magill™s encyclopedia of science -...

MAGILLS ENCYCLOPEDIA OF SCIENCE

P L A N T L I F E

MAGILLS ENCYCLOPEDIA OF SCIENCE

P L A N T L I F E

Volume 3Microbial Nutrition and Metabolism–Sustainable Agriculture

EditorBryan D. Ness, Ph.D.Pacific Union College, Department of Biology

Project EditorChristina J. Moose

Salem Press, Inc.Pasadena, CaliforniaHackensack, New Jersey

Copyright © 2003, by Salem Press, Inc.All rights in this book are reserved. No part of this work may be used or reproduced in any manner what-

soever or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording,or any information storage and retrieval system, without written permission from the copyright ownerexcept in the case of brief quotations embodied in critical articles and reviews. For information address thepublisher, Salem Press, Inc., P.O. Box 50062, Pasadena, California 91115.

Some of the updated and revised essays in this work originally appeared in Magill’s Survey of Science: LifeScience (1991), Magill’s Survey of Science: Life Science, Supplement (1998), Natural Resources (1998), Encyclopediaof Genetics (1999), Encyclopedia of Environmental Issues (2000), World Geography (2001), and Earth Science (2001).

∞ The paper used in these volumes conforms to the American National Standard for Permanence ofPaper for Printed Library Materials, Z39.48-1992 (R1997).

Library of Congress Cataloging-in-Publication Data

Magill’s encyclopedia of science : plant life / edited by Bryan D. Ness.

p. cm.Includes bibliographical references (p. ).

ISBN 1-58765-084-3 (set : alk. paper) — ISBN 1-58765-085-1 (vol. 1 : alk. paper) —ISBN 1-58765-086-X (vol. 2 : alk. paper) — ISBN 1-58765-087-8 (vol. 3 : alk. paper) —ISBN 1-58765-088-6 (vol. 4 : alk. paper)

1. Botany—Encyclopedias. I. Ness, Bryan D.QK7 .M34 2002580′.3—dc21

2002013319

First Printing

printed in the united states of america

Editor in Chief: Dawn P. DawsonManaging Editor: Christina J. Moose

Manuscript Editor: Elizabeth Ferry SlocumAssistant Editor: Andrea E. MillerResearch Supervisor: Jeffry Jensen

Acquisitions Editor: Mark Rehn

Photograph Editor: Philip BaderProduction Editor: Joyce I. BucheaPage Design and Graphics: James HutsonLayout: William ZimmermanIllustrator: Kimberly L. Dawson Kurnizki

TABLE OF CONTENTS

List of Illustrations, Charts, and Tables . . . . xlixAlphabetical List of Contents . . . . . . . . . . liii

Microbial nutrition and metabolism . . . . . . 663Microbodies . . . . . . . . . . . . . . . . . . . . 666Microscopy . . . . . . . . . . . . . . . . . . . . 668Mitochondria . . . . . . . . . . . . . . . . . . . 672Mitochondrial DNA . . . . . . . . . . . . . . . 675Mitosis and meiosis . . . . . . . . . . . . . . . 677Mitosporic fungi . . . . . . . . . . . . . . . . . 681Model organisms . . . . . . . . . . . . . . . . . 682Molecular systematics . . . . . . . . . . . . . . 686Monocots vs. dicots . . . . . . . . . . . . . . . 688Monocotyledones . . . . . . . . . . . . . . . . . . 690Monoculture . . . . . . . . . . . . . . . . . . . 692Mosses . . . . . . . . . . . . . . . . . . . . . . . 694Multiple-use approach . . . . . . . . . . . . . . 697Mushrooms . . . . . . . . . . . . . . . . . . . . 699Mycorrhizae. . . . . . . . . . . . . . . . . . . . 702

Nastic movements . . . . . . . . . . . . . . . . 704Nitrogen cycle . . . . . . . . . . . . . . . . . . 706Nitrogen fixation . . . . . . . . . . . . . . . . . 709Nonrandom mating . . . . . . . . . . . . . . . 712North American agriculture. . . . . . . . . . . 714North American flora . . . . . . . . . . . . . . 718Nuclear envelope . . . . . . . . . . . . . . . . . 722Nucleic acids . . . . . . . . . . . . . . . . . . . 723Nucleolus . . . . . . . . . . . . . . . . . . . . . 727Nucleoplasm . . . . . . . . . . . . . . . . . . . 729Nucleus . . . . . . . . . . . . . . . . . . . . . . 730Nutrient cycling . . . . . . . . . . . . . . . . . 732Nutrients . . . . . . . . . . . . . . . . . . . . . 734Nutrition in agriculture . . . . . . . . . . . . . 737

Oil bodies . . . . . . . . . . . . . . . . . . . . . 740Old-growth forests . . . . . . . . . . . . . . . . 741Oomycetes. . . . . . . . . . . . . . . . . . . . . 743Orchids . . . . . . . . . . . . . . . . . . . . . . 745

Organic gardening and farming . . . . . . . . 747Osmosis, simple diffusion, and

facilitated diffusion . . . . . . . . . . . . . . 751Oxidative phosphorylation . . . . . . . . . . . 755Ozone layer and ozone hole debate . . . . . . 757

Pacific Island agriculture . . . . . . . . . . . . 761Pacific Island flora . . . . . . . . . . . . . . . . 765Paclitaxel . . . . . . . . . . . . . . . . . . . . . 768Paleobotany . . . . . . . . . . . . . . . . . . . . 770Paleoecology . . . . . . . . . . . . . . . . . . . 774Parasitic plants . . . . . . . . . . . . . . . . . . 777Peat. . . . . . . . . . . . . . . . . . . . . . . . . 779Peroxisomes . . . . . . . . . . . . . . . . . . . . 782Pesticides . . . . . . . . . . . . . . . . . . . . . 783Petrified wood . . . . . . . . . . . . . . . . . . 787Pheromones . . . . . . . . . . . . . . . . . . . . 790Phosphorus cycle . . . . . . . . . . . . . . . . . 791Photoperiodism. . . . . . . . . . . . . . . . . . 794Photorespiration . . . . . . . . . . . . . . . . . 796Photosynthesis . . . . . . . . . . . . . . . . . . 800Photosynthetic light absorption. . . . . . . . . 804Photosynthetic light reactions. . . . . . . . . . 807Phytoplankton . . . . . . . . . . . . . . . . . . 809Pigments in plants . . . . . . . . . . . . . . . . 812Plant biotechnology . . . . . . . . . . . . . . . 815Plant cells: molecular level . . . . . . . . . . . 821Plant domestication and breeding . . . . . . . 826Plant fibers . . . . . . . . . . . . . . . . . . . . 829Plant life spans . . . . . . . . . . . . . . . . . . 831Plant science. . . . . . . . . . . . . . . . . . . . 835Plant tissues . . . . . . . . . . . . . . . . . . . . 839Plantae . . . . . . . . . . . . . . . . . . . . . . . 843Plants with potential . . . . . . . . . . . . . . . 849Plasma membranes. . . . . . . . . . . . . . . . 851Plasmodial slime molds . . . . . . . . . . . . . 854Poisonous and noxious plants . . . . . . . . . 857Pollination. . . . . . . . . . . . . . . . . . . . . 862Polyploidy and aneuploidy . . . . . . . . . . . 865

xlvii

Population genetics . . . . . . . . . . . . . . . 868Prokaryotes . . . . . . . . . . . . . . . . . . . . 870Proteins and amino acids . . . . . . . . . . . . 873Protista . . . . . . . . . . . . . . . . . . . . . . . 875Psilotophytes . . . . . . . . . . . . . . . . . . . 879

Rain-forest biomes . . . . . . . . . . . . . . . . 883Rain forests and the atmosphere . . . . . . . . 885Rangeland . . . . . . . . . . . . . . . . . . . . . 889Red algae . . . . . . . . . . . . . . . . . . . . . 892Reforestation . . . . . . . . . . . . . . . . . . . 894Reproduction in plants. . . . . . . . . . . . . . 897Reproductive isolating

mechanisms . . . . . . . . . . . . . . . . . . 899Resistance to plant diseases . . . . . . . . . . . 901Respiration . . . . . . . . . . . . . . . . . . . . 904Rhyniophyta . . . . . . . . . . . . . . . . . . . . 907Ribosomes . . . . . . . . . . . . . . . . . . . . . 909Rice. . . . . . . . . . . . . . . . . . . . . . . . . 912RNA . . . . . . . . . . . . . . . . . . . . . . . . 914Root uptake systems . . . . . . . . . . . . . . . 917Roots . . . . . . . . . . . . . . . . . . . . . . . . 920Rubber . . . . . . . . . . . . . . . . . . . . . . . 925Rusts . . . . . . . . . . . . . . . . . . . . . . . . 929

