Plant Physiological Ecology

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2 A. Photosynthesis. 10. 1 Introduction. 10. 2 General Characteristics of the Photosynthetic Apparatus. 10. 2.1 The Light and Dark Reactions of Photosynthesis. 10. 2.1.1 Absorption of Photons ..... 5 What Can We Extract from This Chapter? 455.

Hans Lambers Thijs L. Pons

F. Stuart Chapin III

Plant Physiological Ecology With 356 illustrations

Springer

Contents

Foreword by David T. Clarkson Acknowledgments Units and Conversions Abbreviations 1. Assumptions and Approaches

v vii ix xi 1

Introduction—History, Assumptions, and Approaches 1 What Is Ecophysiology? 2 The Roots of Ecophysiology 3 Physiological Ecology and the Distribution of Organisms 4 Time Scale of Plant Response to Environment 5 Conceptual and Experimental Approaches 6 New Directions in Ecophysiology 7 The Structure of the Book References and Further Reading

1 1 1 2 4 6 7 8 8

2. Photosynthesis, Respiration, and Long-Distance Transport

10

2 A. Photosynthesis 1 Introduction 2 General Characteristics of the Photosynthetic Apparatus 2.1 The Light and Dark Reactions of Photosynthesis 2.1.1 Absorption of Photons 2.1.2 Fate of the Excited Chlorophyll 2.1.3 Membrane-Bound Photosynthetic Electron Transport and Bioenergetics 2.1.4 Photosynthetic Carbon Reduction 2.1.5 Oxygenation and Photorespiration 2.2 Supply and Demand of CO2 in the Photosynthetic Process

10 10 10 10 12 12 13 13 14 14

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2.2.1 The CO2-Response Curve 2.2.2 Supply of CO2—Stomatal and Boundary Layer Conductances 2.2.3 The Internal Conductance Response of Photosynthesis to Light 3.1 Characterization of the Light Climate Under a Leaf Canopy 3.2 Physiological Biochemical, and Anatomical Differences Between Sun and Shade Leaves 3.2.1 The Light-Response Curve of Sun and Shade Leaves 3.2.2 Anatomy and Ultrastructure of Sun and Shade Leaves 3.2.3 Biochemical Differences Between Shade and Sun Leaves 3.2.4 The Light-Response Curve of Sun and Shade Leaves Revisited 3.2.5 The Environmental Signal for Shade Acclimation in Chloroplasts 3.3 Effects of Excess Irradiance 3.3.1 Photoinhibition—Protection by Carotenoids of the Xanthophyll Cycle 3.3.2 Chloroplast Movement in Response to Changes in Irradiance 3.4 Responses to Variable Irradiance 3.4.1 Photosynthetic Induction 3.4.2 Light Activation of Rubisco 3.4.3 Postillumination CO2 Assimilation and Sunfleck Utilization Efficiency 3.4.4 Metabolite Pools in Sun and Shade Leaves 3.4.5 Net Effect of Sunflecks on Carbon Gain and Growth Partitioning of the Products of Photosynthesis and Regulation by "Feedback" 4.1 Partitioning Within the Cell 4.2 Regulation of the Rate of Photosynthesis by Feedback • 4.3 Glucose Repression of Genes Encoding Calvin-Cycle Enzymes 4.4 Ecological Impacts Mediated by Source-Sink Interactions Responses to Availability of Water 5.1 Regulation of Stomatal Opening 5.2 The A-pi Curve as Affected by Water Stress 5.3 Carbon Isotope Discrimination in Relation to Water-Use Efficiency 5.4 Other Sources of Variation in Carbon Isotope Ratios in C3 Plants Effects of Soil Nutrient Supply, on Photosynthesis 6.1 The Photosynthesis-Nitrogen Relationship 6.2 Interactions of Nitrogen, Light, and Water 6.3 Photosynthesis, Nitrogen, and Leaf Lifespan Photosynthesis and Leaf Temperature: Effects and Adaptations 7.1 Effects of High Temperatures on Photosynthesis

15 20 21 25 26 26 26 29 30 34 35 36 40 41 42 42 43 44 44 46 46 46 47 50 50 50 52 53 54 54 56 56 57 57 58 58

Contents

2B.

