Structure-Function Relations of Warm Desert Plants

222 Pages·1996·7.043 MB·English

by  Dr. Arthur Charles Gibson (auth.)

Adaptations of Desert Organisms
Edited by J.L. Cloudsley-Thompson
Springer
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Volumes already published
Ecophysiology of the Camelidae and Desert Ruminants
By R.T. Wilson (1989)
Ecophysiology of Desert Arthropods and Reptiles
By J.L. Cloudsley-Thompson (1991)
Plant Nutrients in Desert Environments
By A. Day and K. Ludeke (1993)
Seed Germination in Desert Plants
By Y. Gutterman (1993)
Behavioural Adaptations of Desert Animals
By G. Costa (1995)
Invertebrates in Hot and Cold Arid Environments
By 1. S0mme (1995)
Energetics of Desert Invertebrates
By H. Heatwole (1996)
Ecophysiology of Desert Birds
By G.L. Maclean (1996)
Plants of Desert Dunes
By A. Danin (1996)
Biotic Interactions in Arid Lands
By J.L. Cloudsley-Thompson (1996)
Structure-Function Relations of Warm Desert Plants
By A.C. Gibson (1996)
In preparation
Physiological Ecology of North American Desert Plants
By S.D. Smith, R.K. Monson, and J.E. Anderson (1997)
Ecophysiology of Small Desert Mammals
By A.A. Degen (1997)
Ecophysiology of Amphibians Inhabiting Xeric Environments
By M.R. Warburg (1997)
Homeostasis in Desert Reptiles
By S.D. Bradshaw (1997)
Arthur C. Gibson
Structure-Function
Relations
of Warm Desert
Plants
With 75 Figures
i
Springer
Dr. Arthur Charles Gibson
Department of Biology
University of California, Los Angeles
Los Angeles, CA 90095-1606, USA
ISBN -13: 978-3-642-64638-6 e-ISBN -13: 978-3-642-60979-4
DOl: 10.10071978-3-642-60979-4
Library of Congress Cataloging-in-Publication Data Gibson, Arthur C. Structure-Function relations
of warm desert plants/Arthur C. Gibson. p. cm. (Adaptations of desert organisms) Includes bibli
ographical references and index. ISBN-13: 978-3-642-64638-6 1. Desert plants -
Adaptation. 2. Desert plants - Ecophysiology. 3. Desert plants - Anatomy. I. Title. II. Series.
OK922.G53 1996581.5'2652 - dc20
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Preface
Introductory biology textbooks cite plants of warm deserts, espe
cially cacti, as easily understood examples of natural selection.
Historically, these lessons to young biologists emphasize how a pe
culiar structural design relates to storing or conserving water, and
xerophyte and xeromorphic are now standard terms used to describe
plants adapted to dry environments. Numerous reviews on xero
phytism have been sources for such generalizations, but after criti
cally rereading those early reviews now we discover that the
conclusions were drawn mostly from species of semiarid vegetation
rather than from arid sites.
The field of physiological plant anatomy needs to take a long,
hard, fresh look at desert plant tissues, to distinguish desert struc
tural adaptations from those characterizing plants of semiarid habi
tats, and to reanalyze the physiological significance of such desert
designs. The current monograph focuses on plants oflowland trop
ical and subtropical arid deserts - for this exercise separated from
cool desert, dry scrubland, and steppe-and avoids describing
species that would be more typical of rocky upland desert sites. By
restricting analysis in this fashion, investigators will have the clear
est illustrations of structural adaptations to hot, nonfreezing, low
land environments. What readers will soon realize is that many
features formerly ascribed to plants of dry habitats are noticeably
rare in typical lowland desert plants!
To clarify basic anatomical properties of desert plants, this book
was restricted in coverage to vegetative adaptations, and, regrettably,
had to exclude reproductive adaptations from flowering through
seedling establishment. In this series, seed biology was already
treated in Seed Germination in Desert Plants (Gutterman 1993).
Numerous individuals have generously provided me with field
collected specimens from warm deserts, although admittedly my
own observations and those in the literature document less than
10% of the entire desert flora. The remainder forms a test for the
numerous hypotheses favored in this treatment. Thanks are due for
the important conceptual framework contributed to the field of
VI Preface
physiological anatomy from key researchers studying ecophysiol
ogy of desert plants.
