Intercellular Communication in Plants: Studies on Plasmodesmata

This Volume attempts to summarise and integrate a field of study in its entirety: the nature of plasmodesmata, and the part these inter­ cellular connections play in the life of the plant. Except in the all­ embracing early reviews of the pre-electron microscope era, there has been a tendency for the subject to be approached from disparate points of view: plant physiologists, developmental biologists, biophysicists, virologists and cytologists all contributing to the corpus of knowledge, but often without a full appreciation of each others' goals and probl­ ems, and sometimes misinterpreting each others' findings. In June 1975 a group of about 40 specialists in these various disciplines, all with a common interest in intercellular communication in plants, met for two days, presented papers, talked, argued, and in general pooled their know­ ledge. Out of a synthesis of manuscripts and discussions there has emerged, by an editorial process of elimination of unnecessary dupli­ cation and insertions to ensure completeness of coverage, the present book - not so much a straight record of a conference, as a Monograph based on the proceedings. All of the Chapters are reviews and most include hitherto unpublished data or theoretical treatments.

1 Introduction to Plasmodesmata.- 1.1. Introduction to Plasmodesmata.- 1.2. Analogues of Plasmodesmata.- 1.2.1. The Hydrodynamics of Micropores: Theory.- 1.2.2. The Hydrodynamics of Micropores: Practice.- 1.2.3. Qualitatively Analogous Structures in Animals.- 1.3. Conclusion.- 1.4. Open Discussion.- 2 Plasmodesmata in Higher Plants.- 2.1. Introduction.- 2.2. What are Plasmodesmata?.- 2.3. Distribution and Frequency.- 2.3.1. Distribution in Higher Plants.- 2.3.2. Frequencies between Cells.- 2.4. Structure.- 2.4.1. Optical Microscopy.- 2.4.2. Electron Microscopy.- 2.4.3. Variation in Structure.- 2.4.4. Plasmodesmata in Phloem.- 2.5. Some Concepts of Plasmodesmatal Function.- 2.6. Open Discussion.- 3 Plasmodesmata in Algae and Fungi.- 3.1. Introduction.- 3.2. Cyanophyta.- 3.3. Rhodophyta.- 3.4. Phaeophyta.- 3.4.1. Filamentous and Pseudoparenchymatous Thalli.- 3.4.2. Parenchymatous Thalli.- 3.5. Chlorophyta.- 3.6. Fungi.- 3.7. Conclusions.- 3.8. Open Discussion.- 4 The Origin and Development of Plasmodesmata.- 4.1. Introduction.- 4.2. Primary Formation of Plasmodesmata.- 4.2.1. Formation of Plasmodesmata during Cytokinesis that is Coupled to Nuclear Division.- 4.2.2. Formation of Plasmodesmata during Cell Wall Formation that is Independent of Nuclear Division.- 4.3. Secondary Formation of Plasmodesmata.- 4.3.1. Fusion of Like Cells.- 4.3.2. Fusion of Unlike Cells.- 4.3.3. Perforation of Existing Walls.- 4.3.4. Branched Plasmodesmata.- 4.3.5. Mechanism of Secondary Formation of Plasmodesmata.- 4.4. Distribution of Plasmodesmata.- 4.5. Control of Frequency and Distribution of Plasmodesmata.- 4.6. Structural Modifications of Plasmodesmata.- 4.7. Mechanisms of Structural Modification.- 4.8. Conclusions.- 4.9. Open Discussion.- 5 Physico-Chemical Assessment of Plasmodesmatal Transport.- 5.1. Introduction.- 5.2. Irreversible Thermodynamic Formulation.- 5.3. Treatment by Tyree.- 5.4. Reassessment of Solute Permeability.- 5.5. Plasmodesmatal Electrical Resistances.- 5.6. Summary.- 5.7. Appendix.- 5.8. Open Discussion.- 6 Physiological and Electrophysiological Evidence for Intercellular Communication in Plant Symplasts.- 6.1. Introduction.- 6.2. Intercellular Movement of Compounds in a Tissue Compartment Isolated from External Solutions.- 6.3. Intercellular Propagation of Action Potentials.- 6.4. Direct Evidence for the Electrical Coupling of Plant Cells.- 6.5. Intercellular Movement of Injected Chemicals.- 6.6. Discussion.- 6.7. Open Discussion.