xvii 7.2 Effects of Low Temperatures on Photosynthesis 8 Effects of Air Pollutants on Photosynthesis 9 C4 Plants 9.1 Introduction 9.2 Biochemical and Anatomical Aspects 9.3 Physiology of C4 Photosynthesis 9.4 Intercellular and Intracellular Transport of Metabolites of the C4 Pathway 9.5 Photosynthetic Nitrogen-Use Efficiency, Water-Use Efficiency, and Tolerance of High Temperatures 9.6 C3-C4 Intermediates 9.7 Evolution and Distribution of C4 Species 9.8 Carbon Isotope Composition of C4 Species 10 CAM Plants 10.1 Introduction 10.2 Physiological, Biochemical, and Anatomical Aspects 10.3 Water-Use Efficiency 10.4 Incomplete and Facultative CAM Plants 10.5 Distribution and Evolution of CAM Species 10.6 Carbon Isotope Composition of CAM Species 11 Specialized Mechanisms Associated with Photosynthetic Carbon Acquisition in Aquatic Plants 11.1 Introduction 11.2 The CO2 Supply in Water 11.3 The Use of Bicarbonate by Aquatic Macrophytes 11.4 The Use of CO2 from the Sediment 11.5 Crassulacean Acid Metabolism (CAM) in Water Plants 11.6 Variation in Carbon Isotope Composition Between Water Plants and Between Aquatic and Terrestrial Plants 11.7 The Role of Aquatic Macrophytes in Carbonate Sedimentation 12 Effects of the Rising CO2 Concentration in the Atmosphere 12.1 Acclimation of Photosynthesis to Elevated CO2 Concentrations 12.2 Effects of Elevated CO2 on TranspirationDifferential Effects on C3, C4, and CAM Plants 13 Summary: What Can We Gain from Basic Principles and Rates of Single-Leaf Photosynthesis? References and Further Reading

59 61 62 62 62 63

Respiration 1 Introduction 2 General Characteristics of the Respiratory System 2.1 The Respiratory Quotient 2.2 Glycolysis, the Pentose Phosphate Pathway, and the Tricarboxylic (TCA) Cycle 2.3 Mitochondrial Metabolism 2.3.1 The Complexes of the Electron-Transport Chain 2.3.2 A Cyanide-Resistant Terminal Oxidase 2.3.3 Substrates, Inhibitors, and Uncouplers 2.3.4 Respiratory Control 2.4^ A Summary of the Major Points of Control of Plant Respiration

96 96 96 96

66 66 68 70 72 72 72 73 78 78 78 80 80 80 80 81 82 82

83 85 86 86 89 89 89

98 98 98 99 100 101 102

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Contents

2C.

2.5 ATP Production in Isolated Mitochondria and In Vivo 2.5.1 Oxidative Phosphorylation: The Chemiosmotic Model 2.5.2 ATP Production In Vivo 2.6 Regulation of Electron Transport Via the Cytochrome and the Alternative Paths 2.6.1 Competition or Overflow? 2.6.2 The Intricate Regulation of the Alternative Oxidase 3 The Ecophysiological Function of the Alternative Path 3.1 Heat Production 3.2 Can We Really Measure the Activity of the Alternative Path? 3.3 The Alternative Path as an Energy Overflow 3.4 Using the Alternative Path in Emergency Cases 3.5 NADH-Oxidation in the Presence of a High Energy Charge 3.6 Continuation of Respiration When the Activity of the Cytochrome Path Is Restricted 4 Effects of Environmental Conditions on Respiratory Processes 4.1 Flooded, Hypoxic, and Anoxic Soils 4.1.1 Inhibition of Aerobic Root Respiration 4.1.2 Fermentation 4.1.3 Cytosol Acidosis 4.1.4 Avoiding Hypoxia: Aerenchyma Formation 4.2 Salinity and Water Stress 4.3 Nutrient Supply 4.4 Irradiance 4.5 Temperature 4.6 Low pH and High Aluminum Concentrations 4.7 Partial Pressures of CO2 4.8 Effects of Plant Pathogens 5 The Role of Respiration in Plant Carbon Balance 5.1 Carbon Balance 5.1.1 Root Respiration 5.1.2 Respiration of Other Plant Parts 5.2 Respiration Associated with Growth, Maintenance, and Ion Uptake 5.2.1 Maintenance Respiration 5.2.2 Growth Respiration 5.2.3 Respiration Associated with Ion Transport 5.2.4 Experimental Evidence 6 Plant Respiration: Why Should It Concern Us from an Ecological Point of View? References and Further Reading

