Plant Anatomy Richard Crang† Sheila Lyons-Sobaski Robert Wise Plant Anatomy

A Concept-Based Approach to the Structure of Seed Plants Richard Crang† Sheila Lyons-Sobaski Department of Plant Biology Biology Department University of Illinois at Urbana-Champaign Albion College Urbana, IL Albion, MI USA USA

Robert Wise Biology Department University of Wisconsin, Oshkosh Oshkosh, WI USA

†Deceased

ISBN 978-3-319-77208-0 ISBN 978-3-319-77315-5 (eBook) https://doi.org/10.1007/978-3-319-77315-5

Library of Congress Control Number: 2018948823

© Springer Nature Switzerland AG 2018, corrected publication 2019 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recita- tion, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Cover illustration: SEM of Alium sp. leaf cross section and LM of Clematis sp. stem cross-section.

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Richard was a vital contributor to this project from its infancy to its final production phase. We take some comfort that he knew the book was essentially complete prior to his passing. We greatly miss our colleague and friend, and so we dedicate this book to Richard who was a courageous and venturesome guy, a brilliant scholar, an innovative teacher, and a kind, thoughtful man.

SLS and RRW Preface

The science of plant anatomy extends back made a substantial effort to update the to the late seventeenth century and, by subject matter, reveal new ways in which now, spans over 300 years and encom- aspects of plant anatomy play a key role in passes hundreds of thousands of reports in a variety of related disciplines in plant the scientific literature. The early plant biology, and present the topics in an anatomy research was summarized in understandable and interesting manner to 1899 by Dr. Hans Solereder in his two vol- the student and instructor. Heavy reliance ume work entitled Systematische Anatomie was made on original light and electron der Dicotyledonen: Ein Handbuch für Lab- micrographs, and color has been used oratorien der wissenschaftlichen und ange- extensively. Literature citations were kept wandten Botanik. The 1908 English to a minimum because, in today’s elec- translation by Boodle, Fritsch, and Scott tronically searchable world, a wealth of remains as fresh, informative, and useful knowledge on any topic is a mere click or today as when it was published over two away. 100 years ago. Several important texts were published in the 1950s. The two-volume This effort was started over two decades work of Metcalfe and Chalk, Anatomy of ago when a collaboration between Prof. the Dicotyledons (1950) with second edi- Richard Crang of the University of Illinois tions in 1979 (Volume 1) and 1983 (Vol- at Urbana-Champaign and Prof. Andrey ume 2), is a thorough survey of anatomical Vassilyev of the Komarov Botanical Insti- traits and features arranged by family. tute in St. Petersburg, Russia, identified the Some of the taxonomy has been rear- need for novel approaches to the teaching ranged, but the anatomical references of plant anatomy. This led to the develop- remain accurate and valuable. The year ment that used modern educational tech- 1953 saw the publication of the first edi- nologies in a searchable, compact disk tion of the classic Plant Anatomy by Kath- format that presented a traditional view erine Esau. Encyclopedic in its coverage, regarding the anatomy of temperate seed insightful in interpretation, and complete plants, their place in evolution, and taxo- in its synthesis, “Esau” (as it has been nomic relations, with a novel approach in referred to by several generations of bota- subject delivery. Although Prof. Vassilyev nists) remains a go-to reference to this day. died in 2012, his significant contributions A second edition was released in 1977 and to botany must not be overlooked. Edu- Dr. Ray Evert authored the third, revised cated in dendrology, he devoted his life to edition, published in 2006. Additionally, plant anatomy, specializing in plant secre- the 1988 Plant Anatomy by Dr. James tory structures. Dr. Vassilyev worked at the Mauseth and Dr. Avraham Fahn’s 1967 Komarov Botanical Institute and Garden Plant Anatomy (4th edition in 1990) in St. Petersburg (formerly Leningrad), belong on every plant anatomist’s book Russia, and rose to the position of Lead shelf as valuable references. Scientist at that institute. His contributions in the field of plant anatomy, and to the In 2018, plant anatomy continues to play beginnings of this project, must be noted. key roles in studies of molecular plant biology, forestry, plant pathology, plant It has been felt for some time that a new physiology, horticulture, agronomy, and a and more extensive approach to the teach- host of related botanical disciplines. There- ing of plant anatomy should be developed. fore, the authors of this plant anatomy Such plans began in 2013 and grew to resource – printed book and e-book – have include two established plant biologists VII Preface with extensive backgrounds in plant anat- ground in microscopy applications as well omy. Prof. Robert Wise of the University of as years of experience in teaching courses Wisconsin at Oshkosh and Dr. Sheila and research in plant anatomy to this Lyons-Sobaski from Albion College in effort. Michigan each bring new ideas and experiences to this effort in publishing. May the concepts of plant structure and Prof. Wise integrates anatomy and elec- development help open our minds to a tron microscopy with a full background in better understanding of the interrelation- plant physiology, and Dr. Lyons-Sobaski ship of life in its various forms throughout has added strength in ecology and evolu- the Earth and, perhaps, beyond. And may tion with relevance to plant anatomy. Prof. this text help, in a limited way, to aid in Emeritus Crang conveyed a lengthy back- that fuller understanding.

