Science and the Garden

Preface to third edition, xiii Preface to second edition, xiv Preface to first edition, xv 1 Diversity in the plant world, 1 Summary, 1 Introduction, 1 Creating order out of disorder, 1 Colonisation of the land, 4 Communities and the diversity of life forms, 6 Conclusion, 12 Further reading, 13 Authors and affiliations, 13 2 The plant body: structure and function, 14 Summary 14 Introduction, 14 Energy flow in the biosphere: photosynthesis and respiration, 14 The light reaction of photosynthesis, 14 The dark reaction of photosynthesis, 14 C-3, C-4 and CAM plants, 14 Respiration, 16 Photorespiration, 16 Global significance of photosynthesis, 16 The leaf: into the labyrinth, 17 The manufacturing centre, 17 Cells, 17 Water relations of cells, 17 Layout of the leaf, 17 Controlling gas and water exchange, 17 Protection against harmful radiation, 19 Palisade tissues: the sites of photosynthesis, 21 The transport system, 21 Movement of water, minerals and hormones in the xylem, 21 Transport of carbohydrates and hormones in the phloem, 22 Producing new xylem and phloem: the cambium, 24 The bundle sheath, 24 Connecting with the stem, 25 Leaf fall, 25 Leaf patterns: phyllotaxy, 26 Variations on a theme, 26 The stem: reach for the sky, 27 The growing point, 27 Forming new leaves, 28 A tower of strength, 28 Secondary thickening: the formation of wood and bark, 29 Bark, 30 Stem modifications, 31 The root: mining for minerals and water, 32 The structure and growth of the root, 32 Storage roots and other modifications, 33 Nitrogen fixation, 34 Mycorrhizas, 34 Conclusion, 35 Further reading, 36 Authors and affiliations, 36 3 Reproduction: Securing the future, 37 Summary, 37 Introduction, 37 Vegetative reproduction, 37 Sexual reproduction, 38 Cones and flowers, 38 Alternation of generations, 41 Floral diagrams and formulae, 41 Seeds and fruits, 42 Other fruits, 42 Conclusion, 44 Further reading, 44 Authors and affiliations, 44 4 Naming plants, 45 Summary, 45 Introduction, 45 Latin botanical names, 45 Taxonomy: order in diversity, 47 New developments, 47 Cultivated plant taxonomy, 48 Distinctiveness, 49 Uniformity, 49 Stability, 49 Why plants change their names, 49 Taxonomic changes, 49 Nomenclatural changes, 50 Misidentification, 50 The quest for stability and linking information systems, 50 Botanical plant name stability, 51 Cultivated plant name stability, 51 How to identify a plant, 52 Conclusion, 53 Further reading, 53 Authors and affiliations, 54 5 Selecting and breeding plants, 55 Summary, 55 Introduction: adaptation and design, 55 Genes, 56 Gene regulation, 58 Chromosomes, 59 DNA replication, 60 Genomes, 61 Gamete formation, 61 Recombination, 62 Allelic variation, 62 Mutation, 62 Transposons, 62 Somatic and germ line mutations, 64 Chimeras, 64 Heterozygosity and homozygosity, 67 Dominant and recessive alleles, 67 Breeding systems, 68 Breeding inbred lines, 69 Breeding open-pollinated populations, 69 Clonal propagation, 70 F1 hybrid breeding, 70 Wide hybridisation, 71 Somatic variation, 71 Somatic hybridisation, 71 Recombinant DNA technology, 72 Marker-assisted breeding, 72 Genome sequencing, 72 Genetic modification, 73 Conclusion, 74 Further reading, 74 Authors and affiliations, 74 6 Summary, 75 Introduction, 75 Why do plants need soil?, 75 What do plants want from the soil?, 75 How soils are formed, 75 Physical properties of soils, 76 Chemical properties of soils, 79 Biological properties of soils, 80 Roots and soils, 82 Conclusion, 85 Further reading, 85 Authors and affiliations, 85 7 Soil cultivation and fertility, 86 Summary, 86 Cultivating the soil, 86 Managing soil nutrients, 88 Sources of the major plant nutrients, 89 Fertilisers, 91 Manures, 93 Composts, 93 Managing soil pH, 94 Managing water, 96 Soil-less growing media, 98 Conclusion, 101 Further reading, 101 Authors and affiliations, 101 8 The plant environment: Light and water, 102 Summary, 102 Introduction, 102 Light and photosynthesis, 102 The measurement of light, 103 Controlling gas exchange, 104 Effect of the environment on photosynthesis, 105 The effects of shade, 105 Water, 108 How water loss from the leaf is controlled, 109 The mechanisms of stomatal opening and closure, 109 Water stress, 109 The problem of drought, 110 Physical structures that help to conserve water, 111 Biochemical pathways that help conserve water, 113 C-4 plants, 113 Crassulacean acid metabolism, 114 Salinity, 115 Too much water, 115 Aquatic plants, 117 Watering in the garden, 117 Choosing plants for particular conditions, 117 Conclusion, 117 Further reading, 118 Authors and affiliations, 119 9 Plants