Savannas and deciduous tropical forests . . . 932Seedless vascular plants . . . . . . . . . . . . . 934Seeds . . . . . . . . . . . . . . . . . . . . . . . . 937Selection . . . . . . . . . . . . . . . . . . . . . . 941Serpentine endemism . . . . . . . . . . . . . . 943Shoots . . . . . . . . . . . . . . . . . . . . . . . 944Slash-and-burn agriculture . . . . . . . . . . . 946Soil . . . . . . . . . . . . . . . . . . . . . . . . . 949Soil conservation . . . . . . . . . . . . . . . . . 955Soil contamination . . . . . . . . . . . . . . . . 957Soil degradation . . . . . . . . . . . . . . . . . 959Soil management . . . . . . . . . . . . . . . . . 962Soil salinization . . . . . . . . . . . . . . . . . . 963South American agriculture . . . . . . . . . . . 965South American flora . . . . . . . . . . . . . . 969Species and speciation . . . . . . . . . . . . . . 973Spermatophyta . . . . . . . . . . . . . . . . . . . 976Spices . . . . . . . . . . . . . . . . . . . . . . . 977Stems. . . . . . . . . . . . . . . . . . . . . . . . 980Strip farming . . . . . . . . . . . . . . . . . . . 983Stromatolites . . . . . . . . . . . . . . . . . . . 985Succession . . . . . . . . . . . . . . . . . . . . . 988Sugars . . . . . . . . . . . . . . . . . . . . . . . 991Sustainable agriculture. . . . . . . . . . . . . . 993

xlviii

Magill’s Encyclopedia of Science: Plant Life

PUBLISHER’S NOTE

Magill’s Encyclopedia of Science: Plant Life is de-signed to meet the needs of college and high schoolstudents as well as nonspecialists seeking generalinformation about botany and related sciences. Thedefinition of “plant life” is quite broad, covering therange from molecular to macro topics: the basics ofcell structure and function, genetic and photosyn-thetic processes, evolution, systematics and classi-fication, ecology and environmental issues, andthose forms of life—archaea, bacteria, algae, andfungi—that, in addition to plants, are traditionallystudied in introductory botany courses. A numberof practical and issue-oriented topics are covered aswell, from agricultural, economic, medicinal, andcultural uses of plants to biomes, plant-related en-vironmental issues, and the flora of major regionsof the world. (Readers should note that, althoughcultural and medicinal uses of plants are occasion-ally addressed, this encyclopedia is intended forbroad information and educational purposes.Those interested in the use of plants to achievenutritive or medicinal benefits should consult aphysician.)

Altogether, the four volumes of Plant Life survey379 topics, alphabetically arranged from Acid pre-cipitation to Zygomycetes. For this publication, 196essays have been newly acquired, and 183 essaysare previously published essays whose contentswere reviewed and deemed important to include ascore topics. The latter group originally appeared inthe following Salem publications: Magill’s Survey ofScience: Life Science (1991), Magill’s Survey of Science:Life Science, Supplement (1998), Natural Resources(1998), Encyclopedia of Genetics (1999), Encyclope-dia of Environmental Issues (2000), World Geography(2001), and Earth Science (2001). All of these previ-ously published essays have been thoroughly scru-tinized and updated by the set’s editors. In additionto updating the text, the editors have added newbibliographies at the ends of all articles.

New appendices, providing essential researchtools for students, have been acquired as well:

• a “Biographical List of Botanists” with briefdescriptions of the contributions of 134 fa-mous naturalists, botanists, and other plantscientists

• a Plant Classification table

• a Plant Names appendix, alphabetized bycommon name with scientific equivalents

• another Plant Names appendix, alphabetizedby scientific name with common equivalents

• a “Time Line” of advancements in plant sci-ence (a discursive textual history is also pro-vided in the encyclopedia-proper)

• a Glossary of 1,160 terms

• a Bibliography, organized by category of re-search

• a list of authoritative Web sites with theirsponsors, URLs, and descriptions

Every essay is signed by the botanist, biologist,or other expert who wrote it; where essays havebeen revised or updated, the name of the updaterappears as well. In the tradition of Magill reference,each essay is offered in a standard format that al-lows readers to predict the location of core informa-tion and to skim for topics of interest: The title ofeach article lists the topic as it is most likely to belooked up by students; the “Category” line indi-cates pertinent scientific subdiscipline(s) or area(s)of research; and a capsule “Definition” of the topicfollows. Numerous subheads guide the reader

vii

through the text; moreover, key concepts are itali-cized throughout. These features are designed tohelp students navigate the text and identify pas-sages of interest in context. At the end of each essayis an annotated list of “Sources for Further Study”:print resources, accessible through most libraries,for additional information. (Web sites are reservedfor their own appendix at the end of volume 4.) A“See also” section closes every essay and refersreaders to related essays in the set, thereby linkingtopics that, together, form a larger picture. For ex-ample, since all components of the plant cell arecovered in detail in separate entries (from the Cellwall through Vacuoles), the “See also” sections forthese dozen or so essays list all other essays cover-ing parts of the cell as well as any other topics of in-terest.

Approximately 150 charts, sidebars, maps, ta-bles, diagrams, graphs, and labeled line drawingsoffer the essential visual content so important tostudents of the sciences, illustrating such core con-cepts as the parts of a plant cell, the replicationof DNA, the phases of mitosis and meiosis, theworld’s most important crops by region, the partsof a flower, major types of inflorescence, or differentclassifications of fruits and their characteristics. Inaddition, nearly 200 black-and-white photographsappear throughout the text and are captioned tooffer examples of the important phyla of plants,parts of plants, biomes of plants, and processes ofplants: from bromeliads to horsetails to wheat; fromArctic tundra to rain forests; from anthers to stemsto roots; from carnivorous plants to tropisms.

Reference aids are carefully designed to alloweasy access to the information in a variety of modes:The front matter to each of the four volumes in-

cludes the volume’s contents, followed by a full“Alphabetical List of Contents” (of all the volumes).All four volumes include a “List of Illustrations,Charts, and Tables,” alphabetized by key term, toallow readers to locate pages with (for example)a picture of the apparatus used in the Miller-UreyExperiment, a chart demonstrating the genetic off-spring of Mendel’s Pea Plants, a map showing theworld’s major zones of Desertification, a cross-section of Flower Parts, or a sampling of the manytypes of Leaf Margins. At the end of volume 4 isa “Categorized Index” of the essays, organizedby scientific subdiscipline; a “Biographical Index,”which provides both a list of famous personagesand access to discussions in which they figureprominently; and a comprehensive “Subject Index”including not only the personages but also the coreconcepts, topics, and terms discussed throughoutthese volumes.

Reference works such as Magill’s Encyclopediaof Science: Plant Life would not be possible withoutthe help of experts in botany, ecology, environmen-tal, cellular, biological, and other life sciences; thenames of these individuals, along with their aca-demic affiliations, appear in the front matter tovolume 1. We are particularly grateful to the pro-ject’s editor, Bryan Ness, Ph.D., Professor of Biol-ogy at Pacific Union College in Angwin, California.Dr. Ness was tireless in helping to ensure thorough,accurate, and up-to-date coverage of the content,which reflects the most current scientific knowl-edge. He guided the use of commonly acceptedterminology when describing plant life processes,helping to make Magill’s Encyclopedia of Science:Plant Life easy for readers to use for reference tocomplement the standard biology texts.

viii


CONTRIBUTOR LIST

About the Editor: Bryan Ness is a full professor in the Department of Biology at Pacific Union College, afour-year liberal arts college located atop Howell Mountain in the Napa Valley, about ninety miles north ofSan Francisco. He received his Ph.D. in Botany from Washington State University. His doctoral work focusedon molecular plant systematics and evolution. In addition to authoring or coauthoring a number of scientificpapers, he has contributed to The Jepson Manual: Higher Plants of California, The Flora of North America, amultivolume guide to the higher plants of North America, and more than a dozen articles for various SalemPress publications, including Aging, Encyclopedia of Genetics, Magill’s Encyclopedia of Science: Animal Life,Magill’s Medical Guide, and World Geography. For four years he managed The Botany Site, a popular Internetsite on botany. He is currently working on a book about plant myths and misunderstandings.