102

Long-Distance Transport of Assimilates 1 Introduction 2 Major Transport Compounds in the Phloem: Why Not Glucose? 3 Phloem Structure and Function 3.1 Symplasmic and Apoplasmic Pathways of Phloem Loading

140 140

102 102 104 105 105 106 107 108 109 109 109 110 111 111 111 111 112 113 114 115 116 117 119 120 121 122 122 123 124 124 125 126 130 131 133 134

140 141 141

Contents

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3.2 Minor Vein Anatomy 3.3 Sugar Transport Against a Concentration Gradient 3.4 Variation in Transport Capacity 4 Phloem Loading and Ecological Distribution 5 Phloem Unloading 6 The Transport Problems of Climbing Plants 7 Summary: Phloem Loading, Plant Performance, and Plant Distribution References and Further Reading 3.

Plant Water Relations 1 Introduction 1.1 The Role of Water in Plant Functioning 1.2 Transpiration as an Inevitable Consequence of Photosynthesis 2 Water Potential 3 Water Availability in Soil 3.1 The Field Capacity of Different Soils 3.2 Water Movement Toward the Roots 3.3 Rooting Profiles as Dependent on Soil Moisture Content 3.4 Roots Sense Moisture Gradients and Grow Toward Moist Patches 4 Water Relations of Cells 4.1 Osmotic Adjustment 4.2 Cell-Wall Elasticity 4.3 Evolutionary Aspects 5 Water Movement Through Plants 5.1 General 5.2 Water in Roots 5.3 Water in Stems 5.3.1 Can We Measure Negative Xylem Pressures? 5.3.2 The Flow of Water in the Xylem 5.3.3 Cavitation or Embolism: The Breakage of the Xylem Water Column 5.3.4 Can Embolized Conduits Resume Their Function? 5.3.5 Trade-Off Between Conductance and Safety 5.3.6 Transport Capacity of the Xylem and Leaf Area 5.3.7 Storage of Water in Stems 5.4 Water in Leaves and Water Loss from Leaves 5.4.1 Effects of Soil Drying on Leaf Conductance 5.4.2 The Control of Stomatal Movements and Stomatal Conductance 5.4.3 Effects of Vapor Pressure Difference or Transpiration Rate on Leaf Conductance 5.4.4 Effects of Irradiance and CO2 on Leaf Conductance 5.4.5 The Cuticular Conductance and the Boundary Layer Conductance 5.4.6 Leaf Traits That Affect Leaf Temperature and Leaf Water Loss 5.4.7 Stomatal Control: A Compromise Between Carbon Gain and Water Loss 5.4.8 Water Storage in Leaves 5.5 Aquatic Angiosperms

146 146 147 149 150 151 151 152 154 154 154 155 156 158 159 160 162 162 163 163 164 166 167 167 169 172 172 174 175 177 178 179 180 181 182 185 185 189 190 190 191 193 194

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Contents

6 Water-Use Efficiency 7 Water Availability and Growth 8 Adaptations to Drought 8.1 Dessication-Avoidance: Annuals and Drought-Deciduous Species 8.2 Dessication-Tolerance: Evergreen Shrubs 8.3 "Resurrection Plants" 9 Winter Water Relations and Freezing Tolerance 10 Salt Tolerance 11 Final Remarks: The Message That Transpires References and Further Reading

198 199 199 201 203 203 204

Leaf Energy Budgets: Effects of Radiation and Temperature

210

4A. The Plant's Energy Balance 1 Introduction 2 Energy Inputs and Outputs 2.1 A Short Overview of a Leaf's Energy Balance 2.2 Short-Wave Solar Radiation 2.3 Long-Wave Radiation 2.4 Convective Heat Transfer 2.5 Evaporative Energy Exchange 2.6 Metabolic Heat Generation 3 Modeling the Effect of Components of the Energy Balance on Leaf Temperature—A Summary of Hot Topics References and Further Reading

210 210 210 210 211 214 214 216 217

4B.