and seasons, 120 Summary, 120 Introduction, 120 Day-length, 120 Mechanisms for the control of flowering by day-length, 124 Detection of day-length by the leaf, 127 Chemical nature of the flowering signal, 128 Plant hormones and flowering, 129 Formation of storage organs in response to day-length, 131 Day-length and the control of leaf-fall and dormancy, 133 Temperature, 134 Vernalisation, 135 The advantages of vernalisation for a plant, 136 Effective temperatures for vernalisation, 136 Devernalisation, 136 Direct effects of temperature on flowering, 136 Damage caused by sub-zero temperatures, 136 Breaking winter dormancy, 137 Increasing temperatures, 138 Conclusion, 138 Further reading, 138 Authors and affiliations, 138 10 Growing plants from seed, 139 Summary, 139 Introduction, 139 Seed production and germination, 139 Recalcitrant seeds, 140 Seed storage, 141 Dormancy, 142 Physiological dormancy, 142 Morphological dormancy, 142 Physical dormancy, 143 Germination, 144 Alternating temperatures and light, 144 Phytochrome, 145 Nitrate and smoke, 145 Some practical considerations, 146 Collecting seeds, and F1 hybrids, 147 Further reading, 148 Authors and affiliations, 148 11 Vegetative propagation, 149 Summary, 149 Introduction, 149 Characteristics of vegetative propagation and its value to gardeners, 149 How plants regenerate, 150 Practical propagation, 154 Softwood cuttings, 154 Hardwood cuttings, 156 Evergreen cuttings, 157 Leaf cuttings, 157 Root cuttings, 158 Layering, 159 Division, 160 Other organs, 161 Grafting and budding, 161 Micropropagation, 163 Conclusion, 164 Further reading, 165 Authors and affiliations, 165 12 Size and form, 166 Summary, 166 Introduction, 166 How size is controlled, 166 Endogenous factors, 166 External factors controlling size, 167 How form is controlled, 168 External factors, 168 Form and size can be manipulated by the gardener, 169 Pruning, 169 Special training methods, 170 Special forms, 171 Conclusions, 173 Further reading, 173 Authors and affiliations, 174 13 Colour, scent and sound in the garden, 175 Summary, 175 Introduction, 175 Colour in plants, 175 The perception of colour, 175 Plant pigments, 176 Pigments as attractants, 177 Variegation, 178 Chimeras, 178 Transposons, 178 Pattern genes, 178 Viruses, 178 Tulipomania, 179 Environmental factors influencing colour, 179 Seasonal changes, 180 The use of colour in the garden, 180 Scent and flavour, 181 Scent wheels, 184 Sound, 185 The nature, perception and appreciation of sound, 185 Sounds for pleasure, 186 Conclusion, 190 Further reading, 190 Authors and affiliations, 190 14 Climate and weather, 191 Summary, 191 Introduction, 191 Temperature, 192 Heat, 192 Cold, 193 Hardiness, 194 Growing season, 194 Soil temperature, 196 Precipitation, 197 Impacts of rainfall, snow and hail, 197 Seasonality of precipitation, 197 Extremes of rainfall, 197 Humidity, 198 Wind, 198 Nature and causes, 199 Effects of wind, 199 Pressure, 199 Light, 200 Day-length, 200 Angle of the sun, 200 Light intensity, 201 Sunshine hours, 202 Seasonality, 202 Climate, 203 Difference between climate and weather, 203 Global climatic zones, 204 UK climate influences, 204 Conclusion, 205 Further reading, 205 Authors and affiliations, 205 15 Climate and other environmental changes, 206 Summary, 206 Global environmental change, 206 Changes in atmospheric composition, 206 Climate change and climate variation, 208 Changes in nutrient cycles, 211 Other environmental changes, 212 Conclusions, 213 Further reading, 213 Authors and affiliations, 213 16 Protected cultivation, 214 Summary, 214 Why protect plants?, 214 What are the benefits?, 214 Temperature, 215 Development, 215 Stem growth, 216 Cold tolerance, 217 Principles of protection, 217 Energy transfer, 217 The importance of light, 217 Cladding materials, 218 Glass, 218 Film plastics, 218 Bubble plastic sheets, 219 Polycarbonate sheets, 219 Types of protection, 219 Mulches, 219 Horticultural fleeces and meshes, 219 Cloches and cold frames, 219 Tunnels, 220 Greenhouses, 220 Systems to be added, 222 Heating systems, 222 Ventilation, 222 Energy saving, 222 Carbon dioxide (CO2), 223 Lighting, 224 Irrigation, 224 Control systems, 225 Biological control, 225 Mechanisation, 225 Special cases, 225 Plant growth regulators, 226 Does protection have disadvantages?, 226 Crops grown under protection, 227 Chrysanthemum, 227 Cucumber, 228 Lettuce, leafy salads and other salad vegetables, 229 Poinsettia, 229 Strawberry, 230 Tomato, 231 Pot plants, 233 Conclusions, 233 Further reading, 233 Authors and affiliations, 233 17 The diversity of the undesirables, 234 Summary, 234 