Stephen R. AddisonUniversity of Central Arkansas

Richard AdlerUniversity of Michigan, Dearborn

Steve K. AlexanderUniversity of Mary Hardin-Baylor

Michael C. AmspokerWestminster College

Michele ArduengoIndependent Scholar

Richard W. ArnsethScience Applications International

J. Craig BaileyUniversity of North Carolina,

Wilmington

Anita Baker-BlockerApplied Meteorological Services

Iona C. BaldridgeLubbock Christian University

Richard BeckwittFramingham State College

Cindy BenningtonStetson University

Alvin K. BensonUtah Valley State College

Margaret F. BoorsteinC. W. Post College of Long Island

University

P. E. BostickKennesaw State College

J. Bradshaw-RouseIndependent Scholar

Thomas M. BrennanDickinson College

Alan BrownLivingston University

Kenneth H. BrownNorthwestern Oklahoma State

University

Bruce BruntonJames Madison University

Pat CalieEastern Kentucky University

James J. CampanellaMontclair State University

William J. CampbellLouisiana Tech University

Steven D. CareyUniversity of Mobile

Roger V. CarlsonJet Propulsion Laboratory

Robert E. CarverUniversity of Georgia

Richard W. Cheney, Jr.Christopher Newport University

John C. ClauszCarroll College

Miriam ColellaLehman College

William B. CookMidwestern State University

J. A. CooperIndependent Scholar

Alan D. CopseyCentral University of Iowa

Joyce A. CorbanWright State University

Mark S. CoyneUniversity of Kentucky

Stephen S. DaggettAvila College

William A. DandoIndiana State University

ix

James T. DawsonPittsburg State University

Albert B. DickasUniversity of Wisconsin

Gordon Neal DiemADVANCE Education and

Development Institute

David M. DiggsCentral Missouri State University

John P. DiVincenzoMiddle Tennessee State University

Gary E. DolphIndiana University, Kokomo

Allan P. DrewSUNY, College of Environmental

Science and Forestry

Frank N. EgertonUniversity of Wisconsin, Parkside

Jessica O. EllisonClarkson University

Cheryld L. EmmonsAlfred University

Frederick B. EssigUniversity of South Florida

Danilo D. FernandoSUNY, College of Environmental

Science and Forestry

Mary C. FieldsMedical University of South Carolina

Randy FirstmanCollege of the Sequoias

Roberto GarzaSan Antonio College

Ray P. GerberSaint Joseph’s College

Soraya GhayourmaneshIndependent Scholar

Carol Ann GillespieGrove City College

Nancy M. GordonIndependent Scholar

D. R. GossettLouisiana State University,

Shreveport

Hans G. GraetzerSouth Dakota State University

Jerry E. GreenMiami University

Joyce M. HardinHendrix College

Linda HartUniversity of Wisconsin, Madison

Thomas E. HemmerlyMiddle Tennessee State University

Jerald D. HendrixKennesaw State College

John S. HeywoodSouthwest Missouri State University

Jane F. HillIndependent Scholar

Joseph W. HintonIndependent Scholar

Carl W. HoagstromOhio Northern University

Virginia L. HodgesNortheast State Technical Community

College

David Wason Hollar, Jr.Rockingham Community College

Howard L. HosickWashington State University

Kelly HowardIndependent Scholar

John L. HowlandBowdoin College

M. E. S. HudspethNorthern Illinois University

Samuel F. HuffmanUniversity of Wisconsin, River Falls

Diane White HusicEast Stroudsburg University

Domingo M. JarielLouisiana State University, Eunice

Karen N. KählerIndependent Scholar

Sophien KamounOhio State University

Manjit S. KangLouisiana State University

Susan J. KarcherPurdue University

Jon E. KeeleyOccidental College

Leigh Husband KimmelIndependent Scholar

Samuel V. A. KisseadooHampton University

Kenneth M. KlemowWilkes University

Jeffrey A. KnightMount Holyoke College

Denise KnotwellIndependent Scholar

James KnotwellWayne State College

Lisa A. LambertChatham College

Craig R. LandgrenMiddlebury College

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John C. LandoltShepherd College

David M. LawrenceJohn Tyler Community College

Mary Lee S. LedbetterCollege of the Holy Cross

Donald H. LesUniversity of Connecticut

Larry J. LittlefieldOklahoma State University

John F. LogueUniversity of South Carolina, Sumter

Alina C. LopoUniversity of California, Riverside

Yiqi LuoUniversity of Oklahoma

Fai MaUniversity of California, Berkeley

Jinshuang MaArnold Arboretum of Harvard

University Herbaria

Zhong MaPennsylvania State University

Dana P. McDermottIndependent Scholar

Paul MaddenHardin-Simmons University

Lois N. MagnerPurdue University

Lawrence K. MagrathUniversity of Science and Arts of

Oklahoma

Nancy Farm MännikköIndependent Scholar

Sergei A. MarkovMarshall University

John S. MechamTexas Tech University

Roger D. MeicenheimerMiami University, Ohio

Ulrich MelcherOklahoma State University

Iain MillerWright State University

Jeannie P. MillerTexas A&M University

Randall L. MilsteinOregon State University

Eli C. MinkoffBates College

Richard F. ModlinUniversity of Alabama, Huntsville

Thomas J. MontagnoSimmons College

Thomas C. MoonCalifornia University of Pennsylvania

Randy MooreWright State University

Christina J. MooseIndependent Scholar

J. J. MuchovejFlorida A&M University

M. MustoeIndependent Scholar

Jennifer Leigh MykaBrescia University

Mysore NarayananMiami University

Bryan NessPacific Union College

Brian J. NichelsonU.S. Air Force Academy

Margaret A. OlneyColorado College

Oghenekome U. OnokpiseFlorida A&M University

Oluwatoyin O. OsunsanyaMuskingum College

Henry R. OwenEastern Illinois University

Robert J. ParadowskiRochester Institute of Technology

Bimal K. PaulKansas State University

Robert W. PaulSt. Mary’s College of Maryland

Kenneth A. PidcockWilkes College

Rex D. PieperNew Mexico State University

George R. PlitnikFrostburg State University

Bernard Possidente, Jr.Skidmore College

Carol S. RadfordMaryville University, St. Louis

V. RaghavanOhio State University

Ronald J. RavenState University of New York

at Buffalo

Darrell L. RayUniversity of Tennessee, Martin

Judith O. RebachUniversity of Maryland,

Eastern Shore

David D. ReedMichigan Technological University

xi

Contributor List

Mariana Louise RhoadesSt. John Fisher College

Connie RizzoPace University

Harry RoyRensselaer Polytechnic Institute

David W. RudgeWestern Michigan University

Neil E. SalisburyUniversity of Oklahoma

Helen SalmonUniversity of Guelph

Lisa M. SardiniaPacific University

Elizabeth D. SchaferIndependent Scholar

David M. SchlomCalifornia State University,

Chico

Matthew M. SchmidtSUNY, Empire State College

Harold J. SchreierUniversity of Maryland

John Richard SchrockEmporia State University

Guofan ShaoPurdue University

Jon P. ShoemakerUniversity of Kentucky

John P. ShontzGrand Valley State University

Nancy N. ShontzGrand Valley State University

Beryl B. SimpsonUniversity of Texas

Sanford S. SingerUniversity of Dayton

Susan R. SingerCarleton College

Robert A. SinnottArizona Agribusiness and Equine

Center

Elizabeth SlocumIndependent Scholar

Dwight G. SmithConnecticut State University

Roger SmithIndependent Scholar

Douglas E. SoltisUniversity of Florida

Pamela S. SoltisIndependent Scholar

F. Christopher SowersWilkes Community College

Alistair SponselImperial College

Valerie M. SponselUniversity of Texas, San Antonio

Steven L. StephensonFairmont State College

Dion StewartAdams State College

Toby R. StewartIndependent Scholar

Ray StrossState University of New York at Albany

Susan Moyle StudlarWest Virginia University

Ray SumnerLong Beach City College

Marshall D. SundbergEmporia State University

Frederick M. SurowiecIndependent Scholar

Paris SvoronosQueen’s College, City University

of New York

Charles L. VigueUniversity of New Haven

James WaddellUniversity of Minnesota, Waseca

William J. WassermanSeattle Central Community College

Robert J. WellsSociety for Technical Communication

Yujia WengNorthwest Plant Breeding Company

P. Gary WhiteWestern Carolina University

Thomas A. WikleOklahoma State University

Donald Andrew WileyAnne Arundel Community College

Robert R. WiseUniversity of Wisconsin, Oshkosh

Stephen L. WolfeUniversity of California, Davis

Ming Y. ZhengGordon College

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LIST OF ILLUSTRATIONS, CHARTS, AND TABLES