221 221 221 221 221 221 223 223

Effects of Radiation and Temperature 1 Introduction 2 Radiation 2.1 Effects of Excess Irradiance 2.2 Effects of Ultraviolet Radiation 2.2.1 Damage by UV 2.2.2 Protection Against UV: Repair or Prevention 3 Effects of Extreme Temperatures 3.1 How Do Plants Avoid Damage by Free Radicals at Low Temperature? 3.2 Heat-Shock Proteins 3.3 Is Isoprene Emission an Adaptation to High Temperatures? 3.4 Chilling Injury and Chilling Tolerance 3.5 Carbohydrates and Proteins Conferring Frost Tolerance 4 Global Change and Future Crops References and Further Reading

5. Scaling-Up Gas Exchange and Energy Balance from the Leaf to the Canopy Level 1 Introduction 2 Canopy Water Use 3 Canopy CO2 Fluxes 4 Canopy Water-Use Efficiency 5 Canopy Effects on Microclimate: A Case Study

195 196 197

218 220

223 225 225 226 227 227 228

230 230 230 234 235 235

Contents

6 Aiming for a Higher Level References and Further Reading 6. Mineral Nutrition 1 Introduction 2 Acquisition of Nutrients 2.1 Nutrients in the Soil 2.1.1 Nutrient Supply Rate 2.1.2 Nutrient Movement to the Root Surface 2.2 Root Traits That Determine Nutrient Acquisition 2.2.1 Increasing the Roots' Absorptive Surface 2.2.2 Transport Proteins: Ion Channels and Carriers 2.2.3 Acclimation and Adaptation of Uptake Kinetics 2.2.3.1 Response to Nutrient Supply 2.2.3.2 Response to Nutrient Demand 2.2.3.3 Response to Other Environmental and Biotic Factors 2.2.4 Acquisition of Nitrogen 2.2.5 Acquisition of Phosphate 2.2.5.1 Plants Can Also Use Some Organic Phosphate Compounds 2.2.5.2 Excretion of Phosphate-Solubilizing Compounds 2.2.6 Changing the Chemistry in the Rhizosphere 2.2.6.1 Changing the Rhizosphere pH 2.2.6.2 Excretion of Organic Chelates 2.2.7 Rhizosphere Mineralization 2.2.8 Root Proliferation in Nutrient-Rich Patches: Is It Adaptive? 2.3 Sensitivity Analysis of Parameters Involved in Phosphate Acquisition 3 Nutrient Acquisition from "Toxic" or "Extreme" Soils 3.1 Acid Soils 3.1.1 Aluminum Toxicity 3.1.2 Alleviation of the Toxicity Symptoms by Soil Amendment 3.1.3 Aluminum Resistance 3.2 Calcareous Soils 3.3 Soils with High Levels of Heavy Metals 3.3.1 Why Are the Concentrations of Heavy Metals in Soil High? 3.3.2 Using Plants to Clean Polluted Water and Soil! Phytoremediation 3.3.3 Why Are Heavy Metals So Toxic to Plants? 3.3.4 Heavy-Metal-Resistant Plants 3.3.5 Biomass Production of Sensitive and Resistant Plants 3.4 Saline Soils: An Ever-Increasing Problem in Agriculture 3.4.1 Glycophytes and Halophytes 3.4.2 Energy-Dependent Salt Exclusion from Roots 3.4.3 Energy-Dependent Salt Exclusion from the Xylem 3.4.4 Transport of Na+ from the Leaves to the Roots and Excretion via Salt Glands 3.4.5 Compartmentation of Salt Within the Cell and Accumulation of Compatible Solutes

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237 237 239 239 239 240 240 241 245 245 246 248 248 249 251 252 253 253 253 257 257 259 260 260 263 266 266 267 269 269 271 272 272 272 273 273 276 277 277 278 278 279 280

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Contents

3.5 Flooded Soils 4 Plant Nutrient-Use Efficiency 4.1 Variation in Nutrient Concentration 4.1.1 Tissue Nutrient Concentration 4.1.2 Tissue Nutrient Requirement 4.2 Nutrient Productivity and Mean Residence Time 4.2.1 Nutrient Productivity 4.2.2 The Mean Residence Time of Nutrients in the Plant 4.3 Nutrient Loss from Plants 4.3.1 Leaching Loss 4.3.2 Nutrient Loss by Senescence 4.4 Ecosystem Nutrient-Use Efficiency 5 Mineral Nutrition: A Vast Array of Adaptations and Acclimations References and Further Reading

