What is a Trichome?
Trichomes are the hairs, prickles, scales, and glandular structures found on plant surfaces. They range from invisible fuzz to prominent bristles and serve a surprising variety of functions — from deterring herbivores to trapping moisture.
Types
Non-Glandular (Structural)
- Simple hairs: Single-celled or multicellular straight hairs.
- Stellate (star-shaped): Multiple branches radiating from a base — common in tropical trees.
- Peltate (shield-shaped): Flat, disc-like scales — found on Bromeliaceae.
- Dendritic (tree-shaped): Branching like a miniature tree.
Glandular (Secretory)
- Capitate: Stalked with a secretory head — produces oils, nectar, or defensive compounds.
- Stinging hairs: Hollow hairs filled with irritating chemicals (e.g., Urtica).
Functions
- Herbivore defense: Dense trichomes deter insect feeding.
- Water retention: Trap moisture from fog and dew.
- UV protection: Shield leaf cells from intense tropical sun.
- Temperature regulation: Create an insulating air layer on the leaf surface.
- Chemical warfare: Glandular trichomes secrete toxic or repellent compounds.
Costa Rican Examples
Balsa (Ochroma pyramidale)
Young leaves are covered in stellate trichomes that give them a fuzzy, silvery appearance.
Ceiba (Ceiba pentandra)
Seed-bearing capsules contain silky trichome-like fibers (kapok) used for stuffing and insulation.
Why It Matters
- Identification: Trichome type, density, and distribution are key diagnostic features for species identification.
- Ecology: Trichome defenses shape plant-herbivore interactions.
- Applied science: Understanding trichome chemistry has applications in natural pesticide development.