ISBN: 3-540-52572-6
TITLE: Plants in the Deserts of the Middle East
AUTHOR: Batanouny, Kamal H.
TOC:

1 Introduction 1 
2 Deserts of the Middle East 5 
3 Climatic Aridity in the Deserts of the Middle East 11 
3.1 Rainfall 11 
3.2 Air Temperature 19 
3.3 Air Humidity and Evaporation 21 
3.4 Types of Climate 22 
4 Topography and Plant Life 25 
5 Plants in the Arabic Heritage 31 
6 Adaptations of Desert Plants 39 
6.1 What is Adaptation? 39 
6.2 Why Adaptation? 41 
6.3 What to Adapt to? 43 
7 Adaptations That Increase Water Absorption 45 
7.1 Adaptations of the Root System 45 
7.2 Characteristics of the Root Systems of Desert Plants 46 
7.2.1 Rapid Growth in the Seedling Stage 46 
7.2.2 Root Extension 50 
7.2.3 Low Shoot/Root Ratio 51 
7.2.4 Stratification 52 
7.2.5 Sparsity of Root Systems Within the Soil: Absence of Root Competition 53 
7.2.6 Plasticity of Responses to Soil Conditions 54 
7.2.7 Production of Adventitious Roots in Hillocks (Shoot-Borne Roots) 56 
7.2.7.1 Formation of Phytogenic Hillocks 56 
7.2.8 Production of Ephemeral Roots (Shoot-Borne Roots) 58 
7.2.9 Sheath Roots (Rhizosheaths) 58 
7.2.10 Resistance to Exposure Due to Wind Erosion 59 
7.2.11 Absorption from a Relatively Dry Soil 60 
7.2.12 Burial of Plants by Wind and Allocation of Resources 61 
7.2.13 Anatomical Features Enabling the Root to Tolerate Edaphic Aridity 62 
8 Adaptations That Reduce Water Loss 65 
8.1 Reduction of the Transpiring Body 66 
8.1.1 Shedding Part of the Green Cortex 67 
8.1.2 Shedding, Partly or Wholly, of Branches 71 
8.1.3 Leaf Shedding 72 
8.1.4 Shedding Winter Leaves and Retention of Summer Leaves 74 
8.2 Reduction of Transpiration 77 
8.2.1 Daily Reduction of the Transpiration Rate 80 
8.2.2 Seasonal Reduction in Transpiration Rate 87 
8.2.3 Reduction in Water Output of Individual Plants 88 
8.2.4 Reduction of Water Output from Natural Vegetation 89 
8.2.5 Reduction of Water Output at the Community Level 93 
8.2.5.1 Species Diversity 93 
8.2.5.2 Diversity of Life Forms 94 
8.2.5.3 Growth Form Diversity 96 
8.2.5.4 Physiological Diversity 96 
8.2.5.5 Intraseasonal Diversity 98 
8.2.5.6 Allelopathy in Desert Plants 98 
8.2.2 Plasticity of Transpiration Rates in Different Microhabitats 99 
9 Adaptational Traits That Resist and/or Tolerate Drought 103 
9.1 Introduction 103 
9.2 Physiological Adaptations 104 
9.2.1 Stomatal Control 104 
9.2.2 Bound Water 106 
9.2.3 Allocation of Resources 106 
9.2.4 The Accumulation of Proline and Other Amino Acids 108 
9.2.5 Photosynthetic Pathways 110 
9.2.5.1 Traits of C_4 Plants 110 
9.2.6 Osmotic Potential 112 
9.2.7 Protoplasmic Characteristics 114 
9.2.8 Response to Heat Stress 115 
9.2.9 Dew Absorption: Foliar Uptake of Water 116 
9.3 Anatomical Adaptations 118 
9.3.1 Anatomical Features 118 
9.3.2 Types of Anatomical Structures in Desert Plants 121 
9.3.3 Shedding of the Cortex 125 
9.3.4 Formation of Interxylary Cork 126 
9.3.5 Cell Size 126 
10 Adaptations That Engender Escape from Drought 127 
10.1 Drought Avoidance 127 
10.2 Winter Annuals 128 
10.2.1 Potential Annuals 130 
10.3 Geophytes 131 
10.4 Diminutive Perennials 132 
11 Adaptation to Desiccation 135 
11.1 Resurrection Plants 135 
11.2 Desert Poikilohydrous Thallophytes 136 
11.2.1 Algae 137 
11.2.2 Lichens 137 
11.2.2.1 Water Uptake by Lichens 139 
11.2.2.2 Lichens and Air Temperature 141 
11.2.3 Bryophytes 142 
11.2.4 Ferns 143 
12 Adaptations of Plants to Saline Conditions in Arid Regions 146 
12.1 Saline Regions and Halophytes 146 
12.2 Adaptations and Mechanisms 147 
12.3 Salt Excretion 149 
12.3.1 Salt Glands 149 
12.3.1.1 Structure of Salt Glands 149 
12.3.1.2 Ecological Factors Affecting Salt Secretion 152 
12.3.2 Salt Bladders and Hairs 152 
12.4 Shedding of Salt-Saturated Tissues and Organs 154 
12.5 Osmotic Adjustment 157 
12.6 Succulence 158 
12.7 Proline and Other Organic Metabolites 159 
12.8 Photosynthetic Pathways 160 
12.9 Germination and Vegetative Reproduction 162 
12.10 Formation of Phytogenic Mounds 164 
References 167 
Index of Latin Plant Names 183 
Index of Arabic Plant Names xxx 
Subject Index xxx 
END
