Last updated
Diagram showing the parts of a mature flower. In this example the perianth is separated into a calyx (sepals) and corolla (petals) Mature flower diagram.svg
Diagram showing the parts of a mature flower. In this example the perianth is separated into a calyx (sepals) and corolla (petals)
Tetramerous flower of Ludwigia octovalvis showing petals and sepals. Petal-sepal.jpg
Tetramerous flower of Ludwigia octovalvis showing petals and sepals.
After blooming, the sepals of Hibiscus sabdariffa expand into an edible accessory fruit Terengganu roselle.jpg
After blooming, the sepals of Hibiscus sabdariffa expand into an edible accessory fruit
In many Fabaceae flowers, a calyx tube surrounds the petals. Vicia February 2008-1.jpg
In many Fabaceae flowers, a calyx tube surrounds the petals.
The large calyx of the medlar fruit is the source of its vulgar nicknames. 20170919Crataegus germanica2.jpg
The large calyx of the medlar fruit is the source of its vulgar nicknames.

A sepal ( /ˈsɛpəl/ or /ˈspəl/ ) [1] [2] [3] is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom. [4] The term sepalum was coined by Noël Martin Joseph de Necker in 1790, and derived from Greek σκέπη skepē 'covering'. [5] [6]

Collectively the sepals are called the calyx (plural calyces), [7] the outermost whorl of parts that form a flower. The word calyx was adopted from the Latin calyx , [8] not to be confused with calix 'cup, goblet'. [9] Calyx is derived from Greek κάλυξ kalyx 'bud, calyx, husk, wrapping' (cf. Sanskrit kalika 'bud'), [10] while calix is derived from Greek κύλιξ kylix 'cup, goblet', and the words have been used interchangeably in botanical Latin. [11]

After flowering, most plants have no more use for the calyx which withers or becomes vestigial. Some plants retain a thorny calyx, either dried or live, as protection for the fruit or seeds. Examples include species of Acaena , some of the Solanaceae (for example the Tomatillo, Physalis philadelphica), and the water caltrop, Trapa natans. In some species the calyx not only persists after flowering, but instead of withering, begins to grow until it forms a bladder-like enclosure around the fruit. This is an effective protection against some kinds of birds and insects, for example in Hibiscus trionum and the Cape gooseberry. In other species, the calyx grows into an accessory fruit.

Morphologically, both sepals and petals are modified leaves. The calyx (the sepals) and the corolla (the petals) are the outer sterile whorls of the flower, which together form what is known as the perianth . [12] Similarly to ordinary leaves, sepals are capable of performing photosynthesis. However, photosynthesis in sepals occurs at a slower rate than in ordinary leaves due to sepals having a lower stomatal density which limits the spaces for gas exchange. [13]

The term tepal is usually applied when the parts of the perianth are difficult to distinguish, [14] e.g. the petals and sepals share the same color, or the petals are absent and the sepals are colorful. When the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly coloured tepals. Since they include Liliales, an alternative name is lilioid monocots. 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. [ 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 development and form of the sepals vary considerably among flowering plants. [15] They may be free (polysepalous) or fused together (gamosepalous). [16] 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.

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 family Lythraceae, [17] and Fabaceae). In other flowers (e.g., Rosaceae, Myrtaceae) a hypanthium includes the bases of sepals, petals, and the attachment points of the stamens.

Mechanical cues may be responsible for sepal growth and there is a strong evidence suggesting that microtubules are present and determine the tensile strength and direction of growth at a molecular level. [18]

See also

Related Research Articles


In angiosperms, a hypanthium or floral cup is a structure where basal portions of the calyx, the corolla, and the stamens form a cup-shaped tube. It is sometimes called a floral tube, a term that is also used for corolla tube and calyx tube. It often contains the nectaries of the plant. It is present in most flowering species, although varies in structural dimensions and appearance. This differentiation between the hypanthium in particular species is useful for identification. Some geometric forms are obconic shapes as in toyon, whereas some are saucer-shaped as in Mitella caulescens.

Petal Part of most types of flower

Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called the corolla. Petals are usually accompanied by another set of modified leaves called sepals, that collectively form the calyx and lie just beneath the corolla. The calyx and the corolla together make up the perianth. When the petals and sepals of a flower are difficult to distinguish, they are collectively called tepals. Examples of plants in which the term tepal is appropriate include genera such as Aloe and Tulipa. Conversely, genera such as Rosa and Phaseolus have well-distinguished sepals and petals. When the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly colored tepals. Since they include Liliales, an alternative name is lilioid monocots.

Stamen The male organ of a flower

The stamen is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium.

Lythraceae Family of flowering plants

Lythraceae is a family of flowering plants, including 32 genera, with about 620 species of herbs, shrubs, and trees. The larger genera include Cuphea, Lagerstroemia (56), Nesaea (50), Rotala (45), and Lythrum (35). It also includes the pomegranate and the water caltrop. Lythraceae has a worldwide distribution, with most species in the tropics, but ranging into temperate climate regions as well.


A tepal is one of the outer parts of a flower. 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, 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. The term was first proposed by Augustin Pyramus de Candolle in 1827 and was constructed by analogy with the terms "petal" and "sepal".

Floral symmetry Shape of flowers

Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts.

Perianth The collective term for the sepals and petals, or either of them if one is absent. the outer part of a flower, consisting of the calyx and corolla

The perianth is the non-reproductive part of the flower, and structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla (petals) or tepals when called a perigone. The term perianth is derived from Greek περί and άνθος, while perigonium is derived from περί and γόνος . In the mosses and liverworts (Marchantiophyta), the perianth is the sterile tubelike tissue that surrounds the female reproductive structure.

