Ontogeny, Cell Differentiation, and Structure of Vascular Plants

With improved microscope and preparation techniques, studies of histo- logical structures of plant organisms experienced a revival of interest at the end of the 19th century. From that time, histological data have sub- stantially studies of the pioneers in botanical science. From the beginning of the 20th century, the microscope allowed research in cell structure, the general functional unit of living beings. Advances in cytology gradually influenced histology, at first, however, rather timidly. Only the new and spectacular progress in ultrastructural cytology and cytochemistry led to a great increase in modern work on the structures of vascular plants and the related ontogenical and physiological data, thanks to the use of the electron microscope and the contribution of molecular biology. Not only did new techniques lead to new approaches, but achieve- ments in general biology shifted the orientation of research, linking in- vestigation to the physiological aspects of cell and tissue differentiation. Among these, the demonstration of the general principles of develop- ment, and the characterization of molecules common to plants and animals, which control and govern the main basic functions of cells and tissues, have widened the scope of modern research on plant struc- tures. Present trends in biological research show that it is necessary to know the structures thoroughly, from the ultrastructural cytological scale to the scale of tissue and organ arrangement, even for physiological research on either cells, tissues, or whole organs. The study of growth factors, differ- entiation, or organogenesis can be mentioned as an example.

Table of Contents:
1 Growth and Tissues.- 2 General Characteristics of Vascular Plants.- 3 Succinct Classification of Vascular Plants.- 4 The Two Phases of Sporophyte Development.- I Embryogeny and Post-embryonic Ontogeny.- 1 Segmentation and First Edification of the Sporophyte.- 1.1 Embryogeny in Atmospheric Medium.- 1.1.1 The Environment of the Zygote.- 1.1.1.1 The Prothallus is Free.- 1.1.1.2 The Prothallus is Enclosed.- The Prothallus is Acrescent.- The Prothallus is Resorbed.- 1.1.2 The Regularity of the Segmentation.- 1.1.3 Seed Plants and Plants Without Seeds.- 1.2 Embryogeny of Pteridophytes.- 1.2.1 Early Segmentations of the Zygote.- 1.2.2 Embryogeny of Psilotales.- 1.2.3 Embryogeny of Lycopodineae.- 1.2.3.1 Aliguleae (Lycopodium-Phylloglossum).- Type Lycopodium selago.- Type Lycopodium clavatum.- Type Lycopodium cernuum.- 1.2.3.2 Liguleae.- Genus Selaginella.- Genus Isoetes.- 1.2.4 Embryogeny of Equisetales.- 1.2.5 Embryogeny of Ferns.- 1.2.5.1 Eusporangiate Ferns.- 1.2.5.2 Leptosporangiate Ferns.- 1.2.6 Conclusions.- 1.3 Embryogeny of Prephanerogams.- 1.3.1 Embryogeny of Cycadales.- 1.3.2 Embryogeny of Ginkgoales.- 1.3.3 Conclusions.- 1.4 Embryogeny of Gymnosperms.- 1.4.1 The Formation of the Proembryo.- 1.4.2 The Formation of the Suspensor and the Embryo.- 1.4.3 Conclusions.- 1.5 Embryogeny of Preangiosperms.- 1.5.1 Fertilization in Gnetales.- 1.5.2 Embryogeny of Ephedra.- 1.5.3 Embryogeny of Welwitschia.- 1.5.4 Embryogeny of Gnetum.- 1.5.5 Conclusions.- 1.6 Embryogeny of Angiosperms.- 1.6.1 The Proembryo.- 1.6.1.1 Edification of the Proembryo of Myosurus minimus (Soueges, 1911).- 1.6.1.2 Variants and Their Signification.