Volume-pageAcid Precipitation pH Scale (bar graph). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-3Africa, Desertification of (map) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-301African Countries with More than 15 Percent Arable Land, Leading Agricultural Crops of (table) . . . I-15African Rain Forests (Sidebar) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-884Africa’s Agricultural Products (map) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-13Air Pollutant Emissions by Pollutant and Source, 1998 (table) . . . . . . . . . . . . . . . . . . . . . . . . I-45Algae, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-49Algae, Types of (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-48Angiosperm, Life Cycle of an (drawing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-66Angiosperms and Continental Drift (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-63Antibiotic Resistance, The Growth of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-122Ants and Acacias (sidebar). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-254Asian Countries with More than 15 Percent Arable Land, Leading Agricultural Crops of (table) . . . . I-93Australia, Selected Agricultural Products of (map) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-103

Bacillus thuringiensis and Bacillus popilliae as Microbial Biocontrol Agents (table) . . . . . . . . . . . . . I-155Bacterial Diseases of Plants, Some (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-115Biomes and Their Features (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-148Biomes of the World (map) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-151Biomes (percentages), Terrestrial (pie chart) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-152Brown Algae (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-165

Cacao: The Chocolate Bean (sidebar) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-211Carbon Cycle, The (flow chart) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-184Carnivorous Plants (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-194Cell, Parts of a Plant (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-822Cell, Parts of the Plant (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-286Central America, Selected Agricultural Products of (map) . . . . . . . . . . . . . . . . . . . . . . . . . I-208Central American Countries, Leading Agricultural Crops of (table) . . . . . . . . . . . . . . . . . . . . I-209Chromosome, Schematic of a (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-229Conifer Leaves (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-270Conifers, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-271Corn-Producing Countries, 1994, Leading (bar graph) . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-275Crop Yields, Declining with Successive Harvests on Unfertilized Tropical Soils (bar graph). . . . . . III-948Crops and Places of Original Cultivation, Major (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-26Crops of African Countries with More than 15 Percent Arable Land (table) . . . . . . . . . . . . . . . . I-15Crops of Asian Countries with More than 15 Percent Arable Land (table) . . . . . . . . . . . . . . . . . I-93Crops of Central American Countries (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-209Crops of European Countries with More than 20 Percent Arable Land (table) . . . . . . . . . . . . . . II-387Crops of Pacific Island Nations (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-763Cycads, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-283

xiii

Darwin and the Beagle, Charles (sidebar/map) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-402Deforestation, Results of (flow chart) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-295Deforestation by Country, 1990-1995, Percentage of Annual (map). . . . . . . . . . . . . . . . . . . . . I-294Desertification of Africa (map) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-301Diatoms (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-308Dicot (Eudicot) Families, Common (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-74Dinoflagellates (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-312Diseases, Symptoms of Plant (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-314DNA, The Structure of (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-323DNA Replication, Stages in (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-330Drought, Impacts of (sidebar). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-336

Endangered Plant Species, A Sampling of the World’s (table) . . . . . . . . . . . . . . . . . . . . . . . II-352Endocytosis (drawing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-356Endomembrane System, The (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-359Eudicot (Dicot) Families Common in North America (table) . . . . . . . . . . . . . . . . . . . . . . . . II-376Eukarya, Classification of Domain (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1106Eukaryotic Cell, Parts of a (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-383Europe, Selected Agricultural Products of (map) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-386European Countries with More than 20 Percent Arable Land, Leading Agricultural

Crops of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-387Evolution of Plants (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-411Exocytosis (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-357

Ferns, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-420Flower, Parts of a (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-429Flower Shapes: Perianth Forms (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-433Flower Structure, Variations in (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-430Forest Areas by Region (pie chart) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-455Forest Loss in Selected Developing Countries, 1980-1990 (bar graph) . . . . . . . . . . . . . . . . . . . I-296Fruit Types (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-465Fruit Types and Characteristics (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-466Fungi: Phyla and Characteristics (table). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-472

Garden Plants and Places of Original Cultivation (table) . . . . . . . . . . . . . . . . . . . . . . . . . . II-475Genetically Modified Crop Plants Unregulated by the U.S. Department of Agriculture (table) . . . . II-496Germination of a Seed (drawing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-510Ginkgophyta, Classification of Phylum (table). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-513Gnetophytes, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-518Grasses of the United States, Common (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-523Greenhouse Effect (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-535Greenhouse Gas Emissions, 1990-1999, U.S. (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-536Growth Habits (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-542Gymnosperms, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-544

Hormones and Their Functions, Plant (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-575Hornworts, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-579

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Horsetails, Classification of (table). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-581Hydrologic Cycle (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-594

Inflorescences, Some Common (drawing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-601Invasive Plants: Backyard Solutions (sidebar) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-606

Land Used for Agriculture by Country, 1980-1994, Increases in (map) . . . . . . . . . . . . . . . . . . . I-38Leading Peat-Producing Countries, 1994 (bar graph) . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-780Leaf, Parts of a (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-617Leaf Arrangements, Common (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-620Leaf Bases (drawing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-626Leaf Lobing and Division, Common Patterns of (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . II-623Leaf Margins (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-624Leaf Shapes, Common (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-628Leaf Tips (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-625Leaf Tissue, Cross-Section of (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-618Leaves, Types of (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-622Liverworts, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-641Lumber Consumption, U.S. (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1062Lycophytes, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-646

Meiosis: Selected Phases (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-679Mendel’s Pea-Plant Experiments, Results of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-501Mendel’s Pea Plants (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-500Miller-Urey Experiment (drawing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-405Mitochondrion, Structure of a (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-673Mitosis (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-678Monocot Families, Common (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-73Monocot Families Common in North America (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . III-690Monocots vs. Dicots, Characteristics of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-688Mosses, Classification of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-695

Nastic Movement (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-704Nitrogen Cycle (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-707No-Tillage States, 1994-1997 (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-369North America, Selected Agricultural Products of (map) . . . . . . . . . . . . . . . . . . . . . . . . . III-715Nutrients, Plant (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-735

Osmosis, Process of (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-752Ovule, Parts of an (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-70Ozone Hole, 1980-2000, Average Size of the (graph) . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-758

Pacific Island Nations, Leading Agricultural Crops of (table) . . . . . . . . . . . . . . . . . . . . . . . III-763Persons Chronically Undernourished in Developing Countries by Region,

Number of (bar graph) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-39Phosphorus Cycle, The (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-792

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Photoperiodism (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-794Photosynthesis (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-801Plant, Parts of a (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-840Plantae, Phyla of Kingdom (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-844Poisonous Plants and Fungi, Common (table). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-858Pollination (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-864Population Growth, 1950-2020, World and Urban (bar graph) . . . . . . . . . . . . . . . . . . . . . . . II-587Prokaryotic Cell, A (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-871Protista, Phyla of (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-876

Rain Forests, African (Sidebar) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-884Rice-Producing Countries, 1994 (bar graph) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-913Root, Parts of a (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-921Root Systems, Two (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-923Roots, Water Uptake by (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-637Rubber, End Uses of Natural (pie chart) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-928

Seed, Germination of a (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-510Seedless Vascular Plants: Phyla and Characteristics (table) . . . . . . . . . . . . . . . . . . . . . . . . III-935Seeds: Eudicots vs. Monocots (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-938Seeds of Dissent (sidebar) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-497Shoot, Parts of the (drawing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-945Silvicultural Methods, Environmental Effects of Select (flow chart) . . . . . . . . . . . . . . . . . . . . II-452Soap and Water (sidebar). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-123Soil Horizons (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-950Soil Limits to Agriculture, by Percentage of Total Land Area (pie chart) . . . . . . . . . . . . . . . . . III-961Soil Orders in the U.S. Classification System, The Twelve (table) . . . . . . . . . . . . . . . . . . . . . III-952South America, Selected Agricultural Products of (map) . . . . . . . . . . . . . . . . . . . . . . . . . III-966Stem Structure (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1018