Los Angeles, California A.C. GIBSON
June 1996
Contents
1 Plant Life Forms of Warm Desert Climates . 1
1.1 Distribution and Climates of Warm Deserts 1
1.2 Physiological Problems for Plants 3
1.2.1 Water and Heat Stress . . . . . 3
1.2.2 Soil Characters . . . . . . . . . 5
1.2.3 Wind and Flash-Flood Damage 6
1.3 Conceptual Models
for Desert Plant Adaptations 6
1.3.1 Xerophyte and Similar Terms 6
1.3.2 Stress Resistance . . . . 7
1.3.3 Carbon Gain Models . . 9
1.4 Plants of Warm Deserts 11
1.4.1 Floras and Endemism . 11
1.4.2 Primary Vegetation Types 12
1.4.3 Life Forms ....... . 13
1.4.3.1 Shrubs and Sub shrubs
with Drought-Deciduous Leaves 15
1.4.3.2 Evergreen Shrubs 16
1.4.3.3 Phreatophytes . . 16
1.4.3.4 Perennial Grasses 17
1.4.3.5 Ephemerals 18
1.4.3.6 Nonsucculent Aphyllous Shrubs and Trees 18
1.4.3.7 Stem and Leaf Succulents . . . . . . . 19
1.4.3.8 Poikilohydric Cryptogams. . . . . . . 21
1.4.3.9 Epiphytes and Mat-Forming Air Plants 21
1.4.3.10 Stem Mistletoes 21
1.4.4 Xerohalophytes ........... . 21
2 Functional Morphology
of Nonsucculent Leaves 23
2.1 Energy Balance of a Leaf 23
2.1.1 Absorptance as Influenced
by Organ Orientation and Reflectance 24
VIII Contents
2.1.2 Effects of Leaf Size and Form . . 26
2.1.3 Energy Storage
and Metabolic Heat Production 28
2.2 Leaf Size ...... . 28
2.2.1 Microphylly . . . . . . 28
2.2.2 Broad Desert Leaves 30
2.2.3 Seasonal Heteroblasty 32
2.3 Encelia as a Model System 32
2.4 Structural Nature of Surface Reflectance 37
2.5 Leaf Orientation and Display . . . 39
2.6 Leaf Rolling and Revolute Margins . . . 41
3 Physiological Anatomy
of Nonsucculent Leaves 45
3.1 Gas Diffusion Pathway 45
3.1.1 Water Vapor . . . . . 45
3.1.2 Carbon Dioxide . . . . 47
3.1.3 Flux Density of Gases . 47
3.1.4 Characteristics of Leaf Conductances 48
3.1.4.1 Leaf Boundary Layer Characteristics 48
3.1.4.2 Cuticle and Groundmass Epidermis. 49
3.1.4.3 Stomata ............ . 50
3.1.4.4 Intercelluar Air Spaces ...... . 52
3.1.4.5 Liquid-Phase Conduction of CO2 •• 52
3.1.5 Factors Limiting Photosynthetic Rates
at Saturated Photon Flux Density . 53
3.1.5.1 Relative Effects of Parameters . 53
3.1.5.2 C Physiology and Elimination
4
of Photo respiration . . . . . . 54
3.1.6 Water-Use Efficiency ..... 57
3.2 Physiological Anatomy of Nonsucculent Leaves
of Desert Plants . . . . . . . . . . . . . 58
3.2.1 Deciduous and Evergreen Shrubs . . . . 58
3.2.1.1 Groundmass Epidermis and Trichomes 58
3.2.1.2 Stomata ....... . 62
3.2.1.3 Mesophyll ............... . 67
3.2.2 Phyllodineous Acacias ........ . 75
3.2.3 Woody Dicotyledons with C Photosynthesis 76
4
3.3 Phreatophytes . . . . . . . . . 77
3.3.1 Desert Palms ........ . 77
3.3.2 Tropical Dicotyledonous Trees 78
3.3.3 Welwitschia mirabilis . . . . 79
3.3.4 Temperate Trees and Shrubs 80
Contents IX
3.3.5 Saltcedars and Casuarina . . . 80
3.4 Herbaceous Species . . . . . . 81