Richard Crang† Urbana, IL, USA

Sheila Lyons-Sobaski Albion, MI, USA

Robert Wise Oshkosh, WI, USA

†Deceased

The original version of this book was revised. The correction to this book can be found at https://doi.org/10.1007/978-3-319-77315-5_20 Acknowledgments

Support from the following persons has Dr. Brett Jestrow, Fairchild Tropical been invaluable to the success of this Botanic Garden, Miami project. With their help, the authors gained access to literally thousands of prepared Mr. Tom Perzentka, University of Wiscon- slides and specimens and were able to con- sin, Oshkosh, WI struct a library of over 10,000 images that formed the basis of this book project. Their Dr. Brian Piasecki, Lawrence University, assistance is greatly appreciated. We par- Appleton, WI ticularly wish to acknowledge and thank Dr. George Rogers, Palm Beach State Col- Eric Stannard, Senior Botany Editor, lege, Palm Beach Gardens, FL Springer for all his help and support in this project. Ms. JoAnn Stamm, Lawrence University, Appleton, WI Dr. Ranessa Cooper, Western Illinois Uni- versity, Macomb, Illinois Dr. Qiang Sun, University of Wisconsin, Stevens Point, WI Dr. John D. Curtis, University of Wiscon- sin, Stevens Point, WI This work was supported by grants from the Hewlett-Mellon Fund for Faculty Mr. John Hardy, University of Wisconsin, Development at Albion College, Albion, Stevens Point, WI MI and the University of Wisconsin Osh- kosh Faculty Development Program, Osh- Dr. James Horn, University of Wisconsin, kosh, WI. Green Bay, WI

