of the Missouri Botanical Garden 86: 1-32
Howell S. H. 1998 Molecular genetics of plant development. Cambrige University Press, Cambridge, UK
King J. 1997 Reaching for the sun: how plants work. Cambridge University Press, Cambridge, UK
Levetin E. K. McMahon 1999 Plants and society, 2nd ed. WCB/McGraw-Hill, Boston, Massachusetts, USA
Mathews S. M. J. Donoghue 1999 The root on angiosperm phylogeny inferred from duplicate phytochrome genes. Science 286: 947-950
Mauseth J. D. 1998 Botany: an introduction to plant biology, 2nd ed. Jones and Bartlett, Sudbury, Massachusetts, USA
Moore R. W. D. Clark D. S. Vodopich 1998 Botany, 2nd ed. WCB/McGraw Hill, Boston, Massachusetts, USA
Pollan M. 2001 The botany of desire: a plant's-eye view of the world. Random House, New York, New York, USA
Pryer K. M. H. Schneider A. R. Smith R. Cranfill P. G. Wolf J. S. Hunt S. D. Sipes 2001 Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants. Nature 409: 618-622[CrossRef][Medline]
Purves W. K. D. Sadava G. H. Orians H. C. Heller 2001 Life: the science of biology, 6th ed. Sinauer Associates, Sunderland, Massachusetts, USA
Raven P. H. R. F. Evert S. E. Eichhorn 1999 Biology of plants, 6th ed. W.H. Freeman/Worth, New York, New York, USA
Raven P. H. G. B. Johnson 2002 Biology, 6th ed. McGraw-Hill, New York, New York, USA
Rost T. L. M. G. Barbour C. R. Stocking T. M. Murphy 1998 Plant biology. Wadsworth, Belmont, California, USA
Samigullin T. K. W. F. Martin A. V. Troitsky A. S. Antonov 1999 Molecular data from the chloroplast rpoC1 gene suggest a deep and distinct dichotomy of contemporary spermatophytes into two monophyla: gymnosperms (including gnetales) and angiosperms. Journal of Molecular Evolution 49: 310-315[CrossRef][Web of Science][Medline]
Schwarz-Sommer Z. P. Huijser W. Nacken H. Saedler H. Sommer 1990 Genetic control of flower development by homeotic genes in Antirrhinum majus. Science 250: 931-936
Snyder G. 1974 Turtle Island. New Directions Books, New York, New York, USA
Sperry J. S. K. L. Nichols J. E. M. Sullivan S. E. Eastlack 1994 Xylem embolism in ring-porous, diffuse-porous, and coniferous trees of northern Utah and interior Alaska. Ecology 75: 1736-1752[CrossRef][Web of Science]
Sperry J. S. J. E. M. Sullivan 1992 Xylem embolism in response to freeze-thaw cycles and water-stress in ring-porous, diffuse-porous, and conifer species. Plant Physiology 100: 605-613
Stern K. R. 1997 Introductory plant biology, 7th ed. Wm. C. Brown, Dubuque, Iowa, USA
Weigel D. E. M. Meyerowitz 1994 The ABCs of floral homeotic genes. Cell 78: 203-209[CrossRef][Web of Science][Medline]
Zwieniecki M. A. N. M. Holbrook 1998 Diurnal variation in xylem hydraulic conductivity in white ash (Fraxinus americana L.), red maple (Acer rubrum L.) and red spruce (Picea rubens Sarg.). Plant, Cell and Environment 21: 1173-1180[CrossRef]
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