Sepal
A sepal (from Latin separatus "separate" + petalum "petal"[citation needed]) is a part of the flower of angiosperms (flowering plants). Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud.[1] Another common function of sepals is protection from insect attack, and when there is no such protection, there often is some other ecological strategy, such as poison.[citation needed]
Morphologically both sepals and petals are modified leaves. The calyx (plural, calices, the sepals) and the corolla (the petals) are the outer sterile whorls of the flower, which together form what is known as the perianth.[2]
The term tepal is usually applied when the parts of the perianth are difficult to distinguish,[3] e.g. the petals and sepals share the same color, or the petals are absent and the sepals are colorful. Examples of plants in which the term tepal is appropriate include genera such as Aloe and Tulipa. In contrast, genera such as Rosa and Phaseolus have well-distinguished sepals and petals.
Commonly in plants such as Tulipa, that have tepals, the sepals are hardly more robust than the petals, and such plants either come from warm temperate zones, or flower mainly in mild seasons, such as late spring.[citation needed]
The number of sepals in a flower is its merosity. Flower merosity is indicative of a plant's classification. The merosity of a eudicot flower is typically four or five. The merosity of a monocot or palaeodicot flower is three, or a multiple of three.
The forms of the sepals vary considerably among flowering plants. Often, the sepals are much reduced, appearing somewhat awn-like, or as scales, teeth, or ridges. Most often such structures protrude until the fruit is mature and falls off. Some however, remain as tough or thorny protection for the fruit. Although the sepal withers in most plants, or at any rate does not grow after the fruit has been fertilised, in some species, such as the cape gooseberry, the fused part of the calyx grows and encloses the ripening fruit practically entirely, forming a protective papery cape.
Examples of flowers with much reduced perianths are found among the grasses. In some flowers, the sepals are fused towards the base, forming a calyx tube (as in the Lythraceae family),[4] a floral tube that can include the petals and the attachment point of the stamens.
[edit] References
- ^ Beentje, Henk (2010). The Kew Plant Glossary. Richmond, Surrey: Royal Botanic Gardens, Kew. ISBN 978-1-84246-422-9, p. 106
- ^ Davis, P.H.; Cullen, J. (1979). The identification of flowering plant families, including a key to those native and cultivated in north temperate regions. Cambridge: Cambridge University Press. pp. 106. ISBN 0521293596.
- ^ Beentje 2010, p. 119
- ^ Carr, Gerald. "Lythraceae". University of Hawaii. http://www.botany.hawaii.edu/FACULTY/CARR/lythr.htm. Retrieved 2008-12-20.
