Transport in Plants II

In the first part (Part A) of this volume on transport, there was an emphasis on the processes occurring at the membranes bounding the cells. It was convenient to distinguish active and passive processes of transport across the membranes, and to recognize that certain transport processes may be regulated by internal factors in the cells such as cytoplasmic pH, concentrations of ions, of malate or of sugar in the vacuoles, or the hydrostatic pressure. Cells in tissues and organs show the same kinds of properties as individual cells, but in addition there can be cell to cell transport related to the organization of the tissue. Firstly cells within a tissue are separated from the external solutions by a diffusion path comprising parts of the cell walls and intercellular spaces; more generally this extra-cytoplasmic part of the tissue has been called the apoplasm. A similar term is "free space". Secondly, the anatomy of cells in tissues seems to allow some facilitated, local transport between cells in a symplasm. Entry into the symplast and subsequent transport in a symplasmic continuum seems to be privileged, in that ions may not have to mix with the bulk of the cytoplasm and can pass from cell to cell in particular cytoplasmic structures, plasmodesmata. In Chara plants, this kind of transport is found operating across the multi-cellular nodes as the main means of transport between the long internodal cells.

Contenu

of Part B.- I. Pathways of Transport in Tissues.- 1. Apoplasmic Transport in Tissues.- 1. Introduction.- 2. Chemical and Cytological Properties of the Cell Wall in Relation to Apoplasmic Transport.- 3. Cytological and Chemical Properties of Cuticles in Relation to Apoplasmic Transport.- 4. Apoplasmic Transport in Tissues.- 5. Conclusions.- 2. Symplasmic Transport in Tissues.- 1. Introduction.- 2. The Ultrastructure of Plasmodesmata.- 3. The Formation and Occurrence of Plasmodesmata.- 4. Boundaries of Symplasmic Compartments in Plant Tissues.- 5. Symplasmic Transport.- 6. Conclusions.- II. Particular Tissue Systems.- 3. Transport Processes in Roots.- 3.1 General Introduction.- 1. Introduction.- 2. General Features of Roots.- 3. Conclusion.- 4. Appendix: Culture Solutions.- 3.2 Kinetics of Ion Transport and the Carrier Concept.- 1. Introduction.- 2. The Enzyme-Kinetic Formulation.- 3. The Dual Pattern of Ion Transport.- 4. Interpretations of the Experiments on Ion Absorption Kinetics.- 3.3 Ion Uptake by Plant Roots.- 1. Processes Involved in Ion Uptake.- 2. Electrical Measurements.- 3. Flux Measurements Using Roots.- 4. Ion Content of Plant Roots.- 5. Mechanisms of Divalent Cation Absorption.- 6. Mechanisms of Anion Absorption.- 7. Measurement of Absorption by the Root.- 8. Control of Absorption.- 9. Conclusions.- 3.4 Transport through Roots.- 1. Definition of Scope.- 2. Ion Transport.- 3. Water Transport.- 4. Transport of Organic Solutes.- 5. Summary of Transport Mechanisms.- 4. Transport Processes in Leaves.- 4.1 General Introduction.- 4.2 Ionic Relations of Leaf Cells.- 1. Introduction.- 2. Experimental Approaches.- 3. Results.- 3.1 Ion Concentrations and Electropotentials.- 3.2 Effect of Light on Ion Fluxes.- 3.3 Ion Fluxes, Effect of External Concentration.- 3.4 Energy Supply for Ion Fluxes.- 3.5 Effects of Light on the Membrane Potential and H+ Fluxes.- 4. Conclusions.- 4.3 Stomatal Ion Transport.- 1. Introduction.- 2. Early Work on Stomatal Ion Relations.- 3. Plant Material and Methodology.- 4. Evidence on the Osmotic Role of K+.- 5. Other Cations.- 6. Anions and Charge Balance.- 7. Starch and CO2.- 8. Sources of Energy.- 9. Stomatal Closure as Related to Opening.- 10. Path of Transport and Reversible Source-Sink Relationship.- 11. ABA and Phytochrome.- 12. Concluding Remarks.- 5. Elimination Processes by Glands.- 5.1 General Introduction.- 5.2 Mineral Ions.- 1. Introduction.- 2. Salt Glands.- 3. Salt Hairs.- 4. Secretory Glands of Carnivorous Plants.- 5.3 Organic Substances.- 1. Carbohydrates.- 1.1 Mechanisms of Membrane Transport of Sugars in Eucaryotic Plant Cells.- 1.2 Elimination of Sugars.- 1.3 Elimination of Polysaccharides.- 2. Elimination of Proteins.- 3. Elimination of Secondary Plant Products.- 6. Transport in Symbiotic Systems Fixing Nitrogen.- 1. Introduction.- 2. Morphological, Anatomical and Ultrastructural Attributes of the Symbioses.- 3. General Requirements for Transport between Participants.- 4. Transport in Symbioses Involving Blue-Green Algae.- 5. Transport in Symbioses Involving Rhizobium or an Actinomycete.- 6. Concluding Remarks.- III. Control and Regulation of Transport in Tissues and Integration in Whole Plants.- 7. Effect of Hormones and Related Substances on Ion Transport.- 1. Introduction.- 2. Auxins.- 3. Kinins.- 4. Gibberellins.- 5. Abscisic Acid (ABA).- 6. Senescence Factor (SF), C2H4 and CO2.- 7. Phytochrome, Cyclic AMP, Sterols, Phytotoxins, Polylysins, Iono-phores, etc.- 8. Hormonal Function and Ion Transport.- 9. Concluding Remarks.- 8. Cellular Differentiation, Ageing and Ion Transport.- 1. Introduction.- 2. Adaptation in situ.- 3. Induced Adaptation.- 4. Senescence in situ.- 5. Induced Senescence.- 6. Conclusion.- 9. Genotypic Variation in Transport.- 1. Introduction.- 2. Ecotypes-Their Adaption to Nutritional Factors.- 3. Genetic Control of Transport.- 4. Conclusions.- 10. Regulation in the Whole Plant.- 1. Introduction.- 2. Ion Distribution and Transpiration.- 3. Ion Distribution and Plant Development.- 4. Ion Distribution in Germinating Seeds.- 5. Hormonal Control of Redistribution.- 6. Regulation of Ion Transport-A Working Hypothesis.- Epilog: Integration of Transport in the Whole Plant.- Author Index (Part B).- Symbols, Units and Abbreviations.- Subject Index (Part A and B) (after p. 456).