280 282 282 282 284 284 284 286 287 287 288 289 291 292

7. Growth and Allocation 299 1 Introduction: What Is Growth? 299 2 Growth of Whole Plants and Individual Organs 299 2.1 Growth of Whole Plants 300 2.1.1 A High Leaf Area Ratio Enables Plants to Grow Fast 300 2.1.2 Plants with High Nutrient Concentrations Can Grow Faster 301 2.2 Growth of Cells 301 2.2.1 Cell Division and Cell Expansion: The Lockhart Equation 301 2.2.2 Cell-Wall Acidification and Removal of Calcium Reduce Cell-Wall Rigidity 302 2.2.3 Cell Expansion in Meristems Is Controlled by Cell-Wall Extensibility and Not by Turgor 303 2.2.4 The Physical and Biochemical Basis of Yield Threshold and Cell-Wall Yield Coefficient 306 2.2.5 The Importance of Meristem Size 306 3 The Physiological Basis of Variation in RGR—Plants Grown with Free Access to Nutrients 306 3.1 SLA Is a Major Factor Associated with Variation in RGR 307 3.2 Leaf Thickness and Leaf-Mass Density 308 3.3 Anatomical and Chemical Differences Associated with Leaf-Mass Density 308 3.4 Net Assimilation Rate, Photosynthesis, and Respiration 309 3.5 RGR and the Rate of Leaf Elongation and Leaf Appearance 310 3.6 RGR and Activities Per Unit Mass 310 3.7 RGR and Suites of Plant Traits 310 4 Allocation to Storage 312 4.1 The Concept of Storage 312 4.2 Chemical Forms of Stores 313 4.3 Storage and Remobilization in Annuals 313 4.4 The Storage Strategy of Biennials 314 4.5 Storage in Perennials 314 4.6 Costs of Growth and Storage: Optimization 315 5 Environmental Influences 316 5.1 Growth as Affected by Irradiance 317 5.1.1 Growth in Shade 317 5.1.1.1 Effects on Growth Rate, Net Assimilation Rate, and Specific Leaf Area 317

Contents

5.1.1.2 5.1.1.3

Adaptations to Shade Stem and Petiole Elongation: The Search for Light 5.1.1.4 The Role of Phytochrome 5.1.1.5 Phytochrome and Cryptochrome: Effects on Cell-Wall Elasticity Parameters 5.1.1.6 Effects of Total Level of Irradiance 5.1.2 Effects of the Photoperiod 5.2 Growth as Affected by Temperature 5.2.1 Effects of Low Temperature on Root Functioning 5.2.2 Changes in the Allocation Pattern 5.3 Growth as Affected by Soil Water Potential and Salinity 5.3.1 Do Roots Sense Dry Soil and Then Send Signals to the Leaves? 5.3.2 ABA and Leaf Cell-Wall Stiffening 5.3.3 Effects on Root Elongation 5.3.4 A Hypothetical Model That Accounts for Effects of Water Stress on Biomass Allocation 5.4 Growth at a Limiting Nutrient Supply 5.4.1 Cycling of Nitrogen Between Roots and Leaves 5.4.2 Hormonal Signals That Travel via the Xylem to the Leaves 5.4.3 Signals That Travel from the Leaves to the Roots 5.4.4 Integrating Signals from the Leaves and the Roots 5.4.5 Effects of Nitrogen Supply on Leaf Anatomy and Chemistry 5.4.6 Nitrogen Allocation to Different Leaves, as Dependent on Incident Irradiance 5.5 Plant Growth as Affected by Soil Compaction 5.5.1 Effects on Biomass Allocation: Is ABA Involved? 5.5.2 Changes in Root Length and Diameter: A Modification of the Lockhart Equation 5.6 Growth as Affected by Soil Flooding ' 5.6.1 The Pivotal Role of Ethylene 5.6.2 Effects on Water Uptake and Leaf Growth 5.6.3 Effects on Adventitious Root Formation 5.7 Growth as Affected by Touch and Wind 5.8 Growth as Affected by Elevated Concentrations of CO2 in the Atmosphere 6 Adaptations Associated with Inherent Variation in Growth Rate 6.1 Fast-Growing and Slow-Growing Species 6.2 Growth of Inherently Fast- and Slow-Growing Species Under Resource-Limited Conditions 6.2.1 Growth at a Limiting Nutrient Supply 6.2.2 Growth in the Shade 6.3 Are There Ecological Advantages Associated with a High or Low RGR? 6.3.1 Various Hypotheses 6.3.2 Selection on RGRmax Itself, or on Traits That Are Associated with RGRmax? 6.3.3 An Appraisal.of Plant Distribution Requires Information on Ecophysiology 7 Growth and Allocation: The Messages about Plant Messages References and Further Reading