- 1.6.2 The Embryo.- 1.6.2.1 Dicotyledons:.- Edification of the Embryo of Myosurus minimus.- 1.6.2.2 Monocotyledons:.- Edification of the Embryo of Sagittaria sagittaefolia.- 1.6.2.3 Significance of the "Cotyledon" of the Monocotyledons.- 1.6.3 Some Cytological Data on the Embryogeny of Angiosperms.- 1.6.3.1 The Zygote.- 1.6.3.2 The Suspensor.- 1.6.3.3 The Embryo.- 1.6.3.4 The Plantlet in the Mature Seed.- 1.7 General Considerations on the Embryogeny of Vascular Plants.- 1.7.1 The Geometry of Segmentation and its Results.- 1.7.2 Predestination or Epigenesis.- 1.7.3 Segmentation and Organogenesis.- 1.7.4 Formation of Organogenic Cells, Cytological Results of Embryogenesis.- 1.7.5 Dedifferentiation at the Origin of Ontogenesis.- 1.7.6 The Embryonic Differentiation.- References.- 2 Meristems and the Indefinite Ontogeny of Plants.- 2.1 Apical Meristems.- 2.1.1 Ontogenetic Function of Apical Meristems.- 2.1.2 Histological Structure of Shoot Apical Meristems.- 2.1.2.1 Successive Concepts.- The "Apical Cell", Single Initial.- The Histogens.- Schmidt's Interpretation.- The Initiating Ring (Anneau Initial) and the Critic of the Apical Initiation.- 2.1.2.2 Shoot Apical Meristems of Pteridophytes.- Advanced Pteridophytes.- Primitive Pteridophytes.- 2.1.2.3 Apical Meristems of Prephanerogams (Prespermaphytes).- 2.1.2.4 Apical Meristems of Gymnosperms.- 2.1.2.5 Apical Meristems of Angiosperms.- 2.1.3 Histological Structure of Root Meristems.- 2.1.3.1 Pteridophytes.- 2.1.3.2 Phanerogams.- 2.1.4 Cytological Structure of Apical Meristems.- 2.1.4.1 Primary Meristematic Cells.- 2.1.4.2 Rib (Medullary) Meristem Cells.- 2.1.5 Functioning of Shoot Apical Meristems.- 2.1.6 Organization of the Primary Structure of the Leafy Stem.- 2.1.6.1 Initiation of Leaves.- 2.1.6.2 Formation of Leaf Buttresses.- 2.1.6.3 Evolution of the Leaf Base.- 2.1.6.4 The Two Ontogenic Composing Parts of the Stem.- 2.1.6.5 The Organization of Leaf Segments.- 2.1.6.6 Components of the "Primary Structure".- 2.1.7 Establishment of the Primary Structure of the Root.- 2.2 Secondary Meristems.- 2.2.1 Origin and Function of Secondary Meristems.- 2.2.2 The "Prodesmogen" and the Vascular Cambium.- 2.2.3 The Phellogen (Cork Cambium).- 2.2.3.1 The First Phellogen Layer.- 2.2.3.2 Renewal of the Phellogen.- 2.2.4 The Cambium of Monocotyledons.- 2.2.5 Cytological Features of Secondary Meristems.- 2.2.6 Cytology and Meristematic Potentialities.- 2.2.7 Distribution of Secondary Meristems in Vascular Plants.- References.- 3 Cytology of the Processes of Differentiation and Dedifferentiation During the Ontogeny of Vascular Plants.- 3.1 The Plasticity of Plant Cells.- 3.2 General Cytological Scheme of Differentiation.- 3.2.1 Development of the Nucleus, the Cytoplasm and Vacuoles.- 3.2.2 Development of the Chondriome.- 3.2.3 Development of the Cell Wall.- 3.2.3.1 Relations Between Cytoplasm and Cell Wall.- 3.2.3.2 Heterogeneity of the Cell Wall Structure: Cell Wall Layers.- 3.2.3.3 Origin of the Cell Wall and the Middle Lamella.- 3.2.3.4 The Primary Cell Wall.- 3.2.3.5 The Secondary Cell Wall.- 3.2.3.6 Changes in the Secondary Cell Wall.- 3.3 The Course of the Differentiation.- 3.3.1 The First Phase.- 3.3.2 The Second Phase.- 3.4 The Main Types of Tissues.- 3.5 Processes of Dedifferentiation in the Course of Ontogeny.- 3.5.1 Circumstances of Dedifferentiation.- 3.5.2 The Phases of Dedifferentiation.