Plant Solute Transport

by Yeo, Anthony R.; Flowers, Timothy J.

• ISBN13: 9781405139953
• ISBN10: 1405139951
• Edition: 1st
• Format: Hardcover
• Copyright: 2007-04-23
• Publisher: Wiley-Blackwell

Summary

This book provides a broad overview of solute transport in plants. It first determines what solutes are present in plants and what roles they play. The physical bases of ion and water movement are considered. The volume then discusses the ways in which solutes are moved across individual membranes, within and between cells, and around the plant. Having dealt with the role of plant solutes in 'normal' conditions, the volume proceeds to examine how the use of solutes has been adapted to more extreme environments such as hot, dry deserts, freezing mountains and saline marshes. A crucial stage in the life cycle of most plants, the internally-controlled dehydration concomitant with seed formation, is also addressed. Throughout the volume the authors link our increasing understanding of the cellular and molecular bases of solute movement with the roles that these fulfil in the whole plant under both ideal and stressful conditions, showing how these are dictated by the physical laws that govern solute and water movement. The book is directed at postgraduates, researchers and professionals in plant physiology, biochemistry and molecular biology.

Author Biography

Dr Anthony Yeo and Professor Timothy Flowers, Department of Biology and Environmental Science, University of Sussex, Falmer, Brighton, UK

