Plant Body and Tissues

Plant Body

• Flowering plants have two major organ systems: the shoot system (leaves, stems, flowers, fruits) and the root system (which absorbs water and minerals).
• The shoot system grows above ground, absorbing light for photosynthesis.
• The root system is typically underground.

Plant Tissues

• A tissue is a group of cells with similar structure and function.
• Plant tissues are categorized into two main types: meristematic and permanent.

Meristematic Tissue

• Immature cells that actively divide.
• Found in stem and root apices, leaf primordia, and vascular/cork cambium.
• Contribute to plant growth.

Meristematic Tissue Characteristics

• Composed of immature cells.
• Lacks intercellular spaces.
• Thin-walled cells.
• Rich in cytoplasm with small vacuoles.

Classification of Meristems

• Based on origin:
  • Primary (derived from promeristem; found at stem and root apices).
  • Secondary (develops from permanent tissues; adds thickness through secondary growth; examples include cork cambium and interfascicular cambium).
• Based on position:
  • Apical (tips of roots and stems, for longitudinal growth).
  • Intercalary (between permanent tissues, increasing internode length).
  • Lateral (laterally on roots and stems, increasing thickness).
  • Based on function (Protoderm, Procambium, and Ground Meristem).

Permanent Tissues

• Mature cells that have stopped dividing.
• Further classified into different types: epidermis, parenchyma, collenchyma, sclerenchyma, and vascular tissue.

Epidermis

• Outermost layer of plants; provides protection.
• Absorbs water and minerals in roots.
• Regulates water loss through transpiration in stems and leaves (via stomata).
• May contain trichomes (hair-like structures).

Parenchyma

• Thin-walled cells; various functions (photosynthesis, storage).
• Types include aerenchyma (air spaces) and chlorenchyma (chlorophyll).

Collenchyma

• Thick-walled cells with cellulose deposits.
• Provides primary support in herbaceous plants.

Sclerenchyma

• Dead cells with heavily thickened secondary walls containing lignin.
• Provides support.
• Types include fibers (elongated) and sclereids.

Vascular Tissue

• (Xylem and Phloem)
  • Xylem transports water and minerals from roots.
  • Phloem transports organic compounds from sites of photosynthesis.
  • Xylem contains tracheids and vessel elements (tubular and elongated; dead at maturity).
  • Phloem contains sieve tubes (alive at maturity) and companion cells.