Time Line of Plant Biotechnology (table). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-816Tissues, Plant (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-842Transformation of Sunlight into Biochemical Energy (flow chart) . . . . . . . . . . . . . . . . . . . . . II-365Transport Across Cell Membranes, Mechanisms for (table) . . . . . . . . . . . . . . . . . . . . . . . . III-852Tropical Soils, Declining Crop Yields with Successive Harvests on Unfertilized (bar graph). . . . . . III-948Tropisms (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1028

Water Through a Plant, The Path of (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1049Water Uptake by Roots (drawing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-637Welwitschia: The Strangest Gymnosperm (sidebar). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-545Wheat-Producing Countries, 1994 (bar graph) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1055Wheat Stem Rust: Five Stages (table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-931World Food Production (bar graph) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-40

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ALPHABETICAL LIST OF CONTENTS

Volume 1

Acid precipitation . . . . . . . . . . . . . . . . . . 1Active transport . . . . . . . . . . . . . . . . . . . 4Adaptations . . . . . . . . . . . . . . . . . . . . . 7Adaptive radiation. . . . . . . . . . . . . . . . . 10African agriculture. . . . . . . . . . . . . . . . . 12African flora . . . . . . . . . . . . . . . . . . . . 17Agricultural crops: experimental. . . . . . . . . 20Agricultural revolution . . . . . . . . . . . . . . 23Agriculture: history and overview. . . . . . . . 24Agriculture: marine . . . . . . . . . . . . . . . . 29Agriculture: modern problems . . . . . . . . . . 31Agriculture: traditional . . . . . . . . . . . . . . 34Agriculture: world food supplies . . . . . . . . 37Agronomy . . . . . . . . . . . . . . . . . . . . . 42Air pollution . . . . . . . . . . . . . . . . . . . . 43Algae . . . . . . . . . . . . . . . . . . . . . . . . 47Allelopathy . . . . . . . . . . . . . . . . . . . . . 51Alternative grains . . . . . . . . . . . . . . . . . 52Anaerobes and heterotrophs . . . . . . . . . . . 54Anaerobic photosynthesis . . . . . . . . . . . . 56Angiosperm cells and tissues. . . . . . . . . . . 58Angiosperm evolution . . . . . . . . . . . . . . 61Angiosperm life cycle . . . . . . . . . . . . . . . 65Angiosperm plant formation . . . . . . . . . . . 69Angiosperms . . . . . . . . . . . . . . . . . . . . 72Animal-plant interactions. . . . . . . . . . . . . 78Antarctic flora . . . . . . . . . . . . . . . . . . . 81Aquatic plants . . . . . . . . . . . . . . . . . . . 82Archaea . . . . . . . . . . . . . . . . . . . . . . . 84Arctic tundra . . . . . . . . . . . . . . . . . . . . 88Ascomycetes . . . . . . . . . . . . . . . . . . . . 90Asian agriculture. . . . . . . . . . . . . . . . . . 92Asian flora . . . . . . . . . . . . . . . . . . . . . 96ATP and other energetic molecules. . . . . . . 100Australian agriculture . . . . . . . . . . . . . . 103Australian flora . . . . . . . . . . . . . . . . . . 105Autoradiography . . . . . . . . . . . . . . . . . 109

Bacteria . . . . . . . . . . . . . . . . . . . . . . 112Bacterial genetics . . . . . . . . . . . . . . . . . 119Bacterial resistance and super bacteria . . . . . 121Bacteriophages . . . . . . . . . . . . . . . . . . 125Basidiomycetes . . . . . . . . . . . . . . . . . . . 127Basidiosporic fungi . . . . . . . . . . . . . . . . 129Biochemical coevolution in

angiosperms. . . . . . . . . . . . . . . . . . 131Biofertilizers. . . . . . . . . . . . . . . . . . . . 134Biological invasions . . . . . . . . . . . . . . . 136Biological weapons . . . . . . . . . . . . . . . . 139Bioluminescence . . . . . . . . . . . . . . . . . 142Biomass related to energy . . . . . . . . . . . . 144Biomes: definitions and determinants . . . . . 147Biomes: types . . . . . . . . . . . . . . . . . . . 150Biopesticides . . . . . . . . . . . . . . . . . . . 154Biosphere concept . . . . . . . . . . . . . . . . 157Biotechnology. . . . . . . . . . . . . . . . . . . 158Botany . . . . . . . . . . . . . . . . . . . . . . . 161Bromeliaceae . . . . . . . . . . . . . . . . . . . . 162Brown algae . . . . . . . . . . . . . . . . . . . . 164Bryophytes . . . . . . . . . . . . . . . . . . . . 166Bulbs and rhizomes . . . . . . . . . . . . . . . 169

C4 and CAM photosynthesis . . . . . . . . . . 172Cacti and succulents . . . . . . . . . . . . . . . 175Calvin cycle . . . . . . . . . . . . . . . . . . . . 178Carbohydrates . . . . . . . . . . . . . . . . . . 180Carbon cycle . . . . . . . . . . . . . . . . . . . 183Carbon 13/carbon 12 ratios . . . . . . . . . . . 186Caribbean agriculture . . . . . . . . . . . . . . 188Caribbean flora . . . . . . . . . . . . . . . . . . 190Carnivorous plants . . . . . . . . . . . . . . . . 192Cell cycle . . . . . . . . . . . . . . . . . . . . . 195Cell theory. . . . . . . . . . . . . . . . . . . . . 197Cell-to-cell communication . . . . . . . . . . . 199Cell wall . . . . . . . . . . . . . . . . . . . . . . 201

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Cells and diffusion . . . . . . . . . . . . . . . . 203Cellular slime molds . . . . . . . . . . . . . . . 205Central American agriculture . . . . . . . . . . 207Central American flora. . . . . . . . . . . . . . 210Charophyceae . . . . . . . . . . . . . . . . . . . . 211Chemotaxis . . . . . . . . . . . . . . . . . . . . 213Chlorophyceae . . . . . . . . . . . . . . . . . . . 216Chloroplast DNA. . . . . . . . . . . . . . . . . 218Chloroplasts and other plastids. . . . . . . . . 220Chromatin . . . . . . . . . . . . . . . . . . . . . 223Chromatography . . . . . . . . . . . . . . . . . 225Chromosomes. . . . . . . . . . . . . . . . . . . 228Chrysophytes . . . . . . . . . . . . . . . . . . . 230Chytrids . . . . . . . . . . . . . . . . . . . . . . 233Circadian rhythms . . . . . . . . . . . . . . . . 236Cladistics . . . . . . . . . . . . . . . . . . . . . 238Climate and resources . . . . . . . . . . . . . . 241Clines . . . . . . . . . . . . . . . . . . . . . . . 243Cloning of plants . . . . . . . . . . . . . . . . . 245Coal . . . . . . . . . . . . . . . . . . . . . . . . 247Coevolution . . . . . . . . . . . . . . . . . . . . 252Community-ecosystem interactions . . . . . . 255Community structure and stability. . . . . . . 257Competition . . . . . . . . . . . . . . . . . . . . 260

Complementation and allelism:the cis-trans test . . . . . . . . . . . . . . . . 263

Compositae . . . . . . . . . . . . . . . . . . . . . 265Composting . . . . . . . . . . . . . . . . . . . . 267Conifers . . . . . . . . . . . . . . . . . . . . . . 270Corn . . . . . . . . . . . . . . . . . . . . . . . . 273Cryptomonads . . . . . . . . . . . . . . . . . . 276Culturally significant plants. . . . . . . . . . . 278Cycads and palms . . . . . . . . . . . . . . . . 281Cytoplasm. . . . . . . . . . . . . . . . . . . . . 285Cytoskeleton . . . . . . . . . . . . . . . . . . . 289Cytosol. . . . . . . . . . . . . . . . . . . . . . . 291

Deforestation . . . . . . . . . . . . . . . . . . . 293Dendrochronology . . . . . . . . . . . . . . . . 297Desertification . . . . . . . . . . . . . . . . . . 300Deserts . . . . . . . . . . . . . . . . . . . . . . . 303Deuteromycetes. . . . . . . . . . . . . . . . . . 306Diatoms . . . . . . . . . . . . . . . . . . . . . . 307Dinoflagellates . . . . . . . . . . . . . . . . . . 311Diseases and disorders. . . . . . . . . . . . . . 313DNA: historical overview . . . . . . . . . . . . 316DNA in plants. . . . . . . . . . . . . . . . . . . 322DNA: recombinant technology . . . . . . . . . 326

Volume 2

DNA replication . . . . . . . . . . . . . . . . . 329Dormancy . . . . . . . . . . . . . . . . . . . . . 331Drought . . . . . . . . . . . . . . . . . . . . . . 334