Table of Contents

Preface	p. xiii
Contributors	p. xvii
General introduction	p. 1
Introduction	p. 1
Synopsis	p. 3
Concluding remarks	p. 14
Reference	p. 14
Solutes: what are they, where are they and what do they do?	p. 15
Solutes: inorganic and organic	p. 15
Analysis of inorganic elements	p. 15
Obtaining material for analysis	p. 15
Optical methods	p. 16
Mass spectrometry	p. 16
X-ray fluorescence	p. 17
Ion-specific electrodes	p. 17
Ion chromatography	p. 17
Solute concentrations	p. 17
Organic compounds	p. 18
Range of solutes found in plants	p. 19
Localisation	p. 19
Stereological analysis	p. 19
Inorganic elements and electron microscopy	p. 20
Ion-specific microelectrodes	p. 21
Direct sampling	p. 22
Use of fluorescent dyes	p. 22
Flux analysis	p. 23
Organic compounds	p. 25
What do they do?	p. 25
Vacuoles	p. 25
Organelles and the cytoplasm	p. 26
Cell walls	p. 26
Conclusions	p. 26
References	p. 27
The driving forces for water and solute movement	p. 29
Introduction	p. 29
Water	p. 29
Free energy and the properties of solutions	p. 31
Free energy and chemical potential	p. 31
Water potential and water potential gradients	p. 32
Osmosis and colligative properties	p. 33
Cell water relations	p. 34
Water movement	p. 35
Water movement through the soil	p. 38
Water in cell walls	p. 39
Water movement across a root (or leaf)	p. 39
Water movement through the xylem and phloem	p. 40
Solute movement	p. 40
Chemical, electrical and electrochemical potentials and gradients	p. 41
Diffusion - Fick's first law	p. 41
Diffusion potential	p. 42
Nernst potential	p. 43
Donnan systems	p. 43
Goldmann equation	p. 44
Coupling of water and solute fluxes	p. 44
References	p. 45
Membrane structure and the study of solute transport across plant membranes	p. 47
Introduction	p. 47
Plant membranes	p. 47
Plant membrane composition	p. 47
Plant membrane structure	p. 50
Studying solute transport across plant membranes	p. 51
Transport techniques using intact or semi-intact plant tissue	p. 52
Plant growth	p. 52
Solution design	p. 52
Using inhibitors	p. 53
Accumulation and net uptake	p. 53
Radioactive tracers	p. 54
Fluorescent solute probes	p. 55
Electrophysiology	p. 57
Voltage-based measurements (membrane potential and ion concentration)	p. 58
Voltage clamping	p. 60
Using isolated membranes for transport studies	p. 60
Isolating membranes	p. 60
Assaying transport activities of protoplasts and membrane vesicles	p. 61
Using molecular techniques to inform transport studies	p. 63
Revealing the molecular identity of transporters and testing gene function	p. 63
Location of transport proteins	p. 64
Heterologous expression	p. 65
Combining techniques (an example of increasing resolution and physiological context)	p. 66
Future development	p. 66
Conclusions	p. 67
Acknowledgements	p. 67
References	p. 67
Transport across plant membranes	p. 75
Introduction	p. 75
Plant solutes	p. 76
Definitions and terminology	p. 76
Some formalisms	p. 79
Passive transport	p. 81
Diffusion through membranes	p. 81
Facilitated diffusion through carriers	p. 82
Transport through ion channels	p. 83
Potassium channels	p. 84
Calcium channels	p. 85
Non-selective ion channels	p. 85
Chloride channels	p. 85
Transport through water channels	p. 85
Primary active transport	p. 87
Primary proton pumps	p. 87
P-type ATPases	p. 88
V-type ATPases	p. 89
The pyrophosphatase	p. 90
Primary pumps involved in metal transport	p. 90
P-type Ca[superscript 2+] pumps	p. 90
Heavy metal ATPases	p. 91
ABC transporters	p. 92
Secondary active transport	p. 92
Potassium uptake	p. 93
Nitrate transport	p. 94
Sodium efflux	p. 95
Non H[superscript +]-coupled secondary transport	p. 95
Concluding remarks	p. 96
References	p. 96
Regulation of ion transporters	p. 99
Introduction	p. 99
Physiological situations requiring the regulation of ion transport	p. 99
Change of cell volume	p. 99
Nutrient acquisition	p. 102
Stress responses	p. 106
Molecular mechanism of regulation	p. 107
Transcriptional regulation	p. 108
Post-translational regulation	p. 109
Autoinhibition	p. 109
14-3-3 proteins	p. 111
Calmodulin	p. 113
Cyclic nucleotides	p. 114
Heteromerisation	p. 116
Traffic of ion transporters	p. 117
Conclusions and outlook	p. 120
References	p. 120
Intracellular transport: solute transport in chloroplasts, mitochondria, peroxisomes and vacuoles, and between organelles	p. 133
Introduction	p. 133
Research to identify solute transport proteins in plant organelles	p. 133
