Air Plants

Air Plants: Epiphytes and Aerial Gardens

David H. Benzing
Copyright Date: 2012
Edition: 1
Published by: Cornell University Press,
Pages: 256
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  • Book Info
    Air Plants
    Book Description:

    Often growing far above the ground, "air plants" (or epiphytes) defy many of our common perceptions about plants. The majority use their roots only for attachment in the crowns of larger, usually woody plants-or to objects such as rocks and buildings-and derive moisture and nutrients from the atmosphere and by collecting falling debris. Only the mistletoes are true parasites. Epiphytes are not anomalies and there are approximately 28,000 species-about 10 percent of the higher or vascular plants-that grow this way. Many popular houseplants, including numerous aroids, bromeliads, ferns, and orchids, rank among the most familiar examples. In Air Plants, David H. Benzing takes a reader on a tour of the many taxonomic groups to which the epiphytes belong and explains in nontechnical language the anatomical and physiological adaptations that allow these plants to conserve water, thrive without the benefit of soil, and engage in unusual relationships with animals such as frogs and ants.

    Benzing's comprehensive account covers topics including ecology, evolution, photosynthesis and water relations, mineral nutrition, reproduction, and the nature of the forest canopy as habitat for the free-living and parasitic epiphytes. It also pays special attention to important phenomena such as adaptive trade-offs and leaf economics. Drawing on the author's deep experience with epiphytes and the latest scientific research, this book is accessible to readers unfamiliar with technical botany; it features a lavish illustration program, references, a glossary, and tables.

    eISBN: 978-0-8014-6387-7
    Subjects: Botany & Plant Sciences

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-x)
  3. Preface
    (pp. xi-xii)
  4. Acknowledgments
    (pp. xiii-xvi)
  5. 1 What Is an Epiphyte?
    (pp. 1-19)

    Different kinds of habitats host decidedly different kinds of plants. Species that live in deserts compared with those native to wetlands are adaptively distinct, and they in turn differ from those native to the understories of dense tropical forests. Hundreds of such ecologically defined categories exist, no small portion of which have already inspired book-length treatments. Other groups remain more obscure, and not necessarily because of small size or lack of importance. A particularly glaring omission is the absence for the nonspecialist of a comprehensive introduction to what are known as the “epiphytes.”

    Defined literally, an epiphyte is something that...

  6. 2 The Types of Epiphytes and Their Evolutionary Origins
    (pp. 20-41)

    Chapter 1 describes the epiphytes as operationally varied and taxonomically diverse. It also reports that some of the most specialized of their kind perform vital tasks in ways that differ from those practiced by plants that root in the ground. Especially noteworthy are the ways in which, under often difficult circumstances, many of the arboreal species obtain mineral nutrients, perform photosynthesis, and succeed in reducing the threat of drought to manageable proportions. Several of the quirkiest of these attributes position the epiphytes to play key roles in the lives of the other organisms that share their ecosystems.

    The ecological category...

  7. 3 Epiphytes in Communities and Ecosystems
    (pp. 42-65)

    Epiphytes are becoming increasingly popular choices for home, garden, and beyond. It’s common these days to spot a specimen or two in a friend’s home or brightening up a workplace. Professional displays are standard fare in airport concourses, shopping malls, and other public facilities. Encountering so many bromeliads, orchids, and others of their kind flourishing under such an array of artificial conditions can be misleading. Why so many of the epiphytes that you do not see are more challenging to grow should be evident after reading this chapter and the two that follow.

    Unlike the cultigens that owe their most...

  8. Color plates
    (pp. None)
  9. 4 Water Management
    (pp. 66-82)

    Introductory biology students often complain about having to cram their heads full of imminently forgettable facts. A few facts, however, aren’t so easily put aside, like the ones about water. Water makes up the bulk of our bodies, so the lesson goes, the actual number falling somewhere around 90–95%. The deeper message is certainly memorable: life for animals wouldn’t be possible were it not for this vital substance. Less often is it noted that the same lesson applies to plants.

    The land plants face countless challenges, but most threatening is the everpresent possibility of lethal desiccation. This is much...