Ecology: concept . . . . . . . . . . . . . . . . . 337Ecology: history. . . . . . . . . . . . . . . . . . 339Ecosystems: overview . . . . . . . . . . . . . . 341Ecosystems: studies . . . . . . . . . . . . . . . 344Electrophoresis . . . . . . . . . . . . . . . . . . 348Endangered species . . . . . . . . . . . . . . . 350Endocytosis and exocytosis . . . . . . . . . . . 355Endomembrane system and

Golgi complex . . . . . . . . . . . . . . . . . 358Endophytes . . . . . . . . . . . . . . . . . . . . 361Endoplasmic reticulum . . . . . . . . . . . . . 363Energy flow in plant cells . . . . . . . . . . . . 364Environmental biotechnology. . . . . . . . . . 367Erosion and erosion control . . . . . . . . . . . 369

Estrogens from plants . . . . . . . . . . . . . . 371Ethanol. . . . . . . . . . . . . . . . . . . . . . . 374Eudicots . . . . . . . . . . . . . . . . . . . . . . 375Euglenoids . . . . . . . . . . . . . . . . . . . . 378Eukarya. . . . . . . . . . . . . . . . . . . . . . . 380Eukaryotic cells . . . . . . . . . . . . . . . . . . 382European agriculture. . . . . . . . . . . . . . . 385European flora . . . . . . . . . . . . . . . . . . 389Eutrophication . . . . . . . . . . . . . . . . . . 393Evolution: convergent and

divergent . . . . . . . . . . . . . . . . . . . . 396Evolution: gradualism vs.

punctuated equilibrium . . . . . . . . . . . 398Evolution: historical perspective . . . . . . . . 400Evolution of cells . . . . . . . . . . . . . . . . . 404Evolution of plants . . . . . . . . . . . . . . . . 409Exergonic and endergonic reactions . . . . . . 412Extranuclear inheritance. . . . . . . . . . . . . 414

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Farmland . . . . . . . . . . . . . . . . . . . . . 417Ferns . . . . . . . . . . . . . . . . . . . . . . . . 419Fertilizers . . . . . . . . . . . . . . . . . . . . . 423Flagella and cilia . . . . . . . . . . . . . . . . . 426Flower structure . . . . . . . . . . . . . . . . . 428Flower types . . . . . . . . . . . . . . . . . . . 432Flowering regulation . . . . . . . . . . . . . . . 435Fluorescent staining of cytoskeletal

elements . . . . . . . . . . . . . . . . . . . . 438Food chain. . . . . . . . . . . . . . . . . . . . . 440Forest and range policy . . . . . . . . . . . . . 443Forest fires. . . . . . . . . . . . . . . . . . . . . 447Forest management . . . . . . . . . . . . . . . 450Forests . . . . . . . . . . . . . . . . . . . . . . . 454Fossil plants . . . . . . . . . . . . . . . . . . . . 458Fruit crops . . . . . . . . . . . . . . . . . . . . . 461Fruit: structure and types . . . . . . . . . . . . 464Fungi . . . . . . . . . . . . . . . . . . . . . . . . 469

Garden plants: flowering . . . . . . . . . . . . 474Garden plants: shrubs . . . . . . . . . . . . . . 478Gas exchange in plants. . . . . . . . . . . . . . 481Gene flow . . . . . . . . . . . . . . . . . . . . . 483Gene regulation. . . . . . . . . . . . . . . . . . 486Genetic code. . . . . . . . . . . . . . . . . . . . 488Genetic drift . . . . . . . . . . . . . . . . . . . . 490Genetic equilibrium: linkage . . . . . . . . . . 491Genetically modified bacteria . . . . . . . . . . 494Genetically modified foods . . . . . . . . . . . 496Genetics: Mendelian . . . . . . . . . . . . . . . 499Genetics: mutations . . . . . . . . . . . . . . . 503Genetics: post-Mendelian . . . . . . . . . . . . 505Germination and seedling development. . . . 509Ginkgos . . . . . . . . . . . . . . . . . . . . . . 512Glycolysis and fermentation . . . . . . . . . . 515Gnetophytes. . . . . . . . . . . . . . . . . . . . 517Grains . . . . . . . . . . . . . . . . . . . . . . . 520Grasses and bamboos . . . . . . . . . . . . . . 522Grasslands. . . . . . . . . . . . . . . . . . . . . 525Grazing and overgrazing . . . . . . . . . . . . 527Green algae . . . . . . . . . . . . . . . . . . . . 530Green Revolution . . . . . . . . . . . . . . . . . 532Greenhouse effect. . . . . . . . . . . . . . . . . 534Growth and growth control . . . . . . . . . . . 537Growth habits. . . . . . . . . . . . . . . . . . . 541Gymnosperms . . . . . . . . . . . . . . . . . . 544

Halophytes . . . . . . . . . . . . . . . . . . . . 548Haptophytes . . . . . . . . . . . . . . . . . . . 551Hardy-Weinberg theorem . . . . . . . . . . . . 554Heliotropism . . . . . . . . . . . . . . . . . . . 557Herbicides . . . . . . . . . . . . . . . . . . . . . 558Herbs. . . . . . . . . . . . . . . . . . . . . . . . 561Heterokonts . . . . . . . . . . . . . . . . . . . . 564High-yield crops . . . . . . . . . . . . . . . . . 566History of plant science . . . . . . . . . . . . . 569Hormones . . . . . . . . . . . . . . . . . . . . . 575Hornworts. . . . . . . . . . . . . . . . . . . . . 578Horsetails . . . . . . . . . . . . . . . . . . . . . 581Horticulture . . . . . . . . . . . . . . . . . . . . 583Human population growth . . . . . . . . . . . 586Hybrid zones . . . . . . . . . . . . . . . . . . . 589Hybridization . . . . . . . . . . . . . . . . . . . 591Hydrologic cycle . . . . . . . . . . . . . . . . . 593Hydroponics . . . . . . . . . . . . . . . . . . . 597

Inflorescences . . . . . . . . . . . . . . . . . . . 600Integrated pest management . . . . . . . . . . 602Invasive plants . . . . . . . . . . . . . . . . . . 604Irrigation . . . . . . . . . . . . . . . . . . . . . 607

Krebs cycle . . . . . . . . . . . . . . . . . . . . 610

Leaf abscission . . . . . . . . . . . . . . . . . . 613Leaf anatomy . . . . . . . . . . . . . . . . . . . 616Leaf arrangements . . . . . . . . . . . . . . . . 619Leaf lobing and division . . . . . . . . . . . . . 621Leaf margins, tips, and bases . . . . . . . . . . 624Leaf shapes . . . . . . . . . . . . . . . . . . . . 627Legumes . . . . . . . . . . . . . . . . . . . . . . 629Lichens. . . . . . . . . . . . . . . . . . . . . . . 632Lipids . . . . . . . . . . . . . . . . . . . . . . . 634Liquid transport systems . . . . . . . . . . . . 636Liverworts. . . . . . . . . . . . . . . . . . . . . 640Logging and clear-cutting . . . . . . . . . . . . 643Lycophytes . . . . . . . . . . . . . . . . . . . . 645

Marine plants . . . . . . . . . . . . . . . . . . . 649Medicinal plants . . . . . . . . . . . . . . . . . 652Mediterranean scrub . . . . . . . . . . . . . . . 655Membrane structure . . . . . . . . . . . . . . . 658Metabolites: primary vs.

secondary . . . . . . . . . . . . . . . . . . . 659

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Alphabetical List of Contents

Volume 3

Microbial nutrition and metabolism . . . . . . 663Microbodies . . . . . . . . . . . . . . . . . . . . 666Microscopy . . . . . . . . . . . . . . . . . . . . 668Mitochondria . . . . . . . . . . . . . . . . . . . 672Mitochondrial DNA . . . . . . . . . . . . . . . 675Mitosis and meiosis . . . . . . . . . . . . . . . 677Mitosporic fungi . . . . . . . . . . . . . . . . . 681Model organisms . . . . . . . . . . . . . . . . . 682Molecular systematics . . . . . . . . . . . . . . 686Monocots vs. dicots . . . . . . . . . . . . . . . 688Monocotyledones . . . . . . . . . . . . . . . . . . 690Monoculture . . . . . . . . . . . . . . . . . . . 692Mosses . . . . . . . . . . . . . . . . . . . . . . . 694Multiple-use approach . . . . . . . . . . . . . . 697Mushrooms . . . . . . . . . . . . . . . . . . . . 699Mycorrhizae. . . . . . . . . . . . . . . . . . . . 702