Dr. Harry Horner, Iowa State University, Ames, Iowa IX

Contents

I Plants as Unique Organisms; History and Tools of Plant Anatomy

1 The Nature of Plants �� 3 1.1 Plants Have Multiple Pigments with Multiple Functions �� 5 1.2 Plants Use Water, and the Properties of Water, in Unique Ways �� 6 1.3 Plants Use Anabolic Metabolism to Manufacture Every Molecule Needed for Growth and Produce Virtually No Waste �� 8 1.4 Cell Walls Are Nonliving Matrices Outside the Plant Cell Membrane that House and/or Perform a Variety of Functions �� 9 1.5 The Plant Life Cycle Alternates Between a Haploid Gametophyte Stage and a Diploid Sporophyte Stage �� 10 1.6 Meristematic Activity Continues Throughout the Life of a Plant �� 11 1.7 Fruits Disperse Seeds Through Space: Dormancy Disperses Seeds Through Time �� 13 1.8 Earth’s History Is Divided into Four Major Time Periods �� 15 1.8.1 The Precambrian: 4550 to 542 mya �� 15 1.8.2 The Paleozoic Era: 542 to 251 mya �� 16 1.8.3 The Mesozoic Era: 251–66 mya �� 17 1.8.4 The Cenozoic Era: 66 mya to Present �� 17 1.9 Life on Earth Has Experienced Five Mass Extinctions: A Sixth Is in Progress �� 17 1.10 Many Plants and Animals Have Coevolved �� 18 1.11 The Plant Body Consists of Four Organs �� 19 1.11.1 Roots �� 19 1.11.2 Stems �� 20 1.11.3 Leaves �� 21 1.11.4 Flowers and Fruit�� 21 1.12 Plant Organs Are Initially Made of Three Tissues �� 24 1.13 “Plant” Can Be Broadly Defined �� 25 1.14 Bryophytes Lack Vasculature and Produce Spores �� 27 1.15 Ferns and Fern Allies Are Seedless Tracheophytes �� 28 1.16 Gymnosperms Are Seed-Producing Tracheophytes that Lack Flowers and Fruit �� 29 1.17 Monocots and Eudicots Are the Two Largest Groups of Angiosperms �� 31 1.18 Understanding Plant Structure Requires a Sense of Scale �� 33 1.19 “Primary” and “Secondary” Are Important Concepts in Plant Anatomy �� 34 1.19.1 Primary Versus Secondary Growth and Meristems �� 34 1.19.2 Primary Versus Secondary Xylem and Phloem �� 36 1.19.3 Primary Versus Secondary Cell Walls �� 37 1.20 Chapter Review �� 38 References and Additional Readings �� 44

2 Microscopy and Imaging �� 45 2.1 Robert Hooke, 1635–1703, Described a Cell as the Basic Unit of Life by Studying the Bark of the Cork Oak Tree, Quercus suber �� 47 2.2 Antoni Van Leeuwenhoek, 1632–1723, Was the First Scientist to Observe Microorganisms �� 48 2.3 Nehemiah Grew, 1641–1712, Was the Father of Plant Anatomy �� 50 2.4 Robert Brown, 1773–1858, Discovered the Nucleus of the Cell by Studying Orchid Petals �� 51 X Contents

2.5 Katherine Esau, 1898–1997, Advanced the Field of Plant Anatomy with Her Influential Textbooks �� 52 2.6 Light Microscopy: The Most Useful Tool of the Plant Anatomist �� 54 2.7 The Compound Light Microscope Uses Multiple Lenses to Form and Capture Images �� 55 2.8 The Resolving Power of a Lens Places Limits on Resolution and Magnification �� 56 2.9 The Confocal Microscope Allows for Sharper Detail, Computer Control, and 3-D Imaging with a Modified Compound Microscope �� 58 2.10 Electron Microscopy Allows a View into the World of Cellular Ultrastructure �� 61 2.11 The Transmission Electron Microscope Reveals Internal Cellular Detail �� 63 2.12 The Scanning Electron Microscope Resolves Surface Detail �� 66 2.13 Different Microscopies Produce Different Images of the Same Specimen �� 68 2.14 Chapter Review �� 69 References and Additional Readings �� 74

II Cellular Plant Anatomy

3 Plant Cell Structure and Ultrastructure �� 77 3.1 Plant Cells Are Complex Structures �� 79 3.2 Plant Cells Synthesize an External Wall and Contain a Variety of Internal Compartments �� 80 3.3 Cells and Cell Organelles Are Typically Bound by Lipid Bilayer Membranes �� 81 3.4 Vacuoles Play a Role in Water and Ion Balance �� 84 3.5 Plastids Are a Diverse Family of Anabolic Organelles �� 85 3.5.1 Proplastid �� 86 3.5.2 Etioplast �� 86 3.5.3 Elaioplast �� 87 3.5.4 Amyloplast �� 88 3.5.5 Chromoplast �� 90 3.5.6 Gerontoplast �� 90 3.5.7 Chloroplast �� 90 3.5.8 Chloroplast Functions �� 92

