Original Research

The epidermis in Passerina/ (Thymelaeaceae): structure, function and taxonomic significance

C. L. Bredenkamp, A. E. van Wyk
Bothalia | Vol 30, No 1 | a2219 | DOI: https://doi.org/10.4102/abc.v30i1.2219 | © 2000 C. L. Bredenkamp, A. E. van Wyk | This work is licensed under CC Attribution 4.0
Submitted: 03 February 2000 | Published: 03 February 2000

About the author(s)

C. L. Bredenkamp, National Botanical Institute, South Africa
A. E. van Wyk, H.G.W.J. Schweickerdt Herbarium, Department of Botany, University of Pretoria, South Africa

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Epidermal features were studied in all 17 species of Passerina, a genus endemic to southern Africa. Leaves in Passerina are inversely ericoid, the adaxial surface concave and the abaxial surface convex. Leaves are inversely dorsiventral and epistomatic. The adaxial epidermis is villous, with unicellular, uniseriate trichomes and relatively small thin-walled cells, promoting flexibility of leaf margins owing to turgor changes. In common with many other Thymelaeaceae, abaxial epidermal cells are large and tanniniferous with mucilaginous cell walls. The cuticle is adaxially thin, but abaxially well devel­oped, probably enabling the leaf to restrict water loss and to tolerate high light intensity and UV-B radiation. Epicuticular waxes, present in all species, comprise both soft and plate waxes. Epidermal structure proves to be taxonomically impor­tant at family, genus and species levels. Interspecific differences include arrangement of stomata and presence or absence of abaxial epidermal hair. Other diagnostic characters of the abaxial epidermal cells are arrangement,size and shape, cutic- ular ornamentation and presence or absence of wax platelets. Two groups of species on the basis of abaxial epidermal cell orientation are recognised. Many leaf epidermal features in Passerina are interpreted as structural adaptations to the Mediterranean climate of the Cape.


anatomy; cuticle; epicuticular waxes; epidermis; Passerina; southern Africa; stomata; taxonomy; Thymelaeaceae


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