Trichomes and Leaf Appendages (Stipules)
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.
Viburnum
This picture shows the bottom surface of the leaf (pictured above) and the top of the leaf (pictured below)
The underside is fuzzy looking.
These trichomes were scraped from the underside of the leaf and stained with toluidine blue. These trichomes are branched and non-glandular.
Elaeagnus
This picture shows the top surface of the leaf (pictured above) and the bottom of the leaf (pictured below)
These trichomes are in the form of scales. They have been scraped from the leaves.
LEAF APPENDAGES
There are numerous types of leaf appendages. In lab we looked at the stipules of Begonia. Stipules are small paired structures found at the base of the leaf of some plants. They are indicated in the diagram with arrows.
In the plant modifications section of the website and lab you will have the opportunity to examine leaf tendrils. These leaf appendages are modifications of leaflets.
MESOPHYTES (there is no shortage of available water)
XEROPHYTES (dry habitat)
HYDROPHYTES (lots of water)
TRICHOMES AND LEAF APPENDAGES
LEAF MODIFICATIONS
BACK TO LEAF FRONTPAGE