3.5.9 The Dimorphic Chloroplasts of C4 Photosynthesis �� 94 3.5.10 Guard Cell Chloroplasts �� 96 3.5.11 Sun Versus Shade Chloroplasts �� 96 3.6 All Plastids Are Developmentally Related �� 99 3.7 Mitochondria Synthesize ATP and Small Carbon Skeletons �� 100 3.8 Microbodies Are the Site of Specific Biochemical Pathways �� 100 3.9 The Endoplasmic Reticulum Synthesizes Proteins and Some Lipids �� 102 3.10 The Golgi Apparatus Processes and Packages Polysaccharides and Proteins for Secretion �� 105 3.11 The Nucleus Houses the Cell’s Genetic Material and Participates in Ribosome Synthesis �� 109 3.12 The Cytoskeleton Organizes the Cell and Helps Traffic Organelles �� 111 3.13 Chapter Review �� 116 References and Additional Readings �� 120

4 Mitosis and Meristems �� 123 4.1 The Plant Cell Cycle Includes Interphase, Mitosis, and Cytokinesis �� 125 4.2 A Pre-prophase Microtubule Band Precedes Mitosis and Defines the Plane of Cell Division �� 126 XI Contents

4.3 Mitosis May Be Divided into Distinct, but Continuous, Stages �� 127 4.4 Cytokinesis Begins with Initiation of the Cell Plate and Grows by the Deposition of Callose �� 130 4.5 Microtubules Play a Critical Role in Mitosis and Cytokinesis �� 132 4.6 Apical Meristems Are the Sites of Primary Growth �� 134 4.7 The Shoot Apical Meristem Is the Site of Lateral Organ Initiation �� 135 4.8 Axillary Buds Arise De Novo in the Developing Leaf Axis �� 136 4.9 Tunica-Corpus Organization Describes Shoot Apical Meristem Growth in Many Eudicots �� 139 4.10 Gymnosperms Do Not Possess a Tunica-Corpus �� 140 4.11 The Root Apical Meristem Provides the Primary Growth of Roots �� 140 4.12 Lateral Roots Originate from Inside the Pericycle, Not from the Root Apical Meristem �� 142 4.13 Intercalary Meristems Contribute to Stem and Leaf Growth in Monocots �� 144 4.14 Many Lower Vascular Plants Have a Single Initial Cell in the Shoot and Root Apical Meristems �� 145 4.15 Lateral Meristems Are the Site of Secondary Growth in Eudicots �� 146 4.16 Chapter Review �� 147 References and Additional Readings �� 153

5 Cell Walls �� 155 5.1 Transparent Plant Cell Walls Contain Cellulose and Are Synthesized to the Exterior of the Protoplast �� 156 5.2 Primary Cell Walls Are a Structural Matrix of Cellulose and Several Other Components �� 158 5.3 Plasmodesmata Connect Adjacent Cells Via Holes in the Primary Cell Wall �� 163 5.4 Secondary Cell Walls Are Rigid, Thick, and Lignified �� 167 5.5 Pits Are Holes in the Secondary Cell Wall �� 169 5.6 Transfer Cells Have Elaborated Primary Cell Walls for High Rates of Transport �� 173 5.7 Chapter Review �� 175 References and Additional Readings �� 178

6 Parenchyma, Collenchyma, and Sclerenchyma �� 181 6.1 Parenchyma Cells Are the Most Common Plant Cell Type �� 182 6.2 Parenchyma Cells May Exhibit Totipotency �� 188 6.3 Collenchyma Cells Are Used for Support and Are the Least Common Cell Type �� 189 6.4 Birefringence Is a Common Phenomenon in Collenchyma Walls �� 193 6.5 Sclerenchyma Cells Provide Support, Protection, and Long-Distance Water Transport �� 195 6.6 Fibers Impart Support and Protection �� 196 6.7 Sclereids Are Reduced Sclerenchyma Cells That Occur Singly or in Clumps �� 200 6.8 Xylem Vessel Elements Are Water-Conducting Sclerenchyma �� 206 6.9 Chapter Review �� 208 References and Additional Readings �� 212