Benefits of a model plant: Arabidopsis thaliana	p. 134
Chloroplasts	p. 136
The function of plastids	p. 137
Transport across the outer envelope: general diffusion or regulated channels?	p. 137
A porin in the outer envelope of plastids?	p. 138
OEPs, a family of channels with substrate specificity	p. 138
Outer membrane channels and porins: evolutionary aspects in chloroplasts and mitochondria	p. 142
Transport across the inner envelope: phosphate translocators, major facilitators and carriers	p. 142
The phosphate translocator family	p. 142
Major-facilitator-mediated transport	p. 144
Carriers in the inner envelope of plastids	p. 146
Transport across the inner envelope: ABC transporters and ion transport	p. 147
ABC transporters	p. 147
Ion transport	p. 149
Transport of metal ions	p. 150
Mitochondria	p. 153
The function of plant mitochondria	p. 153
Transport across the outer membrane: the porin VDAC	p. 154
Transport across the inner membrane: carriers	p. 156
Transporters involved in ATP production	p. 156
Carriers for transport of TCA cycle intermediates	p. 158
Amino acid transport across mitochondrial membranes	p. 159
Carriers involved in [beta]-oxidation of fatty acids	p. 160
Transport across the inner membrane: ABC transporters and ion channels	p. 160
ABC transporters	p. 160
Ion channels	p. 161
Peroxisomes	p. 162
Function of peroxisomes in plant metabolism	p. 163
Solute transport across the peroxisomal membrane	p. 163
A porin in the peroxisomal membrane	p. 163
Specific transport proteins in the peroxisomal membrane	p. 165
Photorespiration: transport between plastids, mitochondria and peroxisomes	p. 166
Vacuoles	p. 167
Generating a pH gradient across the tonoplast: H[superscript +]-ATPase and H[superscript +]-pyrophosphatase	p. 168
Transport of malate and sucrose across the tonoplast	p. 170
Malate	p. 170
Sucrose	p. 171
Aquaporins and ABC transporter in the tonoplast	p. 171
Aquaporins in the vacuole are tonoplast-intrinsic proteins	p. 171
ABC transporters in the tonoplast	p. 172
Ion transport	p. 173
Ion channels	p. 173
Calcium, sodium and magnesium uptake involves active transport	p. 175
Transport of transition metals	p. 177
References	p. 178
Ion uptake by plant roots	p. 193
Introduction	p. 193
Soil composition	p. 193
Root exploration of the soil	p. 194
Physical factors affecting root uptake: depletion zones and Donnan potentials	p. 196
Radial transport of solutes across the outer part of the root	p. 197
The role of apoplastic barriers	p. 197
Root hairs and cortical cells	p. 198
Solute uptake from different root zones	p. 201
Transport of solutes to the xylem	p. 203
The kinetics of solute uptake into roots	p. 204
Radioisotopic studies	p. 204
Other methods	p. 207
Kinetics of uptake in response to solute availability	p. 207
Conclusion	p. 209
References	p. 209
Transport from root to shoot	p. 214
Introduction	p. 214
Transport of water	p. 214
Xylem structure	p. 214
Physics of water flow and evolutionary aspects of conduit development	p. 216
Water flow between xylem elements: safety mechanisms	p. 217
Hydraulics of the sap lift: general overview	p. 219
Driving force for water movement in the xylem	p. 221
Controversies and additional mechanisms	p. 222
Transport of nutrients	p. 224
General features of xylem ion loading	p. 224
Ionic mechanisms of xylem loading	p. 225
Potassium	p. 225
Sodium	p. 226
Anion channels	p. 227
Gating factors	p. 227
Xylem-sap composition	p. 228
Factors affecting ion concentration in the xylem	p. 229
Xylem unloading in leaves	p. 230
References	p. 231
Solute transport in the phloem	p. 235
Introduction	p. 235
Phloem anatomy	p. 236
Sieve tubes	p. 236
Sieve tubes are anucleate	p. 236
Sieve plate blockage	p. 237
Plasmodesmata	p. 238
Plasmodesmatal structure	p. 238
Plasmodesmatal selectivity	p. 238
Phloem composition	p. 240
Carbohydrate	p. 240
Sucrose	p. 240
Other carbohydrates	p. 240
Inorganic ions	p. 241
Variation in sieve element composition	p. 241
K[superscript +]/sucrose reciprocity	p. 242
Nitrogen	p. 242
mRNA	p. 243
Protein metabolism message	p. 244
Structural genes and cell-wall enzymes	p. 244
Interaction with DNA/RNA	p. 245
Carbohydrate metabolism	p. 245
Redox-oxidative stress	p. 245
Amino acid metabolism	p. 245
Transport	p. 245
Interaction with the environment	p. 246
Proteins	p. 246
Oxidative stress	p. 246
Defence	p. 247
Calcium and sieve element structure	p. 247
Metabolism	p. 247
Macromolecular trafficking	p. 248
