Plant Structure, Growth, and Development

Kingdom: Plantae

  • Focus of study: Plant structure, growth, and development
  • Relevant course: BIOL-112, Chapter 33

Shoot and Root Systems

  • Shoot System: Comprises stems and leaves where photosynthesis occurs.

    • Components Include:
    • Terminal bud
    • Axillary bud
    • Node and Internode
    • Phytomer (basic unit of plant growth)
    • Petiole (leaf stalk)
    • Leaf (Blade)
    • Branch

  • Root System: Serves to anchor the plant and supply water and nutrients.

Tissue Systems in Plants

  • Dermal Tissue System: Protective layer; includes epidermis and guard cells.
  • Vascular Tissue System: Involved in transport; includes xylem and phloem.
  • Ground Tissue System: Majority of plant body; includes parenchyma, collenchyma, and sclerenchyma.

Ground Tissue System

  • 3 Simple Tissues:
    • Parenchyma
    • Most common type of cell.
    • Functions in storage, photosynthesis.
    • Ability to differentiate in case of injury.
    • Collenchyma
    • Provides flexible support, especially in young plants.
    • Characteristics: elongated, uneven cell wall thickening.
    • Sclerenchyma
    • Provides structural support; cells often dead at maturity.
    • Has sclereids (in nuts and stones) and fibers (in wood and bark).

Vascular Tissue System

  • Xylem: Conducts water and minerals; provides support.
    • Cell Types: Tracheids and vessel elements conduct water; fibers provide support.
  • Phloem: Conducts food materials, supports plant structure.
    • Cell Types: Sieve tube elements (conduct sugars), companion cells (assist sieve tubes).

Dermal Tissue System

  • Epidermis: Protective outer layer; secretes cuticle to reduce water loss.
    • Contains guard cells regulating stomata for gas exchange.
    • Trichomes: Provide protection; reduce water loss.
  • Periderm: Formed under epidermis in woody plants; aids in protection and water loss reduction.

Plant Growth

  • Growth Areas: Occurs in meristems, with meristematic cells functioning like stem cells.
Types of Growth
  • Indeterminate Growth: Roots and stems grow throughout a plant’s life.
  • Determinate Growth: Growth ceases when a certain size is reached (leaves/flowers).
Primary vs. Secondary Growth
  • Primary Growth: Increase in length; involves apical meristems at tips of roots and shoots.
  • Secondary Growth: Increase in girth; due to lateral meristems, primarily in woody plants.
Apical and Lateral Meristems
  • Apical Meristems: Located at tips of roots and shoots; responsible for primary growth.
  • Lateral Meristems: Include vascular cambium (adds wood) and cork cambium (adds bark).
Bark Structure
  • Comprises all tissues outside the vascular cambium:
    • Inner bark (living, secondary phloem)
    • Outer bark (mostly dead, composed of periderm).

Plant Development and Morphogenesis

  • Factors Influencing Plant Form:
    • Plane and symmetry of cell division.
    • Orientation of cellulose in cell walls directing expansion.
    • Morphogenesis through cellular pattern formation and differentiation depending on cell location.