III Vascular Tissues

7 Xylem �� 217 7.1 Xylem Is a Complex Tissue Containing Multiple Cell Types, Each with a Specific Structure and Function �� 218 XII Contents

7.2 The Primary Functions of Xylem Are Water Conduction, Mineral Transport, and Support �� 220 7.3 Tracheids Are Imperforate Tracheary Elements and the Sole Water Conductors in Gymnosperms �� 223 7.4 Angiosperm Tracheids, Fiber Tracheids, and Libriform Fibers Represent a Continuum of Imperforate Tracheary Element Design and Function �� 225 7.5 Vessel Elements Are Perforate Cells and the Main Water Conductors in Angiosperms �� 227 7.6 Vessel Element Side Walls Are Patterned for Strength and Water Movement �� 230 7.7 Most Vessel Elements End in a Perforation Plate and Are Connected to Another Vessel Element �� 236 7.8 Xylem Parenchyma Are Living Cells Involved in Xylem Metabolism and Protection �� 239 7.9 Chapter Review �� 240 References and Additional Readings �� 244

8 Phloem �� 247 8.1 Phloem Is a Complex Tissue Containing Multiple Cell Types, Each with a Specific Structure and Function �� 248 8.2 Phloem’s Main Function Is Photosynthate Translocation �� 251 8.3 Sieve Tube Elements Are Living Cells Responsible for Translocation �� 252 8.4 Companion Cells Support the Sieve Tube Element and Are Involved in Phloem Loading and Unloading in Angiosperms �� 258 8.5 Phloem Parenchyma Cells Are Involved in Radial Translocation, Xylem/Phloem Coordination, and Storage �� 260 8.6 Phloem Fibers Protect the Delicate Sieve Tubes �� 264 8.7 Secondary Phloem Typically Only Functions for One Growing Season �� 265 8.8 Gymnosperm Phloem Is Simpler Than Angiosperm Phloem �� 266 8.9 Girdling Inhibits Phloem Translocation and Can Kill a Tree �� 269 8.10 Chapter Review �� 270 References and Additional Readings �� 274

IV Primary Vegetative Growth

9 Epidermis �� 279 9.1 Pavement Epidermal Cells Cover Leaf and Stem Surfaces �� 280 9.2 Stomata Are Dynamic Pores That Control Gas Exchange �� 284 9.3 Guard Cells and Subsidiary Cells Make Up the Stomatal Complex �� 288 9.4 The Cuticular Membrane Protects the Plant Surface �� 295 9.5 Stomata Vary in Distribution and Depth �� 300 9.6 Trichomes Protect the Leaf from Biotic and Abiotic Stresses �� 303 9.7 Glandular Trichomes Secrete a Variety of Oils, Resins, and Toxins �� 306 9.8 Idioblasts Are Unusual Cells in the Epidermis and May Contain Elemental Deposits �� 309 9.9 Chapter Review �� 312 References and Additional Readings �� 318

10 Roots �� 319 10.1 Roots and Root Systems Serve Multiple Purposes �� 320 10.2 Root System Morphology Is Diverse and Adapts to Soil Conditions via Compensatory Growth �� 324 XIII Contents

10.3 Primary Growth of Roots Involves Formation of Tissues and Their Organization �� 327 10.4 The Root Tip and Root Cap Control Rate and Direction of Root Growth�� 328 10.5 The Root Rhizodermis Interacts Directly with the Soil �� 332 10.6 The Root Cortex, Limited by the Endodermis, Is a Site of Storage and Oxygen Transport �� 335 10.7 The Stele Contains the Pericycle and the Xylem and Phloem of the Vasculature �� 337 10.8 Lateral Roots Originate in the Pericycle and Push Through the Cortex �� 339 10.9 The Transition from Primary to Secondary Growth in Roots Involves the Development of Two New Meristems �� 342 10.10 Symbioses Between Roots/Bacteria and Roots/Fungi Greatly Enhance Nutrient Acquisition �� 343 10.11 Chapter Review �� 348 References and Additional Readings �� 353

