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What are trichomes? Write their function in angiosperms.

GeneralClass 12AllAnswered 27 Mar 2026
Answer

Trichomes are epidermal appendages (outgrowths) found on the surface of plants.

Structural Diversity:

Based on Cellularity:

  • Unicellular: Single-celled (root hairs, cotton fibers)
  • Multicellular: Multi-celled (common in shoot systems)

Based on Branching:

  • Branched: Stellate (star-shaped) trichomes
  • Unbranched: Simple hair-like structures

Based on Texture:

  • Soft: Non-lignified
  • Stiff: Sclerenchymatous, lignified

Functions in Angiosperms:

  1. Reduce Transpiration:
    • Create a boundary layer of still air
    • Reflects light → reduces leaf temperature
    • Example: Nerium (oleander), desert plants
  2. Protection:
    • Physical barrier against herbivores (stinging hairs in Urtica - nettle)
    • Chemical defense via secretory trichomes (essential oils, toxins)
  3. Temperature Regulation:
    • White/reflective trichomes reduce heat absorption
    • Example: Alpine plants
  4. Secretion:
    • Glandular trichomes secrete:
      • Essential oils (mint, lavender)
      • Mucilage (insectivorous plants)
      • Resins and alkaloids
  1. Nutrient Absorption:
    • Root hairs (unicellular trichomes) absorb water and minerals
    • Increase surface area manifold

Commercial Importance:

  • Cotton fibers are seed trichomes
  • Essential oil production (rose, lavender)

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