Kaplan's Principles of Plant Morphology

Donald Kaplan, Chelsea D. Specht

• Publisher: CRC Press
• Year: 2022
• Print ISBN: 9781482245196
• eBook ISBN: 9781351644938
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

Kaplan's Principles of Plant Morphology defines the field of plant morphology, providing resources, examples, and theoretical constructs that illuminate the foundations of plant morphology and clearly outline the importance of integrating a fundamental understanding of plant morphology into modern research in plant genetics, development, and physiology. As research on developmental genetics and plant evolution emerges, an understanding of plant morphology is essential to interpret developmental and morphological data. The principles of plant morphology are being brought into studies of crop development, biodiversity, and evolution during climate change, and increasingly such researchers are turning to old texts to uncover information about historic research on plant morphology. Hence, there is great need for a modern reference and textbook that highlights past studies and provides the synthesis of data necessary to drive our future research in plant morphological and developmental evolution.

Key Features

• 
  
  

• Numerous illustrations demonstrating the principles of plant morphology

• 
  
  

• Historical context for interpretations of more recent genetic data

• 
  
  

• Firmly rooted in the principles of studying plant form and function

• 
  
  

• Provides evolutionary framework without relying on evolutionary interpretations for plant form

• 
  
  

• Only synthetic treatment of plant morphology on the market

Related Titles

Les, D. H. Aquatic Dicotyledons of North America: Ecology, Life History, and Systematics (ISBN 978-1-4822-2502-0)

Les, D. H. Aquatic Monotyledons of North America: Ecology, Life History, and Systematics (ISBN 978-1-1380-5493-6)

Bowes, B. G. Colour Atlas of Woody Plants and Trees (ISBN 978-0-3674-7398-3)

Bahadur, B. et al., eds. Asymmetry in Plants: Biology of Handedness (ISBN 978-1-1385-8794-6)

1 Introduction to the Science of Plant Morphology: Goals and Concepts

CONTENTS

• Examples of Higher Plant Structural Diversity and Life Forms
• Basic Organization of the Higher Plant Body
  • The Shoot System
  • The Root System
• The Concept of Homology
  • Homology Criteria
  • The Concepts of Analogy Versus Homology

Have you ever wondered as you stroll through a forest how the many varieties of plants are related to one another? How does a herb differ from a tree or what gives a vine its distinctive climbing characteristics? Are they radically different kinds of plants or do they share some common features? Questions such as these are addressed by the science of plant morphology.

The science of plant morphology deals with the external form of plants. The word morphology comes from the Greek words morphos meaning shape and logos meaning discourse. Since plant morphology is concerned principally with the structure and variation of the major plant organs (leaf, stem, and root), another term for its study is organography. In terms of the equivalent level of study of animals, plant morphology is comparable to animal anatomy, whereas plant anatomy, which is concerned with the cell to tissue levels of organization, is equivalent to animal histology. In this book our emphasis will be on the macroscopic aspects of plant structure, or what we can see largely with the unaided eye. We will make occasional excursions into the microscopic structure of plants, but only to analyze the origin and development of organs and organ components and where histology can tell us something about the status and function of a particular organ type.

All vascular plants (also known as tracheophytes) appear to be built on the same fundamental organizational theme or ground plan. Thus the vast majority of structural variants that we find occupying the many different habitats on earth today are simply variations on this basic theme. A fundamental goal of the science of plant morphology is to deduce this basic organizational theme from broad, comparative studies and to determine how variants come about through differences in plant growth and development.

The principal goals of this text are: 1) to teach the reader how to analyze the basic structural features of plants that are altered to produce the major variations in plant form and 2) to determine the significance of these morphological variants in the environments in which the plants grow. To these ends this book will first acquaint you with the science of plant morphology and the basic organ components of the plant body, how they originate during plant development, and what parameters are varied to produce the range of their morphological expression. Once you have acquired the ability to analyze plant morphology, we will apply these principles to plants that grow in particular kinds of habitats to see how form relates to function.

Before we delve into the specifics of how plants are constructed, let's look at some biologically interesting examples of the kinds of plants we are going to learn to analyze. While at first glance these species may seem simply weird and unrelated to your experience, by the time we come to consider them as individual vegetation types, you will see how even the most extreme representatives are related structurally to more conventional plant species that you are familiar with.