Introduction, 234 Pests, 234 Nematodes (eelworms), 234 Molluscs: slugs and snails, 234 Mites, 234 Insects, 234 Birds and mammals, 235 Diseases, 235 Opportunists, 237 Necrotrophs: destructive parasites, 237 Biotrophs: non-destructive parasites, 237 Hemibiotrophs, 237 Symptoms caused by the different types of pathogenic microorganisms, 237 Weeds, 239 Annual weeds, 239 Perennial weeds, 239 Weed origins, 239 Useful weeds, 240 Intraspecific diversity, 241 New pests and diseases, 242 Deciding whether an organism is a problem, 243 When is a pest a pest?, 243 The importance of weather, 244 When to control pests, 244 When is a disease a problem?, 244 Weed problems, 245 Poisonous and irritant plants, 246 Conclusion, 247 Further reading, 247 Authors and affiliations, 247 18 Controlling the undesirables, 248 Summary, 248 Introduction, 248 Keeping out the undesirables, 248 The role of the UK government, 248 The role of the horticultural industry, 249 The role of gardeners, 250 Know your enemy, 252 Control, 253 Cultural practices ('good gardening'), 253 Physical methods, 255 Host resistance or tolerance, 256 Biological control, 257 Chemical control, 259 Conclusions, 261 Further reading and sources of information, 261 Books, 261 Websites, 261 Authors and affiliations, 261 19 Maturation, ripening and storage, 262 Summary, 262 Introduction, 262 Changes in metabolism and ethylene synthesis, 262 Respiration and water loss, 262 Ethylene, 263 Maturation and ripening, 264 Seeds, 264 Fruits, 265 Vegetables, 265 Cut flowers, 266 Pre-harvest influences on storage quality, 266 Diseases and disorders, 266 Climatic factors, 267 Field factors, 268 Varietal factors, 268 Harvesting, handling and preparation for storage, 269 Time of harvest, 269 Handling, 269 Post-harvest treatments, 270 The storage environment, 271 Fresh produce, 271 Low-temperature storage methods, 271 Controlled atmosphere (CA) storage, 272 Seeds, 273 Trends in commercial storage, 274 Non-commercial storage, 275 Seeds, 275 Soft fruits, 275 Stone fruits, 275 Pome fruits, 275 Vegetables, 276 Cut flowers, 276 Conclusion, 276 Further reading, 276 Authors and affiliations, 277 20 Garden ecology, 278 Summary, 278 Ecology and ecosystems, 278 Ecology: open and closed systems, 278 Food webs, 278 Nutrient and carbon cycling, 279 Cycling at the global scale, 280 Habitats, 282 Climate and soil tolerance, 282 Natural processes and human land management, 283 Slow-growing and fast-growing plants, 284 Competition and herbivory, 286 Habitat creation, 286 Biodiversity, 288 Why are there so many plants?, 288 Diversity and stability, 289 Ecological succession and the balance of nature, 289 Unstable dynamics, 290 Conclusions, 290 Further reading, 291 Authors and affiliations, 291 21 Garden wildlife and conservation, 292 Summary, 292 Natives and aliens, 292 Gardens and native flora, 292 Native species and the Southwood hypothesis, 293 Invasive plants and animals, 294 Gardens and the wider environment, 295 Wildlife in gardens, 295 Ecosystem services, 296 Conservation in gardens, 296 Conservation of wild plants, 296 Conservation of cultivars, 297 Conclusions, 298 Websites and further reading, 298 Websites, 298 Books, 298 Authors and affiliations, 298 22 Low-input and low-impact gardening, 299 Summary, 299 Introduction, 299 Conservation of resources in the garden, 299 Soil nutrients and organic matter, 299 Water management, 300 Recycling other materials, 302 Wildlife, 302 Carbon and greenhouse gas emissions, 304 The problem of peat, 305 Environmental footprint of lawns, 305 Cash benefit of low-intensity garden management, 306 Conclusions, 306 Further reading, 306 Websites, 306 Books, 306 Authors and affiliations, 306 23 Health, well-being and socio-cultural benefits, 307 Summary, 307 Gardens and ecosystem service provision, 307 Why garden?, 307 Gardens and green therapy, 309 Restorative landscapes, 313 Horticultural therapy, 314 Health risks, 315 Crime and antisocial behaviour, 316 Social and educational opportunities, 316 Children and green space, 317 Encouraging a balanced diet, 317 Gardening and attitudes to the wider environment, 318 Conclusions, 319 Further reading, 319 Author and affiliations, 319 24 Gardens for science, 320 Summary, 320 Introduction, 320 Botanic gardens, 320 European origins and development in the United Kingdom, 320 Collections, 322 Research, 324 Conservation, education and training, 325 The gardens of horticultural societies, 325 Private and small commercial gardens, 325 Universities and independent research institutes, 326 Conclusion, 328 Further reading, 328 Authors and affiliations, 328 Glossary, 329 Index, 355