320 320 321 321 322 323 323 323 324 326 326 327 327 328 328 328 329 330 330 331 331 333 333 333 334 335 336 336 337 338 340 340 341 341 341 341 341 342 343 343 345

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8. Life Cycles: Environmental Influences and Adaptations 1 Introduction 2 Seed Dormancy and Germination 2.1 Hard Seed Coats . 2.2 Germination Inhibitors in the Seed 2.3 Effects of Nitrate 2.4 Other Chemical Signals 2.5 Effects of Light 2.6 Effects of Temperature ' 2.7 Physiological Aspects of Dormancy 2.8 Summary of Ecological Aspects of Seed Germination and Dormancy 3 Developmental Phases 3.1 Seedling Phase 3.2 Juvenile Phase . 3.2.1 Delayed Flowering in Biennials 3.2.2 Juvenile and Adult Traits 3.2.3 Vegetative Reproduction 3.2.4 Delayed Greening During Leaf Development in Tropical Trees • . •• 3.3 Reproductive Phase 3.3.1 Timing by Sensing Daylength: Long-Day and Short-Day Plants 3.3.2 Do Plants Sense the Difference Between a Certain Daylength in Spring and Autumn? 3.3.3 Timing by Sensing Temperature: Vernalization 3.3.4 Effects of Temperature on Plant Development 3.3.5 Attracting Pollinators 3.4 Fruiting • . ; 4 Seed Dispersal 4.1 Dispersal Mechanisms 4.2 Life-History Correlates 5 The Message to Disperse: Perception, Transduction, and Response References and Further Reading

352 352 352 353 353 354 355 355 359 360

9. Biotic Influences

378

9A. Symbiotic Associations 1 Introduction 2 Mycorrhizas 2.1 Endo- and Ectomycorrhizas: Are They Beneficial for Plant Growth? 2.1.1 The Infection Process . 2.1.2 Mycorrhizal Dependency 2.2 Nonmycorrhizal Species and Their Interactions with Mycorrhizal Species 2.3 Phosphate Relations 2.3.1 Mechanisms That Account for Enhanced Phosphate Absorption by Mycorrhizal Plants 2.3.2 Suppression of Colonization at High Phosphate Availability ' 2.4 Effects on Nitrogen Nutrition 2.5 Effects on the Acquisition of Water , 2.6 Carbon Costs of the Mycorrhizal Symbiosis -

361 362 362 363 364 365 366 367 368 368 369 370 370 370 371 374 374 374 374 375

378 378 378 379 379 384 384 384 384 386 387 390 390

Contents

2.7 Agricultural and Ecological Perspectives 3 Associations with Nitrogen-Fixing Organisms 3.1 Symbiotic N2 Fixation Is Restricted to a Fairly Limited Number of Plant Species 3.2 Host-Guest Specificity in the Legume-Rhizobium Symbiosis 3.3 The Infection Process in the Legume-Rhizobium Association 3.3.1 The Role of Flavonoids 3.3.2 Rhizobial nod Genes 3.3.3 Entry of the Bacteria Through Root Hairs 3.3.4 Final Stages of the Establishment of the Symbiosis 3.4 Nitrogenase Activity and Synthesis of Organic Nitrogen 3.5 Carbon and Energy Metabolism of the Nodules 3.6 Quantification of N2 Fixation In Situ 3.7 Ecological Aspects of the Nonsymbiotic Association with N2-Fixing Microorganisms 3.8 Carbon Costs of the Legume-Rhizobium Symbiosis 3.9 Suppression of the Legume-Rhizobium Symbiosis at Low pH and in the Presence of a Large Supply of Combined Nitrogen 4 Endosymbionts 5 Plant Life among Microsymbionts References and Further Reading 9B. Ecological Biochemistry: Allelopathy and Defense Against Herbivores 1 Introduction 2 Allelopathy 3 Chemical Defense Mechanisms 3.1 Defense Against Herbivores 3.2 Qualitative and Quantitative Defense Compounds 3.3 The Arms Race of Plants and Herbivores 3.4 How Do Plants Avoid Being Killed by Their Own Poisons? 3.5 Secondary Metabolites for Medicines and Crop Protection 4 Environmental Effects on the Production of Secondary Plant Metabolites 4.1 Abiotic Factors 4.2 Induced Defense and Communication Between Neighboring Plants 4.3 Communication Between Plants and Their Bodyguards 5 The Costs of Chemical Defense 6 Secondary Chemicals and Messages That Emerge from This Chapter , References and Further Reading 9C. Effects of Microbial Pathogens 1 Introduction 2 Constitutive Antimicrobial Defense Compounds