Nastic movements . . . . . . . . . . . . . . . . 704Nitrogen cycle . . . . . . . . . . . . . . . . . . 706Nitrogen fixation . . . . . . . . . . . . . . . . . 709Nonrandom mating . . . . . . . . . . . . . . . 712North American agriculture. . . . . . . . . . . 714North American flora . . . . . . . . . . . . . . 718Nuclear envelope . . . . . . . . . . . . . . . . . 722Nucleic acids . . . . . . . . . . . . . . . . . . . 723Nucleolus . . . . . . . . . . . . . . . . . . . . . 727Nucleoplasm . . . . . . . . . . . . . . . . . . . 729Nucleus . . . . . . . . . . . . . . . . . . . . . . 730Nutrient cycling . . . . . . . . . . . . . . . . . 732Nutrients . . . . . . . . . . . . . . . . . . . . . 734Nutrition in agriculture . . . . . . . . . . . . . 737

Oil bodies . . . . . . . . . . . . . . . . . . . . . 740Old-growth forests . . . . . . . . . . . . . . . . 741Oomycetes. . . . . . . . . . . . . . . . . . . . . 743Orchids . . . . . . . . . . . . . . . . . . . . . . 745Organic gardening and farming . . . . . . . . 747Osmosis, simple diffusion, and

facilitated diffusion . . . . . . . . . . . . . . 751Oxidative phosphorylation . . . . . . . . . . . 755Ozone layer and ozone hole debate . . . . . . 757

Pacific Island agriculture . . . . . . . . . . . . 761Pacific Island flora . . . . . . . . . . . . . . . . 765

Paclitaxel . . . . . . . . . . . . . . . . . . . . . 768Paleobotany . . . . . . . . . . . . . . . . . . . . 770Paleoecology . . . . . . . . . . . . . . . . . . . 774Parasitic plants . . . . . . . . . . . . . . . . . . 777Peat. . . . . . . . . . . . . . . . . . . . . . . . . 779Peroxisomes . . . . . . . . . . . . . . . . . . . . 782Pesticides . . . . . . . . . . . . . . . . . . . . . 783Petrified wood . . . . . . . . . . . . . . . . . . 787Pheromones . . . . . . . . . . . . . . . . . . . . 790Phosphorus cycle . . . . . . . . . . . . . . . . . 791Photoperiodism. . . . . . . . . . . . . . . . . . 794Photorespiration . . . . . . . . . . . . . . . . . 796Photosynthesis . . . . . . . . . . . . . . . . . . 800Photosynthetic light absorption. . . . . . . . . 804Photosynthetic light reactions. . . . . . . . . . 807Phytoplankton . . . . . . . . . . . . . . . . . . 809Pigments in plants . . . . . . . . . . . . . . . . 812Plant biotechnology . . . . . . . . . . . . . . . 815Plant cells: molecular level . . . . . . . . . . . 821Plant domestication and breeding . . . . . . . 826Plant fibers . . . . . . . . . . . . . . . . . . . . 829Plant life spans . . . . . . . . . . . . . . . . . . 831Plant science. . . . . . . . . . . . . . . . . . . . 835Plant tissues . . . . . . . . . . . . . . . . . . . . 839Plantae . . . . . . . . . . . . . . . . . . . . . . . 843Plants with potential . . . . . . . . . . . . . . . 849Plasma membranes. . . . . . . . . . . . . . . . 851Plasmodial slime molds . . . . . . . . . . . . . 854Poisonous and noxious plants . . . . . . . . . 857Pollination. . . . . . . . . . . . . . . . . . . . . 862Polyploidy and aneuploidy . . . . . . . . . . . 865Population genetics . . . . . . . . . . . . . . . 868Prokaryotes . . . . . . . . . . . . . . . . . . . . 870Proteins and amino acids . . . . . . . . . . . . 873Protista . . . . . . . . . . . . . . . . . . . . . . . 875Psilotophytes . . . . . . . . . . . . . . . . . . . 879

Rain-forest biomes . . . . . . . . . . . . . . . . 883Rain forests and the atmosphere . . . . . . . . 885Rangeland . . . . . . . . . . . . . . . . . . . . . 889Red algae . . . . . . . . . . . . . . . . . . . . . 892Reforestation . . . . . . . . . . . . . . . . . . . 894Reproduction in plants. . . . . . . . . . . . . . 897Reproductive isolating mechanisms . . . . . . 899

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Resistance to plant diseases . . . . . . . . . . . 901Respiration . . . . . . . . . . . . . . . . . . . . 904Rhyniophyta . . . . . . . . . . . . . . . . . . . . 907Ribosomes . . . . . . . . . . . . . . . . . . . . . 909Rice. . . . . . . . . . . . . . . . . . . . . . . . . 912RNA . . . . . . . . . . . . . . . . . . . . . . . . 914Root uptake systems . . . . . . . . . . . . . . . 917Roots . . . . . . . . . . . . . . . . . . . . . . . . 920Rubber . . . . . . . . . . . . . . . . . . . . . . . 925Rusts . . . . . . . . . . . . . . . . . . . . . . . . 929

Savannas and deciduous tropical forests . . . 932Seedless vascular plants . . . . . . . . . . . . . 934Seeds . . . . . . . . . . . . . . . . . . . . . . . . 937Selection . . . . . . . . . . . . . . . . . . . . . . 941Serpentine endemism . . . . . . . . . . . . . . 943Shoots . . . . . . . . . . . . . . . . . . . . . . . 944Slash-and-burn agriculture . . . . . . . . . . . 946

Soil . . . . . . . . . . . . . . . . . . . . . . . . . 949Soil conservation . . . . . . . . . . . . . . . . . 955Soil contamination . . . . . . . . . . . . . . . . 957Soil degradation . . . . . . . . . . . . . . . . . 959Soil management . . . . . . . . . . . . . . . . . 962Soil salinization . . . . . . . . . . . . . . . . . . 963South American agriculture . . . . . . . . . . . 965South American flora . . . . . . . . . . . . . . 969Species and speciation . . . . . . . . . . . . . . 973Spermatophyta . . . . . . . . . . . . . . . . . . . 976Spices . . . . . . . . . . . . . . . . . . . . . . . 977Stems. . . . . . . . . . . . . . . . . . . . . . . . 980Strip farming . . . . . . . . . . . . . . . . . . . 983Stromatolites . . . . . . . . . . . . . . . . . . . 985Succession . . . . . . . . . . . . . . . . . . . . . 988Sugars . . . . . . . . . . . . . . . . . . . . . . . 991Sustainable agriculture. . . . . . . . . . . . . . 993

Volume 4

Sustainable forestry . . . . . . . . . . . . . . . 997Systematics and taxonomy . . . . . . . . . . . 999Systematics: overview . . . . . . . . . . . . . 1004

Taiga . . . . . . . . . . . . . . . . . . . . . . . 1007Textiles and fabrics . . . . . . . . . . . . . . . 1009Thigmomorphogenesis . . . . . . . . . . . . . 1013Timber industry . . . . . . . . . . . . . . . . . 1015Tracheobionta . . . . . . . . . . . . . . . . . . . 1017Trimerophytophyta . . . . . . . . . . . . . . . . 1021Trophic levels and ecological niches . . . . . 1023Tropisms . . . . . . . . . . . . . . . . . . . . . 1027Tundra and high-altitude biomes . . . . . . . 1030

Ulvophyceae. . . . . . . . . . . . . . . . . . . . 1033Ustomycetes. . . . . . . . . . . . . . . . . . . . 1035

Vacuoles . . . . . . . . . . . . . . . . . . . . . 1037Vegetable crops . . . . . . . . . . . . . . . . . 1039Vesicle-mediated transport. . . . . . . . . . . 1043Viruses and viroids . . . . . . . . . . . . . . . 1045

Water and solute movement in plants . . . . 1048Wetlands . . . . . . . . . . . . . . . . . . . . . 1051

Wheat. . . . . . . . . . . . . . . . . . . . . . . 1054Wood . . . . . . . . . . . . . . . . . . . . . . . 1056Wood and charcoal as fuel resources . . . . . 1058Wood and timber . . . . . . . . . . . . . . . . 1060

Yeasts . . . . . . . . . . . . . . . . . . . . . . . 1065

Zosterophyllophyta . . . . . . . . . . . . . . . . 1067Zygomycetes. . . . . . . . . . . . . . . . . . . 1069

Biographical List of Botanists . . . . . . . . . 1073Plant Classification . . . . . . . . . . . . . . . 1105Plant Names: Common-to-

Scientific . . . . . . . . . . . . . . . . . . . . 1115Plant Names: Scientific-to-

Common . . . . . . . . . . . . . . . . . . . 1130Time Line. . . . . . . . . . . . . . . . . . . . . 1199Glossary . . . . . . . . . . . . . . . . . . . . . 1207Bibliography . . . . . . . . . . . . . . . . . . . 1244Web Sites . . . . . . . . . . . . . . . . . . . . . 1254

Biographical Index. . . . . . . . . . . . . . . . . IIICategorized Index . . . . . . . . . . . . . . . . VIIIndex . . . . . . . . . . . . . . . . . . . . . . . XVII

xxi

Alphabetical List of Contents

MICROBIAL NUTRITION AND METABOLISM

Categories: Algae; bacteria; fungi; microorganisms; nutrients and nutrition; Protista

The diverse metabolic activities of microorganisms make them a critical component of all the earth’s ecosystems and asource of many useful products for human industry.