Examples of Higher Plant Structural Diversity and Life Forms

Among the most distinctive plant types are epiphytes, plants that grow on the surfaces of other plants (the term epiphyte comes from Greek root words epi meaning upon and phyte meaning plant). True epiphytes spend their entire lives up away from the earth's surface typically on one of the aerial branches of a forest tree or on the surfaces of some other elevated plant. In Figure 1.1, we see two epiphytic species which are members of the pineapple family, Bromeliaceae. Interestingly, taxonomically, they are both in the genus Tillandsia L. Tillandsia fasciculata Sw. has an upright shoot system, whereas, T. usneoides L., the well-known Spanish moss, has a highly branched shoot system that hangs down, forming an intertwining reticulum in the air. For both these epiphytes the particular environment in which they grow is a harsh one compared to life on the ground below. While they may be in an advantageous position with regard to incident light in the forest, such an aerial growth site is very poor in water and minerals. Plants of this type must exhibit structural and physiological specializations that permit them to scavenge the maximum available nutrients and water. The shoot surfaces of these two Tillandsia species are covered with specialized epidermal scales that take up water and minerals from the surrounding air (Benzing, 1970).

FIGURE 1.1 Two epiphytic species of Tillandsia growing on a tree branch in a Cypress swamp in southern Florida. Tillandsia fasciculata is the erect growing rosette shoot and T. usneoides, “Spanish moss,” is the much-branched, net-like species hanging below it.

Another epiphyte which exhibits quite different morphological specializations to cope with the rigors of this environment is the staghorn fern in the genus Platycerium (Figure 1.2). Platycerium climbs along its support plant, using its roots for attachment. It produces at least two different leaf types: large, elaborate pendant fronds which are the photosynthetic and spore-bearing organs of the shoot (FL, Figure 1.2) and mantle-type leaves which grow erectly and are heavily ribbed for reinforcement (ML, Figure 1.2). The mantle-type leaves catch water and debris from the trees above. In essence, the plant forms its own flowerpot, and its roots grow into the accumulated soil and water which are sources of nutrients in this otherwise nutrient-poor environment. We will see numerous other examples of particular plant groups that exhibit distinctly different but equally effective morphological solutions to similar environmental problems.

FIGURE 1.2 The staghorn fern in the genus Platycerium grows as an epiphyte along the trunk of a tropical forest tree. This species exhibits two types of leaves, the large branched and pendant foliage leaves (FL) which photosynthesize and bear the spores, and the mantle leaves (ML) that persist and impound debris as a source of nutrients for the roots of this fern to grow into.

It is an easy step to go from plants that live on the surfaces of other plants (epiphytes) but do not penetrate the tissues of their support plant and are nutritionally self-sufficient, to plants that actually penetrate the tissues of their host and are parasitic. Figure 1.3 shows an example of a parasitic flowering plant growing on a branch of a spruce tree, Picea spp. The parasite is the dwarf mistletoe Arceuthobium microcarpum (Engelm) Hawksw. & Wiens. While the aerial flowering shoots arising from the host surface may look conventional, in reality they are only the reproductive phase of this species. The vegetative or feeding phase consists of simplified strands that permeate the body of the host and draw water and nutrients from it. At the time of reproductive dispersal from the old host to a new one, the Arceuthobium initiates flowering shoots from the internal absorptive system. These flowering shoots break through the bark of the host to produce seeds, which are essential for dispersal of the parasite (Figure 1.3). Given Arceuthobium's nutritional dependence on its host, it is not necessary to have an elaborate vegetative structure differentiated into leaf and stem because this organism is no longer autotrophic. Such examples show us how closely plant structure and function can be linked in species with very specialized life modes.

FIGURE 1.3 The dwarf mistletoe Arceuthobium microcarpum growing as a parasite on a branch of a species of Spruce (Picea). The mistletoe shoots seen protruding from the surface of the host are actually the flowering portions of the parasite and are formed from the absorptive system inside the host tissues and secondarily break out onto its surface for pollination and seed dispersal. (From Hawksworth and Wiens, 1972.)