3.4.1 Perennial and Annual Grasses 81
3.4.2 Herbaceous Dicotyledons 83
3.4.3 Geophytes ..... . 88
3.4.4 Desert Springs . . . . 88
3.5 Fruit Photosynthesis 89
4 Photosynthetic Stems
of Nonsucculent Plants 91
4.1 Functional Morphology . 94
4.1.1 Energy Budget Considerations 94
4.1.2 Canopy Architecture and Phenology 95
4.2 Anatomy of Woody Plants. . . 100
4.2.1 Epidermis .......... . 100
4.2.1.1 Delay in Periderm Formation . 100
4.2.1.2 Composition. . . 100
4.2.1.3 Surface Coverings 101
4.2.1.4 Stomata ..... 103
4.2.2 Hypodermis . . . 104
4.2.3 Chlorenchyma and Associated Sclerenchyma 104
4.2.4 Leaf Anatomy . . . . . . . . . . . 109
4.3 Special Cases ........... . III
4.3.1 Bark Photosynthesis of Cercidium III
4.3.2 C Chenopodiaceae and Calligonum 112
4
4.3.3 Herbaceous Species . . . . . 113
4.3.3.1 Solid Stems and Grass Culms 113
4.3.3.2 Inflated Stems . . . . . . . . 114
5 Succulent Photosynthetic Organs 117
5.1 General Properties
of Succulent Photosynthetic Organs 117
5.1.1 Water Content . . . . . . . . . 119
5.1.2 High Volume-to-Surface Ratio ... 119
5.1.3 Crassulacean Acid Metabolism . . . 121
5.1.4 Epidermal Water Vapor Conductances 123
5.1.5 Stomatal Patterns . . 123
5.1.6 Chlorenchyma . . . . . . . 125
5.1.7 Succulent Hydrostats . . . 127
5.2 Taxon-Specific Adaptations 127
5.2.1 Aloe ........... . 127
x
Contents
5.2.2 Agave and Yucca. . . . 130
5.2.3 Windowed Leaves . . . 131
5.2.4 Epidermis of Aizoaceae 133
5.2.5 Areoles and Spines of Cacti 134
5.2.6 Euphorbiaceae
with CAM Stem Photosynthesis 136
5.2.7 Stapelieae . . . . . . . 136
5.2.8 Leaves of Crassulaceae .... . 137
5.2.9 Fouquieriaceae ........ . 137
5.2.10 Elephant Trees, Pachycauls, and Caudiciforms 140
5.2.11 Asteraceae . . 141
5.3 Fleshy Leaves ................ . 141
6 Special Topics in Water Relations . 143
6.1 Xerohalophytes . . . . . . . . . . 143
6.1.1 Vesiculated Trichomes of Atriplex 144
6.1.2 Excreting Salt Glands . . . . . . . 145
6.1.3 Halophytic Succulence ..... . 146
6.1.4 Nolana mollis and Other Atacaman Shrubs 146
6.1.5 Crystal Deposition in Shoots 147
6.2 Water Uptake . . . . . 147
6.2.1 Roots ........ . 147
6.2.1.1 Morphology and Depth 147
6.2.1.2 Structural Responses
to Drought and Rewetting . 149
6.2.2 Leaves and Stems . . . 152
6.2.2.1 Bromeliaceae ...... . 153
6.2.2.2 Selaginella lepidophylla
and Other Poikilohydric Plants 154
6.2.2.3 Water-Absorbing Stem Epidermis 155
6.2.3 Parasitic Vascular Plants 155
6.2.3.1 Mistletoes . . . . 155
6.2.3.2 Root Parasites . . 156
6.3 Vascular Tissues . 156
6.3.1 Veins in Leaves 156
6.3.2 Secondary Xylem 157
6.3.2.1 Shrubs and Sub shrubs
with Drought-Deciduous Leaves 159
6.3.2.2 Evergreen Shrubs . . . . . . . . 160
6.3.2.3 Phreatophytes . . . . . . . . . . 161
6.3.2.4 Nonsucculent Aphyllous Shrubs and Trees 163
6.3.2.5 Succulents . . . . . . . . . 163
6.3.2.6 Herbaceous Angiosperms . . . . . . . . . 165