Microorganisms—bacteria, fungi, algae, andprotists—are found in every environment onthe earth that supports life. Microorganisms havebeen found in hot springs where temperatures ex-ceed 80 degrees Celsius as well as in rocks of Ant-arctic deserts. To ensure survival in a variety of hab-itats, microorganisms have developed a fascinatingvariety of strategies for survival. The study of mi-crobial ecology involves consideration of the mech-anisms employed by microorganisms to obtain nu-trients and energy from their environment.

Nutritional ModesTo maintain life processes and grow, all cellular

organisms require both a source of carbon (the prin-cipal element in all organic molecules) and a sourceof energy to perform the work necessary to trans-form carbon into all the molecular components ofcytoplasm. Among plants and animals, two mainnutritional modes have evolved to meet these re-quirements. All plants are photoautotrophs, fixingcarbon from inorganic carbon and obtaining energyfrom light. All animals are chemoheterotrophs, meet-ing their carbon needs by taking preformed organicmolecules from the environment and extracting en-ergy from chemical transformation of the same or-ganic molecules.

Both of these nutritional modes, photoauto-trophy and chemoheterotrophy, are found amongmicroorganisms; for example, all algae are photo-autotrophs, while all fungi are chemoheterotrophs.In addition, certain specialized bacteria exhibit amode of nutrition, chemoautotrophy, found in nohigher organisms. Like photoautotrophs, chemo-autotrophs are able to use carbon dioxide for allof their carbon requirements; however, they donot use light as an energy source. Instead, chemo-autotrophic bacteria capture energy from inorganic

chemical reactions, such as the oxidation of ammo-nia. Chemoautotrophic bacteria are highly special-ized and can be found in unusual environments.The most spectacular display of chemoautotrophicenergy metabolism is exhibited at the hydrother-mal vents found in certain locations on the oceanfloor. There, where sunlight cannot penetrate, che-moautotrophic bacteria serve as the producers for arich and diverse ecosystem.

An appreciation of the metabolic diversity dis-played by microorganisms enhances understand-ing of the ways in which matter and energy aretransformed in the biosphere. Consideration of mi-crobial contributions to the flow of carbon, nitro-gen, and other elements is critical to defining thebalance of ecosystems and the effects of changes inenvironmental chemistry and species composition.Microorganisms are, by definition, unseen, andmany people become aware of them only in theirnegative manifestations as agents of disease andspoilage. In fact, however, the diverse metabolic ac-tivities of microorganisms make them a criticalcomponent of all the earth’s ecosystems and a sourceof many useful products for human industry.

Cellulose DigestionEven among chemoheterotrophs, microorgan-

isms possess metabolic capabilities unknown inhigher organisms. These include the ability of somebacteria and fungi to digest cellulose, a linear poly-mer of glucose that is the principal molecular con-stituent of paper. Sixty percent of the dry mass ofgreen plants is in the form of cellulose, although noanimal that eats the plants is directly able to obtaincarbon or energy from cellulose. Microorganismsthat digest cellulose do so by secreting exoenzymes,proteins that cause cellulose to be broken into sim-pler molecular units that are absorbed by the micro-

Microbial nutrition and metabolism • 663

organism. Cellulose-digesting microorganisms arefound in most terrestrial ecosystems and in the di-gestive tracts of animals, such as cattle and ter-mites, that depend on cellulose-rich plant materialas a nutrient source. By breaking down celluloseand other complex organic polymers, microorgan-isms make a significant contribution to the cyclingof carbon in ecosystems.

Nitrogen FixationDigestion of complex organic polymers is only

one of the ways in which microorganisms contrib-ute to the cycling of elements in the environmentsthey inhabit. Microorganisms also perform chemi-cal transformations involving nitrogen, which isfound in all cellular proteins and nucleic acids.Plants incorporate nitrogen from the soil in theform of nitrate or ammonium ions, and animals ob-tain nitrogen from the same organic compoundsthey use as carbon and energy sources.

When dead plant and animal tissue is decom-posed by chemoheterotrophic microorganisms, thenitrogen is released as ammonia. A group ofchemoautotrophic bacteria, the nitrifying bacteria,obtain their metabolic energy from the conversionof ammonia to nitrate; in this way, the nitrifiers con-vert the nitrogen released during decomposition toa form readily used by plants, thus contributing tosoil fertility. Asecond group of bacteria converts ni-trate to atmospheric nitrogen gas, which cannot beused by plants; these bacteria are called denitrifiersbecause (in contrast to the nitrifiers) their metabolicactivities cause a net loss of nitrogen from the soil.

Nitrogen lost from the environment by deni-trification is replaced by ammonia released duringdecomposition and by the metabolic activity ofnitrogen-fixing bacteria, so called because they “fix”nitrogen gas from the atmosphere in the form ofammonia. Nitrogen fixation requires a great quan-tity of energy, and nitrogen-fixing bacteria are often

664 • Microbial nutrition and metabolism

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found in symbiotic association with plants, espe-cially legumes. The bacteria provide nitrogen in ausable form to the plant, while the plant providescarbon and energy in the form of organic com-pounds to the chemoheterotrophic nitrogen-fixingbacteria. The presence of nitrogen-fixing bacteria isoften indicated by the formation of characteristicnodules on the roots of plants involved in the asso-ciations. Free-living nitrogen fixers are also known,and these may play a significant role in the nitrogenbalance of aquatic ecosystems.

Respiration and FermentationChemoheterotrophic microorganisms are found

both in aerobic environments, where oxygen is avail-able, and in anaerobic environments, where oxygenis lacking. The availability of molecular oxygenmay determine the type of energy metabolismemployed by a microorganism. Where oxygen isavailable, many microorganisms obtain energy byrespiration. In respiration, electrons removed fromorganic nutrient sources are transferred through acomplex sequence of reactions to molecular oxy-gen, forming water and carbon dioxide. In the pro-cess, energy is made available to the organisms. Inthe absence of oxygen, some microorganisms areable to carry out a form of anaerobic respiration us-ing nitrate or sulfate in place of oxygen. Deni-trification is an example of anaerobic respiration.

Other anaerobic microorganisms employ fer-mentation. In fermentation, electrons removed fromorganic nutrient sources are transferred to organicmolecules, forming fermentation products, such asalcohols and organic acids, which may be used asnutrient sources by other chemoheterotrophs. Anumber of bacteria, the facultative anaerobes, are ca-pable of performing either aerobic respiration orfermentation, depending on the availability of oxy-gen. These bacteria are able to achieve optimumgrowth in environments, such as soils, where theavailability of oxygen may vary over time.

Effects and UsesThe contributions of microorganisms to the

chemical transformations which characterize anecosystem are many. Along with higher plants,photoautotrophic and chemoautotrophic microor-ganisms capture inorganic carbon dioxide and, us-ing energy from sunlight or chemical reactions,synthesize organic molecules, which are used byanimals and by chemoheterotrophic microorgan-

isms as sources of carbon and energy. Through theprocesses of respiration and fermentation, chemo-heterotrophs return inorganic carbon dioxide to theenvironment.

Much of this recycling of carbon from organicmolecules to carbon dioxide depends on the activi-ties of microbial decomposers, which are able tobreak down organic polymers, such as cellulose.Nitrogen, released from organic molecules bychemoheterotrophs in the form of ammonia, maybe made available to chemohe

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