Tepal
A tepal is one of the outer parts of a flower (collectively the perianth). The term is used when these parts cannot easily be classified as either sepals or petals. This may be because the parts of the perianth are undifferentiated (i.e. of very similar appearance), as in Magnolia, or because, although it is possible to distinguish an outer whorl of sepals from an inner whorl of petals, the sepals and petals have similar appearance to one another (as in Lilium). The term was first proposed by Augustin Pyramus de Candolle in 1827 and was constructed by analogy with the terms "petal" and "sepal".[1][2] (De Candolle used the term perigonium or perigone for the tepals collectively; today, this term is used as a synonym for perianth.)[3]
Origin
Undifferentiated tepals are believed to be the ancestral condition in flowering plants. For example, Amborella, which is thought to have separated earliest in the evolution of flowering plants,[4] has flowers with undifferentiated tepals. Distinct petals and sepals would therefore have arisen by differentiation, probably in response to animal pollination. In typical modern flowers, the outer or enclosing whorl of organs forms sepals, specialised for protection of the flower bud as it develops, while the inner whorl forms petals, which attract pollinators.
Tepals formed by similar sepals and petals are common in
In some plants the flowers have no petals, and all the tepals are sepals modified to look like petals. These organs are described as
Properties and shape
Terms used in the description of tepals include pubescent (with dense fine, short, soft hairs, downy), puberulent (minutely pubescent, hairs barely visible to the naked eye) and puberulous (dense covering of very short soft hairs). Tepal shape is described in similar terms to those used for leaves (see Glossary of leaf morphology).
Gallery
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Flowers of Magnolia × alba showing tepals in various stages of development
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Tepals of Magnolia × wieseneri
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A hellebore flower showing the petaloid sepals
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A Sternbergia lutea flower showing the two whorls of tepals
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A tulip flower showing the petal-like tepals
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Tepals oflilioid monocot
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6 tepals (3 inner, 3 outer) of the rush Juncus squarrosus
See also
References
- ^ Augustin Pyramus de Candolle (1827). Organographie végétale, ou Description raisonnée des organes des plantes; pour servir de suite et de développement a la théorie élémentaire de la botanique, et d'introduction a la physiologie végétale et a la physiologie végétale et a la description des familles. Paris: Deterville. p. 503.
- ^ Augustin Pyramus de Candolle (1841). Vegetable organography; or, An analytical description of the organs of plants. Vol. 2. Translated by Boughton Kingdon. London: Houlston & Stoneman. p. 90.
- ISBN 978-0-7153-1643-6. p. 39.
- PMID 17513305.
- Botany: A Brief Introduction To Plant Biology - 5th ed. Thomas L. Rost; T. Elliot Weier - Wiley & Sons 1979 ISBN 0-471-02114-8.
- Plant Systematics - Jones; Samuel - McGraw-Hill 1979 ISBN 0-07-032795-5.