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392 392 392 393 394 395 395 396 398 399 399 401 403 404 405 406 407 408

413 413 413 415 415 418 418 422 424 427 427 428 430 431 433 433 437 437 437

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3 The Plant's Response to Attack by Microorganisms 4 Messages from One Organism to Another References and Further Reading

439 443 443

9D. Parasitic Associations 1 Introduction 2 Growth and Development 2.1 Seed Germination 2.2 Haustoria Formation 2.3 Effects of the Parasite on Host Development 3 Water Relations and Mineral Nutrition 4 Carbon Relations 5 What Can We Extract from This Chapter? References and Further Reading

445 445 446 446 447 451 452 454 455 456

9E. Interactions among Plants 1 Introduction 2 Theories of Competitive Mechanisms 3 How Do Plants Perceive the Presence of Neighbors? 4 Relationship of Plant Traits to Competitive Ability 4.1 Growth Rate and Tissue Turnover 4.2 Allocation Pattern, Growth Form, and Tissue Mass Density 4.3 Plasticity 5 Traits Associated with Competition for Specific Resources 5.1 Nutrients 5.2 Water 5.3 Light 5.4 Carbon Dioxide 6 Positive Interactions among Plants 7 Plant-Microbial Symbiosis 8 Succession 9 What Do We Gain from This Chapter? References and Further Reading

458 458 463 463 466 466

9F.

487 487

Carnivory 1 Introduction 2 Structures Associated with the Catching of the Prey and Subsequent Withdrawal of Nutrients from the Prey 3 Some Case Studies 3.1 Dionaea muscipula 3.2 Utricularia 3.3 The Tentacles of Drosera 4 The Message to Catch References and Further Reading

10. Role in Ecosystem and Global Processes 10A. Decomposition 1 Introduction 2 Litter Quality and Decomposition Rate 2.1 Species Effects on Litter Quality: Links with Ecological Strategy 2.2 Environmental Effects on Decomposition

469 470 472 472 474 475 475 476 477 480 481 483

487 489 489 490 491 492 494 495 495 495 495 495 497

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xxvii

3 The Link Between Decomposition Rate and Nutrient Mineralization 3.1 Effects of Litter Quality on Mineralization 3.2 Root Exudation and Rhizosphere Effects 4 The End-Product of Decomposition References and Further Reading

497 497 498 499 501

10B. Ecosystem and Global Processes: Ecophysiological Controls 1 Introduction 2 Ecosystem Biomass and Productivity 2.1 Scaling from Plants to Ecosystems 2.2 Physiological Basis of Productivity 2.3 Disturbance and Succession 2.4 Photosynthesis and Absorbed Radiation 2.5 Net Carbon Balance of Ecosystems 2.6 The Global Carbon Cycle 3 Nutrient Cycling 3.1 Vegetation Controls over Nutrient Uptake and Loss 3.2 Vegetation Controls over Mineralization 4 Ecosystem Energy Exchange and the Hydrologic Cycle 4.1 Vegetation Effects on Energy Exchange 4.1.1 Albedo 4.1.2 Energy Partitioning 4.1.3 Surface Roughness 4.2 Vegetation Effects on the Hydrologic Cycle 5 Scaling from Physiology to the Globe References and Further Reading

503 503 503 503 503 506 506 508 509 511 511 511 512 512 512 513 514 514 515 515

Glossary Index

518 533