- 3.5.3 Dedifferentiation and Mode of Growth.- References.- II Histological Differentiation of Vascular Plants.- 4 Parenchyma.- 4.1 General Characteristics.- 4.2 Main Types of Parenchyma.- 4.2.1 Assimilatory Parenchyma.- 4.2.2 Storage Parenchyma.- 4.3 Intercellular Relations and Morphology of Cells.- 4.4 Secondary Parenchyma.- 4.5 Parenchyma in the Series of Vascular Plants.- References.- 5 Protective Tissues.- A. Epidermis.- 5.1 Histological, Ontogenic and Chemical Characteristics.- 5.2 Epidermal Cells.- 5.2.1 Common Epidermal Cells.- 5.2.2 Stomatal Cells (Guard Cells).- 5.2.2.1 Cell Wall Differentiation of Stomatal Cells.- 5.2.2.2 Ontogenesis and Classification of Stomata.- 5.2.2.3 Ultrastructure of Stomatal Cells.- 5.2.2.4 Cytophysiology of Stomata.- 5.2.3 Trichomes.- 5.2.3.1 Protective Trichomes.- 5.2.3.2 Secretory or Glandular Trichomes.- 5.2.3.3 Development of Trichomes.- 5.2.4 Secretory Epidermis.- 5.2.5 Lithocysts.- 5.2.6 Other Types of Epidermal Cells.- 5.3 Multiseriate Epidermis.- 5.4 Cytophysiological Problems Related to the Differentiation of Epidermis.- 5.5 Epidermal Productions in Vascular Plants.- B. Cork (Phellem).- 5.6 Origin of Cork: Primary and Secondary Cork.- 5.7 Differentiation of Cork Cells.- 5.8 Primary Cork.- 5.9 Secondary Cork (Peridermal Cork).- 5.10 Storied Cork of Arborescent Monocotyledons.- 5.11 Lenticels.- References.- 6 Phloem.- 6.1 Characteristic Cell Element: The "Sieve Cell".- 6.1.1 Cell Wall Differentiations.- 6.1.2 The Contents of Sieve Cells.- 6.1.2.1 The Nucleus.- 6.1.2.2 Plastids and Mitochondria.- 6.1.2.3 The "Slime Bodies" or P-Proteins.- 6.1.2.4 Cytoplasm and Vacuoles.- 6.2 Relations Between Sieve Cells, and Between Sieve Cells and Adjacent Cells.- 6.2.1 Differentiation of Sieve Plates.- 6.2.2 Differentiation in Lateral Walls.- 6.3 Companion Cells.- 6.4 The Phloem Parenchyma.- 6.4.1 "Vertical" Phloem Parenchyma (Axial Parenchyma).- 6.4.2 "Horizontal" Phloem Parenchyma (Ray Parenchyma).- 6.4.3 Phloem Parenchyma Pits.- 6.4.4 Some Cytochemical Data.- 6.5 Phloem Fibres.- 6.6 Primary Phloem.- 6.6.1 Protophloem.- 6.6.2 Metaphloem.- 6.7 Secondary Phloem.- 6.7.1 Secondary Phloem of Gymnosperms.- 6.7.2 Secondary Phloem of Dicotyledons.- 6.7.2.1 Various Cell Types and Their Arrangement.- 6.7.2.2 The Sieve Cell in the Series of Dicotyledons.- 6.8 The Phloem in the Series of Vascular Plants.- 6.9 Histology and Cytology of the Phloem and Mechanisms of Translocation.- References.- 7 Xylem (Vascular Tissues).- 7.1 Characteristic Elements: Tracheids and Vessel Members.- 7.1.1 General Structures of the Cell Walls of Differentiated Tracheids and Vessel Members.- 7.1.2 Xylem Pits.- 7.1.3 Cell Wall Differentiation of Tracheids and Vessel Elements.- 7.1.3.1 Infrastructural Cytology of Secondary Cell Wall Elaborations: Transversal Growth, Dictyosomes, Endoplasmic Reticulum, Microtubules, Intercellular Connections.- 7.1.3.2 Cytology of Perforation Processes Between Vessel Elements.- 7.1.3.3 Partial Hydrolysis in Bordered Pits Between Vessels or Between Tracheids.- 7.1.3.4 Infrastructural Cytochemistry of the Lignification.- 7.1.4 Nucleus and Cytoplasm Degeneration.- 7.1.5 Tertiary Thickenings and "Warty Layer".- 7.2 Xylem Fibres.- 7.2.1 General Features and Various Categories.- 7.2.2 Cytological Data, Seasonal Variations and Life Duration.- 7.3 Xylem Parenchyma.- 7.3.1 Vertical Xylem Parenchyma.