Chapter 6: Anatomy of Flowering Plants

Introduction

• Anatomy: Study of the internal structure and functional organization of higher plants.
• Plants' Internal Structure: Cells are organized into tissues, which form organs.
• Angiosperms: Monocots and dicots have anatomical differences; adaptations to diverse environments.

Tissues in Plants

• Definition: Group of cells with a common origin, usually performing a common function.
• Types:
  • Meristematic Tissues
  • Permanent Tissues

Meristematic Tissues

• Meristems: Regions of active cell division.
  • Apical Meristem: Located at root and shoot tips, produces primary tissues.
  • Intercalary Meristem: Between mature tissues, found in grasses.
  • Lateral Meristem: Forms secondary tissues (e.g., vascular cambium, cork cambium).
• Primary vs Secondary Meristems: Primary appear early, secondary appear later.

Permanent Tissues

• Simple Tissues: Made of one cell type.
  • Parenchyma: Functions in photosynthesis, storage, secretion.
  • Collenchyma: Provides support, found below the epidermis.
  • Sclerenchyma: Provides support; consists of fibers and sclereids.
• Complex Tissues: Made of more than one cell type.
  • Xylem: Conducts water/minerals, provides strength.
  • Phloem: Transports food materials.

Tissue Systems

• Epidermal Tissue System: Outer layer, includes stomata, trichomes, and hairs.
• Ground Tissue System: Includes parenchyma, collenchyma, sclerenchyma.
• Vascular Tissue System: Comprised of xylem and phloem.

Epidermal Tissue System

• Epidermis: Protective outer layer, may have a waxy cuticle.
• Stomata: Bean-shaped cells that regulate gas exchange and transpiration.
• Hairs/Trichomes: Help in water absorption and reduce water loss.

Ground Tissue System

• Components: Cortex, pericycle, pith, medullary rays.
• Function: Photosynthesis, storage, support.

Vascular Tissue System

• Vascular Bundles: Xylem and phloem; types include radial, conjoint, open, closed.

Anatomy of Dicot and Monocot Plants

• Dicot Root: Shows epidermis, cortex, endodermis, pericycle, vascular bundles.
• Monocot Root: Similar to dicot root but with more xylem bundles.
• Dicot Stem: Has epidermis, cortex, pericycle, vascular bundles in a ring.
• Monocot Stem: Scattered vascular bundles, large ground tissue.
• Dicot Leaf (Dorsiventral): Has epidermis, mesophyll (palisade and spongy), vascular system.
• Monocot Leaf (Isobilateral): Stomata on both surfaces, no palisade mesophyll.

Secondary Growth

• Definition: Increase in girth due to lateral meristems.
• Vascular Cambium: Produces secondary xylem and phloem.
• Cork Cambium: Produces cork (protective layer).
• Wood Types: Spring wood, autumn wood, hardwood, sapwood.
• Bark: Includes all tissues outside vascular cambium.

Conclusion

• Plant Tissues: Classified into meristematic and permanent.
• Functions: Assimilation, storage, transport, support.
• Variation: Monocots and dicots differ in internal structure.
• Secondary Growth: Increases girth; involves vascular cambium, cork cambium.