11 Stems �� 355 11.1 Stems Have a Variety of Forms and Functions �� 356 11.2 External Stem Morphology Varies Among Monocots and Herbaceous Eudicots �� 360 11.3 The Stem Is Composed of Three Tissues: Dermal, Ground, and Vascular �� 364 11.4 Dermal Tissues Cover the Stem Exterior �� 366 11.5 Ground Tissues Compose the Cortex, Pith, and Conjunctive Tissue �� 367 11.6 Stem Vascular Tissues Are Arranged in Bundles �� 373 11.6.1 Relationship of Xylem to Phloem in Vascular Bundles �� 374 11.6.2 Patterns of Xylem Development in the Stem �� 376 11.6.3 Patterns of Phloem Development in the Stem �� 377 11.7 Evolutionary Advances Led to Variations in Stem Architecture �� 379 11.8 Secondary Growth in Eudicots Initiates in Three Basic Patterns �� 384 11.9 Monocot Stems Show a Different Form of Secondary Growth than Eudicots �� 385 11.10 Chapter Review �� 390 References and Additional Readings �� 394

12 Leaves �� 395 12.1 Leaves Have a Variety of Shapes and Functions �� 396 12.2 The Vascular System Spreads Throughout the Leaf �� 399 12.3 Leaf Morphology Is Optimized for Light Absorption, Gas Exchange, and Water Conservation �� 407 12.3.1 Typical Dorsiventral Eudicot Leaves �� 407 12.3.2 Variations in Palisade Parenchyma �� 409 12.3.3 Isobilateral and Unifacial Monocot Leaves �� 411 12.3.4 Centric Eudicot Leaves �� 413 12.3.5 Tubular Leaves �� 414 12.4 The Light Environment During Development Can Modify Leaf Anatomy �� 415

12.5 Kranz Leaf Anatomy Is a Specialization of the C4 Photosynthetic Pathway �� 417 12.6 Xeromorphic Angiosperm Leaves Conserve Water in Arid Environments �� 419 12.7 Succulent Leaves Are Adapted for Water Storage �� 423 12.8 Aquatic Angiosperms Have Hydromorphic Leaves �� 425 12.9 Xeromorphic Conifer Leaves Conserve Water During Winter �� 430 12.10 Leaf Abscission Is a Timed and Genetically Controlled Process �� 431 12.11 Chapter Review �� 436 References and Additional Readings �� 440 XIV Contents

13 Secretory Structures �� 443 13.1 External Secretion Involves Moving Substances to the Surface of the Plant �� 444 13.1.1 Glandular Trichomes �� 444 13.1.2 Colleters �� 445 13.1.3 Stinging Hairs �� 446 13.1.4 Nectaries �� 447 13.1.5 Hydathodes �� 450 13.1.6 Salt Glands �� 451 13.2 Carnivorous Plants Have Evolved External Secretory Structures as a Mechanism for Nutrient Acquisition �� 452 13.3 Internal Secretory Structures Include Oil Cavities, Resin Ducts, and Laticifers �� 458 13.3.1 Oil Cavities �� 458 13.3.2 Resin Ducts �� 458 13.3.3 Laticifers �� 460 13.4 Idioblasts Are Internal Secretory Cells That Contain Crystals, Cystoliths, or Tannins �� 462 13.4.1 Crystal Idioblasts �� 462 13.4.2 Cystoliths �� 465 13.4.3 Tannin-Containing Idioblasts �� 468 13.5 Essential Oils Are Valuable Plant Extracts �� 469 13.6 Toxic Oils Often Cause Severe Dermatitis �� 469 13.7 Chapter Review �� 471 References and Additional Readings �� 475

