1 Xylem and Phloem Differentiation in Perspective.- 1.1 Introduction.- 1.2 Procambium Initiation in Embryos.- 1.3 General Mechanisms of Programming.- 1.4 Quiescent Center.- 1.5 Quantal Mitosis and Differentiation.- 1.6 Multiple Gene Copies and Xylogenesis.- 1.7 Procambium to Cambium.- 1.8 Maintenance and Extension of the Vascular System.- 2 Hormonal Aspects of Vascular Differentiation.- 2.1 Some Characteristics of Plant Hormones.- 2.2 Auxins.- 2.3 Cytokinins.- 2.4 Gibberellins.- 2.5 Ethylene.- 2.6 Polyamines.- 2.7 Inhibitors.- 2.8 Summary.- 3 Vascular Differentiation Within the Plant.- 3.1 Major Problems.- 3.1.1 In Vivo Versus In Vitro Systems.- 3.1.2 The Difficulty of Observing the Phloem.- 3.1.3 Primary Phloem Structure and the Zero-Day Control.- 3.2 Control of Vascular Differentiation by Auxin Flow.- 3.3 Role of Cytokinin in Vascular Differentiation.- 3.4 Relation Between Phloem and Xylem Differentiation.- 3.5 Graniferous Tracheary Elements.- 3.6 Control of Conduit Size and Density.- 3.7 Sites of Xylem Initiation and Rates of Maturation in Relation to Conduction.- 3.8 Role of Gibberellin and the Control of Fiber Differentiation...- 3.9 Transfer Cells.- 3.10 Vascular Adaptation.- 4 Evidence from Wound Responses and Tissue Cultures.- 4.1 Rationale for Using Wounds and Tissue Cultures to Study Vascular Differentiation.- 4.2 Coleus Stem Wounds and Cultured Internodal Explants.- 4.3 Root and Shoot Wounds of Pisum.- 4.4 Vascular Differentiation in Other Wound Systems.- 4.5 Induced Xylogenesis in Lactuca Pith Parenchyma.- 4.6 Xylogenesis in Explants from Storage Organs.- 4.7 Differentiation in Suspension Cultures Including the Zinnia System.- 4.8 Cell Wall Metabolism During Xylem Differentiation.- 4.9 Some Final Thoughts on Tissue Culture Systems.- 5 Physical Factors, Hormones, and Differentiation.- 5.1 Identification of the Physical Factors Influencing Vascular Differentiation.- 5.2 Temperature.- 5.3 Water.- 5.4 Light.- 5.5 Gases.- 5.6 Mechanical Stress.- 5.7 Acidity.- Epilogue.- References.- Appendix: Abbreviations.