- 7 Cytochemical Evidence for Ion Transport Through Plasmodesmata.- 7.1. Introduction.- 7.2. Materials and Methods.- 7.2.1. Ion Localisation.- 7.2.2. X-Ray Analysis.- 7.2.3. Adenosine Triphosphatase Localisation.- 7.3. Results.- 7.3.1. Ion Localisation.- 7.3.2. Ion Precipitation using Antimonate.- 7.3.3. Adenosine Triphosphatase1.- 7.4. Discussion.- 7.5. Summary.- 7.6. Open Discussion.- 8 Viruses and Plasmodesmata.- 8.1. Movement of Viruses in Plants.- 8.2. Sizes of Virus Particles and Genomes.- 8.3. Plasmodesmata in Virus-Infected Plants.- 8.3.1. Viruses with Filamentous or Tubular Particles.- 8.3.2. Viruses with Isometric Particles.- 8.3.3. Viruses with Bacilliform Particles.- 8.4. Ectodesmata, Plasmodesmata and Virus Infection.- 8.5. Virus Nomenclature.- 8.6. Open Discussion.- 9 Transport of Solutes Through the Plasmodesmata of Chara Nodes.- 9.1. Introduction.- 9.2. Symbols Used.- 9.3. Theoretical.- 9.3.1. Rate-of-Arrival.- 9.3.2. The Counter-Current Node.- 9.3.3. The Co-Current Node.- 9.4. The Real Chara Node.- 9.5. Experimental Evidence.- 9.6. Discussion and Conclusions.- 9.7. Open Discussion.- 10 The Role of Plasmodesmata in the Transport of Water and Nutrients Across Roots.- 10.1. Introduction.- 10.2. The Plasmodesmata of Roots.- 10.2.1. Structure.- 10.2.2. Distribution.- 10.3. The Symplastic Compartment.- 10.4. The Root Endodermis.- 10.5. The Movement of Water and Ions Across the Root.- 10.5.1. Some Published Assessments.- 10.5.2. Water.- 10.5.3. Phosphate and Potassium.- 10.5.4. Relevance of Cytochemical Studies to the Function of Root Plasmodesmata.- 10.5.5. Bidirectional Movement Through Plasmodesmata.- 10.5.6. Passage Cells.- 10.6. Movement of Water and Ions Into the Xylem.- 10.7. Conclusions.- 10.8. Open Discussion.- 11 The Role of Plasmodesmata in Short Distance Transport to and from the Phloem.- 11.1. Introduction.- 11.2. Symplastic Pathways Between Donor Tissues and Sieve Elements.- 11.2.1. The Leaf Mesophyll.- 11.2.2. The Vein Boundary.- 11.2.3. The Phloem.- 11.2.4. Loading Fluxes and Pathways.- 11.3. Unloading the Phloem.- 11.4. Open Discussion.- 12 Symplastic Transport of Metabolites During C4-Photosynthesis.- 12.1. Introduction.- 12.2. Compartmentation in C4 Photosynthesis.- 12.3. Structural Aspects.- 12.4. The Symplast Flux During C4 Photosynthesis.- 12.5. The ‘CO2 Concentrating Mechanism’: Functional Aspects of Symplastic Transport in C4 Photosynthesis.- 12.6. Assessment.- 12.7. Open Discussion.- 13 Plasmodesmata in Growth and Development.- 13.1. Hypotheses and Assumptions.- 13.2. Cell Communication in Animals.- 13.3. Exchanges of Specific Information Between Plant Cells.- 13.3.1. A Nuclear Influence on Cell Wall Synthesis.- 13.3.2. Metabolic Co-operation.- 13.3.3. The Transport of Hormones.- 13.3.4. Conduction of Stimuli.- 13.4. Developmental Consequences of Isolation of Cells from Tissues.- 13.4.1. Consequences of Isolation Induced Plasmolytically or Mechanically.- 13.4.2. Plasmodesmata and Cell Differentiation.- 13.4.3. Plasmodesmata and Differentiation in Tissue Cultures.- 13.4.4. Isolation in the Development of Alternating Generations and during Reproduction.- 13.4.5. Adventitious Buds, Lateral Roots and Embryoids.- 13.5. Plasmodesmata in Cell Wall Growth.- 13.6. Dormancy.- 13.7. Plasmodesmata in Ageing and Longevity.- 13.8. Abscission.- 13.9. Parasites.- 13.9.1. Cuscuta.- 13.9.2. Visoum.- 13.9.3. Orobanohe.- 13.9.4. Avceuthobium.- 13.9.5. Phytophysa tveubii.- 13.9.6. Physiological Implications of Host-Parasite Relations.- 13.10. Plasmodesmata and the Regulation of Growth and Development.- 13.11. Open Discussion.- 14 Historical Perspectives on Plasmodesmata.- 14.1. Discovery and Exploration.- 14.2. Eclipse ― The Tyranny of Free Space.- 14.3. Rediscovery and Revival of Interest.- 15 Plasmodesmata: Current Knowledge and Outstanding Problems.- Author Index.