Certainly one of the most fascinating plant types are the so-called insectivorous or carnivorous plants. The thought that there can be such things as man (and woman)-eating plants has stirred the imaginations of science fiction writers since time immemorial. In reality, these plants are adapted to grow in areas that are deficient in certain mineral elements, especially nitrogen. Their plant bodies are specialized for the attraction, capture, and digestion of animals (mostly insects) as sources of nitrogen and other nutrients. An example is the shoot system of the California pitcher plant, Darlingtonia californica. This species has a rosette-type shoot with large, elaborately colored, tubular leaves that serve as traps and sites of digestion of the insects that nourish the plant. Despite the seemingly bizarre and unique functions that the leaves of this carnivore perform, their leaf morphology has been shown to be related to that of other, more conventional plants. Once we learn how to analyze plant form and understand the basis for its variation, such modified or functionally specialized organs will not seem quite so out of the ordinary.

One of the truly distinctive types of vegetation on the earth today are the mangroves. Mangroves are trees that grow along seacoasts and coral reefs in the tropical to subtropical latitudes. They are salt tolerant and are able to grow on relatively unstable substrates that can be covered by seawater during high tides. Because of the distinctive soil environment in which mangroves grow, it is their roots and root systems that exhibit specialization. Figure 1.4A shows an individual tree of the black mangrove, Avicennia germinans L. growing on the southwest coast of the Florida peninsula. If you observe this species at low tide, you will notice at the base of the trunk horizontally growing, cable-like roots that spread over the sandy substrate. Growing upward from these cable roots are erect, finger-like branches called pneumatophores (Figure 1.4B). When the rest of the root system is covered by saltwater at high tide, the pneumatophores protrude above the water and aerate the submerged roots. If you were to examine the structure of the pneumatophores microscopically you would see that they really are roots modified to function in this distinctive habitat.

FIGURE 1.4 A. Black mangrove tree Avicennia germinans growing on the south coast of Florida showing vertically growing root branches or pneumatophores exposed at low tide. B. Closeup view of pneumatophores growing upward from laterally extending strand roots. P, pneumatophore.

While we tend to think of plants as self-supporting structures whose shoots grow toward the light, vines and twining plants climb the surfaces of other plants to reach sufficient light. In contrast to epiphytes, vining plants begin their lives on the ground and only secondarily ascend their support plants. Many climbing plants have specialized branches or leaves that exhibit a particular physiological response called thigmotropism. Thigmotropism is a growth movement induced by the contact of a plant organ with some surface, usually the surface of another plant. Plant organs that exhibit a thigmotropic response are called te...

Table of contents

• Cover Page
• Half-Title Page
• Title Page
• Copyright Page
• Contents
• Preface
• Acknowledgments
• Authors
• 1. Introduction to the Science of Plant Morphology: Goals and Concepts
• 2. The Cast of Characters: A Review of the Plant Kingdom and Its Major Representatives
• 3. The Relationship between Morphology and Anatomy in Plants
• 4. Plant Embryogenesis: The Origin of Morphological Organization during Development
• 5. Early Plant Development: From Seed to Seedling to Established Plant
• 6. Divergent Patterns of Seedling Development and Their Significance for the Interpretation of Plant Ontogeny and Evolution
• 7. Phyllotaxis
• 8. The Concept of Differential Growth
• 9. The Effect of Internodal Elongation on Shoot Form
• 10. The Effect of Stem Thickening Growth on Shoot Form
• 11. Shoot Lateral Symmetry
• 12. Shoot Branching
• 13. Developmental Expressions and Specializations of Shoot Branches
• 14. Leaf Morphology and Development
• 15. Transectional Symmetry of Leaves
• 16. Longitudinal Symmetry and Zonation of Leaves Part I: Leaf Zones
• 17. Longitudinal Symmetry and Zonation of Leaves Part II: Blade Dissection
• 18. Specializations in Leaf Structure and Function
• 19. Morphology of Reproductive Shoots I: Pteridophytes
• 20. Morphology of Reproductive Shoots II: Gymnosperms
• 21. Morphology of Reproductive Shoots III. The Angiosperms A. The Floral Shoot
• 22. Morphology of Reproductive Shoots III. The Angiosperms B. The Floral Organs in Their Pre- and Post-Fertilization States
• 23. Morphology of Reproductive Shoots III. The Angiosperms C. Inflorescence Morphology
• 24. Principles of Root Morphology
• References
• Index