V Secondary Vegetative Growth

14 Vascular Cambium �� 479 14.1 The Vascular Cambium Is a Single-Layer Cylinder of Meristematic Cells �� 480 14.2 The Transition from Primary to Secondary Growth Requires Lateral Expansion of the Vascular Cambium �� 484 14.3 The Vascular Cambium Contains Two Types of Cells: Fusiform Initials and Ray Initials �� 484 14.4 Fusiform Initials Can Be Arranged in Different Patterns �� 490 14.5 Anomalous Vascular Cambia Produce Atypical Growth Patterns �� 490 14.5.1 Normal Location, Abnormal Activity �� 492 14.5.2 Normal Activity, Abnormal Location �� 493 14.5.3 Anomalous Secondary Growth in Roots �� 498 14.5.4 Spiral Growth in Eudicots �� 498 14.6 Grafting Relies on the Fusion of Active Vascular Cambia �� 500 14.7 Parasitic Plants Merge Their Vasculature with that of the Host Plant �� 502 14.8 Chapter Review �� 504 References and Additional Readings �� 507

15 Wood: Economics, Structure, and Composition �� 509 15.1 Wood Has Significant Worldwide Economic Value �� 511 15.2 A Wide Variety of Products Are Made from Wood Fibers and Wood Extracts �� 514 15.3 Wood Development and Composition Show Annual Cycles �� 516 15.4 Wood Varies in Its Architecture and Composition �� 518 15.4.1 Cross, Radial, and Tangential Planes of Section �� 518 15.4.2 Softwood vs. Hardwood �� 520 15.4.3 Sapwood vs. Heartwood �� 521 15.5 Conifer Wood Has Tracheids, Parenchyma, and Rays �� 522 XV Contents

15.6 Eudicot Wood Is Characterized by Vessel Elements, Tracheids, Parenchyma, and Rays �� 526 15.6.1 Patterns of Xylem Vessel Element Distribution �� 526 15.6.2 Vessel Grouping �� 527 15.6.3 Patterns of Xylem Parenchyma �� 529 15.6.4 Ray Architecture �� 531 15.7 Reaction Woods Develop in Response to Gravity �� 533 15.8 Tyloses and Crystals May Be Found in Some Woods �� 535 15.9 Monocot “Wood” Does Not Come from True Secondary Growth �� 537 15.10 Wood Macerations Are Useful for Species Identification, Product Identification, and Forensics �� 539 15.11 The Study of Tree Rings Is Important in Archeology, Climatology, and Forensics �� 540 15.12 Chapter Review �� 542 References and Additional Readings �� 551

16 Periderm �� 553 16.1 Periderm Comprises a Large Component of Bark and Adds a Protective Layer to Plants �� 554 16.2 Phellogens Originate De Novo by Dedifferentiation of Existing Cells in the Epidermis, Cortex, Phloem, or Pericycle �� 557 16.3 Phellem Cells Are Suberized, Dead, and Generated to the Exterior of the Phellogen �� 560 16.4 Phelloderm Cells Are Living and Generated to the Interior of the Phellogen �� 562 16.5 The Polyderm Is an Internal Protective Tissue Composed of Alternating Rows of Suberized and Lignified Cells �� 563 16.6 Lenticels Are Formed in Areas Where the Periderm Has Ruptured due to the Buildup of Filling Tissue, Facilitating Gas Exchange �� 563 16.7 The Rhytidome Is a Multiyear, Multilayered Accumulation of Dead Tissues �� 565 16.8 Cork Is a Commercially Important Rhytidome �� 568 16.9 Chapter Review �� 571 References and Additional Readings �� 575