  10. 5 Photosynthesis and Mineral Nutrition
    (pp. 83-97)

    Almost every kind of land-based habitat is at least moderately deficient in one or more of the resources that plants require. Drought has already been identified as the most pervasive of these challenges and especially for the epiphytes. Shade and shortages of key nutrients rank second and third. Plants are not uniformly prepared to deal with these environmental shortcomings, and not a single species can be described as superbly equipped to counter all three.

    The ways in which the epiphytes that experience arid conditions avoid serious dehydration, or minimize injury when they cannot, are described in Chapter 4. Members of...

  11. 6 Reproduction and Other Interactions with Animals
    (pp. 98-118)

    Evolution is a concerted process: when one group of organisms achieves a major adaptive breakthrough, others follow. Habitats suitable for airbreathing animals, for instance, could not exist until the higher plants had become well enough established on land to support them. Countless species have come and gone since this momentous event, but fauna still depend on flora for food and shelter.

    Over the course of the past 400 million years, the vascular plants and terrestrial animals have been forging increasingly complex interactions, many of which are not one sided the way herbivory is. Some benefit both participants, whereas others favor...

  12. 7 The Epiphytic Monocots
    (pp. 119-141)

    It is impossible to know how often epiphytism has evolved, but without doubt only a few of what presumably were many such events account for most of the living arboreal species. Fully two-thirds of the 28,000 modern epiphytes belong to a mere three families—all monocot-type angiosperms (Table 2.7; Figure 7.1). Ferns and lycophytes make up a sizable fraction of the rest, and what remains unassigned consists of non-monocot flowering plants augmented by just five gymnosperms.

    Why are the monocotyledonous families Araceae, Bromeliaceae, and especially Orchidaceae so inordinately successful in aerial habitats? Is this bias a statistical aberration—simply a...

  13. 8 The Epiphytic Eudicots
    (pp. 142-161)

    Although more than two-thirds of the flowering plants are eudicots, many fewer are epiphytic compared with the monocots (Table 2.7). Epiphytes comprise an even smaller fraction of the third and most primitive or basal of the three major groups of angiosperms. Except for a substantial portion of family Piperaceae, almost none of these oldest of the surviving flowering plants root above ground (Figure 7.1). The mistletoes are exclusively eudicotyledonous, and the vast majority belong either to family Loranthaceae or closely related Santalaceae.

    Two of the anatomical features that differentiate most of the eudicots from most of the monocots influence some...

  14. 9 The Pteridophytic Epiphytes
    (pp. 162-181)

    All the epiphytes surveyed so far produce seeds, which makes them “higher” vascular plants, or what botanists call spermatophytes. Now it is time to consider the roughly 12,000 kinds of pteridophytes. Because these species reproduce more like the aquatic antecedents of the entire vascular plant complex, they represent the more primitive or “lower” of its two “evolutionary grades.” The seed bearers are further differentiated into gymnosperms and the geologically younger angiosperms (flowering plants). The few thousand surviving gymnosperms in turn are divided among four subcategories: the conifers, the cycads, the relatively obscure “gnetaleans,” and Ginkgo biloba, the sole survivor of...

  15. 10 Miscellaneous Epiphytes
    (pp. 182-195)

    This final installment of our survey begins with Piperaceae, which is one of the basal angiosperm families because its antecedent stem linage branched off the main flowering plant line before those that gave rise to the modern or crown monocots and eudicots (Figure 7.1). Fuller analyses of the carnivorous epiphytes and primary hemi-epiphytes come next, followed by profiles of the few arboreal gymnosperms. The chapter ends with some additional families of flowering plants that seldom receive recognition as having epiphytic members.

    Piperaceae is the last to be considered of the families that contain hundreds or more epiphytes. It stands alone,...

  16. 11 Threats and Conservation
    (pp. 196-204)

    Conservationists paint a bleak picture of what lies ahead for the world’s most environmentally sensitive flora, a group that includes many of the epiphytes. Expanding urban development and mounting numbers of people and livestock are bound to continue the current wholesale destruction of tropical woodland habitats. Moreover, changing climates and artificially elevated supplies of two key plant nutrients will increasingly challenge whatever manages to escape this fate. It is hard to imagine, short of some stunning turn of human events, that more than a modest fraction of the surviving epiphytes will still be growing in the wild by the end...

  17. Glossary
    (pp. 205-218)
  18. References
    (pp. 219-224)
  19. Subject Index
    (pp. 225-234)
  20. Taxon Index
    (pp. 235-240)