- 7.3.2 Horizontal Xylem Parenchyma (Xylem Rays).- 7.3.3 Cytology and Seasonal Behaviour of Xylem Parenchyma.- 7.3.3.1 Seasonal Parenchymatous Productions of the Cambium.- 7.3.3.2 Ultrastructural Cytology of the Differentiation of Xylem Parenchyma.- 7.3.4 Tyloses.- 7.4 Primary Xylem.- 7.4.1 Protoxylem.- 7.4.2 Metaxylem.- 7.5 Secondary Xylem.- 7.5.1 Distinctive Characters.- 7.5.2 General Features.- 7.5.3 Gymnosperm Wood.- 7.5.3.1 Tracheids.- 7.5.3.2 Vertical Parenchyma and Resin Ducts.- 7.5.3.3 Horizontal Parenchyma.- 7.5.4 Ligneous Dicotyledon Wood.- 7.5.4.1 Distribution and Size of Vessels.- 7.5.4.2 Distribution of the Vertical Parenchyma.- 7.5.4.3 Structure of the Xylem Rays.- 7.5.4.4 Disposition of Terminal Walls of Vertical Parenchyma Cells.- 7.5.5 Histology and Mechanical Properties of Woods.- 7.6 The Xylem and the Systematics of Vascular Plants.- 7.7 The Xylem and the Phylogenic Trends of Vascular Plants.- References.- 8 Supporting Tissues.- A. Collenchyma.- 8.1 Cytological Structures of the Differentiated Collenchyma Cells.- 8.1.1 Structure of the Cell Wall.- 8.1.2 The Protoplasma of Collocytes.- 8.2 Origin and Setting in Place of the Collenchyma.- 8.3 Differentiation of the Collocytes.- 8.4 Anatomical Localization.- 8.5 Mechanical Properties.- 8.6 Collenchyma in the Series of Vascular Plants.- B. Sclerenchyma.- 8.7 General Characteristics and Various Types.- 8.8 Sclerenchyma of "First Formation".- 8.8.1 Compact Sclerenchymatous Tissues.- 8.8.2 Sclereids.- 8.9 Origin and Differentiation of the Cells of First Formation Sclerenchyma.- 8.9.1 Differentiation of Compact Sclerenchyma.- 8.9.1.1 Differentiation of the Protoplasma.- 8.9.1.2 Differentiation of Cell Walls.- 8.9.2 Differentiation of Sclereids.- 8.10 Late Sclerenchyma or Sclerenchyma of "Second Formation".- 8.11 Mechanical Properties.- References.- 9 Secretory Cells and Secretory Tissues.- 9.1 Concept and Various Types.- 9.2 Secretory Epidermis.- 9.3 Secretory Trichomes.- 9.4 Nectaries.- 9.5 Hydathodes.- 9.6 Secretory Cavities.- 9.6.1 Schizogenous Cavities.- 9.6.2 Schizolysigenous Cavities.- 9.7 Secretory Canals.- 9.8 Sites of Synthesis, Transport and Cytological Mechanisms of Excretion.- 9.9 Isolated Secretory Cells.- 9.10 Tanniniferous Cells.- 9.11 Pseudolaticifers.- 9.11.1 Concept.- 9.11.2 Anatomical Distribution and Arrangements.- 9.11.3 Origin and Mode of Growth.- 9.11.4 Systematic Repartition.- 9.11.5 Infrastructures of Pseudolaticifers.- 9.11.5.1 Vacuolar Apparatus.- 9.11.5.2 Other Organelles.- 9.11.5.3 Secretion Grains and Latex.- 9.11.5.4 Mechanisms of Cell Wall Perforation.- 9.12 True Laticifers.- 9.12.1 Origin and Development.- 9.12.2 Differentiation and Cytological Structures.- 9.12.2.1 Ancient Works in Light Microscopy.- 9.12.2.2 Cell Wall Differentiation.- 9.12.2.3 Origin of the Vacuolar Apparatus.- 9.12.2.4 Cytology of the Latex Secretions.- 9.12.2.5 Autophagic Phenomena in Differentiated Laticifers.- 9.12.2.6 Behaviour of Other Organelles.- 9.12.3 Anatomical Localizations.- 9.12.4 Composition and Physical State of the Latex.- 9.12.5 Possible Functions of Laticifers.- References.- III Conclusions.- 1 The Differentiation of Plant Cells.- 2 Dedifferentiation: Common Process of Vascular Plant Ontogeny.- 3 Fundamental Tissues and Accessory Specializations.- 4 The Pectocellulosic Walls, a Specific Feature of the Plant World.- Author Index.