VI Flowering and Reproduction

17 Flowers and Male Reproductive Structures �� 579 17.1 Flowers Possess Parts Arranged in Whorls That Vary Within and Among Species and Are Supported by a Receptacle �� 581 17.2 Floral Development Starts with Increasing Cell Divisions in Apical Meristems and Initiating Organs in an Acropetal Sequence �� 586 17.3 Male Reproductive Structures Give Rise to Pollen Within the Anther �� 589 17.4 Pollen Grain Formation Begins with Microsporogenesis Followed by Microgametogenesis �� 592 17.4.1 Microsporogenesis Is the Formation of Microspore Mother Cells �� 592 17.4.2 Microgametogenesis Results in the Development of the Microgametophyte: The Pollen Grain �� 593 17.4.3 The Tapetum Provides Nutrition and Substances to Form the Exine �� 596 17.5 The Structure of Pollen Grain Cell Walls Changes During Development from Microspore to Macrogametophyte, and Callose Is Deposited and Then Sporopollenin and Adhesives �� 597 17.6 The Surface Characteristics of Pollen Grains Are Taxon Specific �� 600 17.7 Pollen Dispersal, Germination, and Pollen Tube Growth Precede Double Fertilization �� 602 XVI Contents

17.8 Pollen Tube Growth Is Restricted to the Tip Region �� 604 17.9 Pollen Is a Major Contributor to Seasonal Allergies �� 608 17.10 Chapter Review �� 609 References and Additional Readings �� 613

18 Female Reproductive Structures and Embryogenesis �� 615 18.1 The Innermost Whorl of the Flower Is Typically Composed of Female Floral Parts �� 617 18.2 Ovaries Are Described Based upon Position Within a Flower and May Contain Nectaries �� 618 18.3 Ovules Can Be Arranged Within an Ovary in a Variety of Ways �� 620 18.4 Development of the Megagamete Begins with the Differentiation of the Megaspore Mother Cell and Ends with the Formation of the Megagametophyte (Embryo Sac) �� 624 18.5 Pollination Is Followed by Germination of the Pollen Grain and Pollen Tube Growth �� 629 18.6 Double Fertilization Results in a Triploid Endosperm and a Diploid Zygote �� 633 18.7 Postfertilization-to-Proembryo Phase Leads to the Formation of an Eight-Celled Embryo and Suspensor Whose Development Is Controlled by Circuit Elements �� 636 18.8 Early Embryo-to-Heart Transition Leads to the Specification of the Basic Body Plan Within the Embryo �� 637 18.9 The Last Phase of Embryogenesis Involves Organ Expansion and Maturation �� 638 18.10 The General Pattern of Embryogenesis Differs Between Eudicots and Monocots �� 641 18.11 Alternation of Generations Is Unique to Plants �� 642 18.12 Chapter Review �� 643 References and Additional Readings �� 648

19 Fruits, Seeds, and Seedlings �� 649 19.1 Fruits Are Highly Modified Ovaries �� 650 19.2 Fruit Classification Is Based on Characters, Not Necessarily Species Relatedness �� 651 19.3 Dry Fruits Are Often Hard, Containing Fused Pericarp Layers and Dead Cells �� 654 19.3.1 Indehiscent Dry Fruits �� 654 19.3.2 Dehiscent Dry Fruits �� 656 19.4 Fleshy Fruits Are Characterized by an Enlarged, Juicy Pericarp �� 659 19.5 Fruit Structure Can Include Aggregations of Flowers into One Fruit or Many Small Fruits Within a Larger Assembly �� 662 19.6 The Seed Is an Individual Plant Containing Nutrition for the Embryo �� 664 19.7 The Seed Coat Surrounds the Embryo and Storage Tissues �� 667 19.8 Germination of the Seed Occurs when Environmental Conditions Are Appropriate and Marks the “Birth” of the Individual Plant �� 671 19.9 Chapter Review �� 674 References and Additional Readings �� 678

Correction to: Plant Anatomy ��C1

Supplementary Information Appendix 1: Answers to End-of-Chapter Material �� 680 Glossary �� 696 Index �� 717