Plant Roots: Growth, Activity and Interactions with the Soil

1. Plants, Roots and the Soil.

1.1 The evolution of roots.

1.2 Functional interdependence of roots and shoots.

1.2.1 Balanced growth of roots and shoots.

1.2.2 Communication between roots and shoots.

1.3 Roots and the soil.

1.3.1 The root-soil interface.

1.3.2 Root-induced soil processes..

2. Roots and the Architecture of Root Systems.

2.1 Nomenclature and types of root.

2.2 Root structure.

2.2.1 Primary structure.

2.2.2 Secondary structure.

2.3 Extension and branching.

2.3.1 Extension.

2.3.2 Branching.

2.3.3 Root hairs.

2.4 The root tip.

2.4.1 The root cap and border cells.

2.4.2 Mucilage.

2.5 Architecture of root systems..

3. Development and Growth of Root Systems.

3.1 Measurement of root systems.

3.1.1 Washed soil cores.

3.1.2 Rhizotrons and minirhizotrons.

3.1.3 Other techniques.

3.2 Root system development.

3.3 Size and distribution of root systems.

3.3.1 Mass and length.

3.3.2 Depth of rooting.

3.3.3 Distribution of roots.

3.4 Root:shoot allocation of dry matter.

3.5 Root longevity and turnover.

3.6 Modelling of root systems..

4. The Functioning Root System.

4.1 Root anchorage.

4.1.1 Uprooting.

4.1.2 Overturning.

4.2 Water uptake.

4.2.1 The concept of water potential.

4.2.2 The soil-plant-atmosphere continuum.

4.2.3 Water uptake by plant root systems.

4.3 Nutrient uptake.

4.3.1 Nutrient requirements of plants and the availability of nutrients.

4.3.2 Nutrient movement in soil solution.

4.3.3 Nutrient uptake and movement across the root.

4.3.4 Nutrient uptake by root systems..

5. Roots and the Physico-Chemical Environment.

5.1 Temperature.

5.1.1 Root development and growth.

5.1.2 Root orientation.

5.1.3 Other root functions.

5.2 Gravity and other tropistic responses.

5.2.1 Gravisensing and the response of roots.

5.2.2 Phototropism, hydrotropism and thigmotropism.

5.3 Soil mechanical properties.

5.3.1 Root elongation and mechanical impedance.

5.3.2 Root responses to mechanical impedance.

5.3.3 Roots and soil structure.

5.4 Soil pores and their contents.

5.4.1 Soil water.

5.4.2 Soil aeration.

5.4.3 Waterlogging and aerenchyma.

5.5 The soil chemical environment.

5.5.1 Plant nutrients.

5.5.2 Low pH and aluminium.

5.5.3 Salinity.

5.6 Atmospheric CO2 concentration..

6. Roots and the Biological Environment.

6.1 Interactions of roots with soil organisms.

6.1.1 Root-rhizosphere communication.

6.1.2 Interactions with bacteria.

6.1.3 Interactions with fungi.

6.1.4 Interactions with protozoa.

6.1.5 Interactions with nematodes and mesofauna.

6.2 Symbiotic associations.

6.2.1 Rhizobia and N fixation.

6.2.2 Mycorrhizas.

6.3 Root pathogens and parasitic associations.

6.3.1 Fungal diseases.

6.3.2 Nematodes.

6.3.3 Parasitic weeds.

6.4 Root herbivory by insects..

7. The Rhizosphere and Root Modification of Soils.

7.1 Rhizodeposition.

7.1.1 Quantities of rhizodeposits.

7.1.2 Composition of rhizodeposits.

7.1.3 Nitrogen rhizodeposits.

7.2 Chemical changes affecting nutrient acquisition.

7.2.1 Rhizosolution composition and replenishment.

7.2.2 Changes in pH.

7.2.3 Changes in redox conditions.

7.2.4 Root exudates and phytosiderophores.

7.2.5 Enzyme activity.

7.3 Physical changes in the rhizosphere.

7.3.1 Bulk density and porosity.

7.3.2 Water..

8. Genetic Control of Root System Properties.

8.1 Genotypic differences in root systems.

8.1.1 Size and architecture.

8.1.2 Functional properties.

8.2 Genetics of root systems.

8.2.1 Genetic control of root development and growth.

8.2.2 Genetic control of root properties.

8.3 Breeding better root systems.

8.3.1 Use of markers and QTL..

9. Root Systems as Management Tools.

9.1 Optimal root systems and competition for resources.

9.2 Intercropping and agroforestry.

9.3 Crop rotations.

9.3.1 Biological drilling.

9.3.2 Utilization of subsoil water.

9.3.3 Allelopathy.

9.3.4 Biofumigation by brassicas.

9.4 Phytoremediation.

Index.