Trichomes
Trichomes are outgrowths of the epidermis of the leaf, stem or root. Leaf trichomes have a variety of morphologies and functions. Trichomes may be unicellular or multicellular unbranched hairs (Pelargonium); elaborately branched hairs (Viburnum); centrally attached flat scales (Elaeagnus). Some trichomes may also be glandular, producing a variety of secretions (Pelargonium). Substances secreted may include the essential oils which give herbs their characteristic odours and flavours (thyme, mint, lavender); salt (plants from saline habitats); enzymes, nectars and mucilages (insectivorous plants). Non-glandular trichomes may function to protect the plant from water loss, from incident radiation, and from insects and other predators.
Coleus
This plant has both glandular trichomes (shown to the right) and non-glandular trichomes (shown below).
Stevia
This plant is native to Paraguay. It contains a substance that is thousands times sweeter than table sugar in its trichomes.
Elaeagnus
These trichomes are in the form of scales. They have been scraped from the leaves.
Viburnum
These trichomes were scraped from the underside of the leaf and stained with toluidine blue. These trichomes are branched and non-glandular.