Sieve element water relations	p. 248
Sieve element water relations	p. 249
Sieve element osmotic pressure	p. 249
Sieve element turgor pressure	p. 249
Flow in the phloem	p. 250
Phloem loading	p. 251
Symplastic or apoplastic loading?	p. 251
Transporters facilitating apoplastic loading	p. 254
H[superscript +]/ATPase	p. 255
Phloem unloading	p. 257
Evidence for unloading pathway: root tips	p. 257
Evidence for unloading pathway: developing fruits	p. 259
Evidence for unloading pathway: seed coats	p. 259
Resource partitioning through the phloem	p. 260
Exploitation by other organisms	p. 261
Micro-organisms and viruses	p. 261
Sap-feeding insects	p. 261
Plants	p. 262
Other organisms	p. 262
Conclusions	p. 262
References	p. 263
Factors limiting the rate of supply of solutes to the root surface	p. 275
Introduction	p. 275
Supply of nutrients to the root surface	p. 276
Absence of the nutrient element in the growth medium in any form	p. 276
Bioavailability of the element	p. 276
Movement of nutrients towards roots	p. 278
Homogeneity or heterogeneity (spatial and temporal) in availability	p. 279
Losses	p. 279
Acquisition and uptake of nutrients by the root	p. 280
Affinity and capacity of transport processes in the roots	p. 280
Exploration and exploitation of soil volume by roots	p. 282
Acquisition of phosphorus	p. 284
Protected cropping systems: hydroponics as an example of 'ideally' controlled conditions	p. 286
Concluding remarks	p. 287
References	p. 287
Mineral deficiency and toxicity	p. 290
Introduction	p. 290
Terminology	p. 291
Deficiency and efficiency: iron in alkaline soils	p. 293
'Strategy I': reduction-dependent iron uptake	p. 295
'Strategy II': phytosiderophores	p. 296
Phosphate uptake in soils that are low in phosphate	p. 299
Cluster roots and root exudates	p. 299
Mycorrhizal symbiosis	p. 300
Toxicity and tolerance-aluminium in acid soils	p. 301
Toxicity and tolerance-essential and non-essential metals	p. 303
Hyperaccumulation	p. 304
Ion transport in hyperaccumulators	p. 305
Phytochelatins	p. 306
Function of hyperaccumulation	p. 308
Concluding remarks	p. 308
References	p. 309
Water-limited conditions	p. 314
Introduction	p. 314
Plant responses to reduced water availability	p. 315
Mechanisms to reduce water loss: regulation of stomata and regulation of leaf area	p. 318
Stomatal regulation	p. 318
Leaf area regulation	p. 320
Consequences: interaction with leaf temperature	p. 321
Mechanisms to maintain water potential gradients: osmotic adjustment	p. 322
Water potential of drying soil	p. 322
Osmotic adjustment	p. 323
Compatible solutes/osmolytes/osmoprotectants	p. 324
Water movement from protoplast to apoplast in freezing injury	p. 326
Mechanisms to acquire more water: root properties	p. 326
Constitutive formation of deep roots	p. 326
Facultative formation of deep roots	p. 327
Root conductance	p. 327
Mechanisms to increase water-use efficiency: C4 and crassulacean acid metabolism (CAM)	p. 328
C4 photosynthesis	p. 329
CAM	p. 331
Gene regulation	p. 334
Concluding remarks	p. 335
References	p. 335
Salinity	p. 340
Introduction	p. 340
External concentration of salt up to about 50 mM NaCl	p. 341
External concentration of salt up to about 100-150 mM NaCl	p. 343
External concentration of salt above about 150-200 mM	p. 344
'Molecular' tolerance	p. 345
Cellular tolerance	p. 346
Moving on to a cell in a plant	p. 347
Salt glands	p. 347
Selectivity at the root	p. 348
Root selectivity for chloride	p. 353
Transport from root to shoot	p. 353
Transport of chloride to the xylem	p. 356
Transport from shoot to root	p. 356
Leaf cells	p. 357
Prospects	p. 361
Concluding remarks	p. 364
References	p. 365
Desiccation tolerance	p. 371
Introduction	p. 371
Occurrence of desiccation tolerance	p. 372
Desiccation tolerance in seeds	p. 372
Intracellular physical characteristics	p. 374
Intracellular de-differentiation	p. 374
'Switching-off' metabolism	p. 375
Antioxidant systems	p. 375
Protective molecules	p. 376
Amphiphilic molecules	p. 378
Oleosins	p. 379
Damage repair	p. 379
Vegetative tissues	p. 379
Gene expression	p. 382
Physical characteristics	p. 382
Metabolism and antioxidants	p. 383
Low-molecular-weight carbohydrates	p. 383
Hydrins or LEA proteins	p. 385
Signals	p. 385
Constraints to the development of desiccation tolerance	p. 386
Concluding remarks	p. 388
Acknowledgements	p. 388
References	p. 388
Index	p. 391
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