<i>Eupomatia</i> Genus of flowering plants

Eupomatia is a genus of three flowering shrub species known to science, of the Australian continent ancient family Eupomatiaceae. The Eupomatiaceae have been recognised by most taxonomists and classified in the plant order Magnoliales. The three species of shrubs or small trees grow naturally in the rainforests and humid eucalypt forests of eastern Australia and New Guinea. The type species Eupomatia laurina was described in 1814 by Robert Brown.

Operculum (botany)

In botany, an operculum is a cap-like structure in some flowering plants, mosses, and fungi.

Flower Structure found in some plants; aka: blossom

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants. The biological function of a flower is to facilitate reproduction, usually by providing a mechanism for the union of sperm with eggs. Flowers may facilitate outcrossing resulting from cross pollination or allow selfing when self-pollination occurs.

This page provides a glossary of plant morphology. Botanists and other biologists who study plant morphology use a number of different terms to classify and identify plant organs and parts that can be observed using no more than a handheld magnifying lens. This page provides help in understanding the numerous other pages describing plants by their various taxa. The accompanying page—Plant morphology—provides an overview of the science of the external form of plants. There is also an alphabetical list: Glossary of botanical terms. In contrast, this page deals with botanical terms in a systematic manner, with some illustrations, and organized by plant anatomy and function in plant physiology.

This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary of leaf morphology. For other related terms, see Glossary of phytopathology and List of Latin and Greek words commonly used in systematic names.

Whorl (botany)

In botany, a whorl or verticil is an arrangement of leaves, sepals, petals, stamens, or carpels that radiate from a single point and surround or wrap around the stem or stalk. A leaf whorl consists of at least three elements; a pair of opposite leaves is not called a whorl.

Lilioid monocots Grade of flowering plant orders, within Lilianae

Lilioid monocots is an informal name used for a grade of five monocot orders in which the majority of species have flowers with relatively large, coloured tepals. This characteristic is similar to that found in lilies ("lily-like"). Petaloid monocots refers to the flowers having tepals which all resemble petals (petaloid). The taxonomic terms Lilianae or Liliiflorae have also been applied to this assemblage at various times. From the early nineteenth century many of the species in this group of plants were put into a very broadly defined family, Liliaceae sensu lato or s.l.. These classification systems are still found in many books and other sources. Within the monocots the Liliaceae s.l. were distinguished from the Glumaceae.


In plant morphology, a cataphyll is a reduced, small leaf. Many plants have both "true leaves" (euphylls) which perform the majority of photosynthesis, and cataphylls that are modified to perform other specialized functions. Cataphylls include bracts, bracteoles, and bud scales, as well as any small leaves that resemble scales, which are known as scale leaves. Some cataphylls have a primary function other than photosynthesis. The functions of cataphylls such as bud scales may be short-lived and they are often shed after the need for them is past.

Floral formula Floral formula is a means to representation of the structure of a flower using numbers, letters and various symbols, presenting substantial information about the flower in a compact form.

Floral formula is a means to represent the structure of a flower using numbers, letters and various symbols, presenting significant information about the flower in a compact form. It can represent particular species or can be generalized to characterize higher taxa, usually giving ranges of organ numbers. Floral formulae are one of the two ways of describing flower structure developed during the 19th century, the other being floral diagrams. The format of floral formulae differs between authors, yet they tend to convey the same information.

<i>Paris polyphylla</i> Species of flowering plant

Paris polyphylla is an Asian species of flowering plant native to China, Taiwan, the Indian Subcontinent, and Indochina. It produces spider-like flowers that throw out long, thread-like, yellowish green petals throughout most of the warm summer months and into the autumn. In the fall, the flowers are followed by small, scarlet berries. It is a perennial, which slowly spreads, is fully hardy in Britain, and survives in leafy, moist soil in either complete or partial shade.

Calochortoideae Subfamily of flowering plants

The Calochortoideae are a subfamily of monocotyledon perennial, herbaceous mainly bulbous flowering plants in the lily family, Liliaceae. Approximately the same group of species has been recognized as a separate family, Calochortaceae, in a few systems of plant taxonomy, including the Dahlgren system. They are found predominantly in the temperate regions of the Northern Hemisphere, particularly East Asia and North America.

<i>Berberidopsis beckleri</i> Species of flowering plant

Berberidopsis beckleri is a species of climbing plant found in cool rainforests in eastern Australia. Ferdinand von Mueller described the plant as Streptothamnus beckleri from collections at the Clarence River.

<i>Habenaria chlorosepala</i> Species of orchid

Habenaria chlorosepala, commonly known as the green-hooded rein orchid, is a species of orchid that is endemic to a small area in far north Queensland. It has two or three leaves at its base and up to twenty small green and white flowers.


  1. From French sépale, from New Latin sepalum, a blend of sep- from Greek skepē 'covering' and -alum from New Latin petalum 'petal', influenced by French pétale 'petal'.
  2. "Oxford dictionary".
  3. "Collins dictionary".
  4. Beentje, Henk (2010). The Kew Plant Glossary. Richmond, Surrey: Royal Botanic Gardens, Kew. ISBN   978-1-84246-422-9., p. 106
  5. Stearn, William T. (2000). Botanical Latin, 4th ed.: 38-39. ISBN   0-88192-321-4
  6. Necker, N.J. de (1790). Corollarium ad Philosophiam botanicam Linnaei 18, 31
  7. Shorter Oxford English dictionary, 6th ed. United Kingdom: Oxford University Press. 2007. p. 3804. ISBN   978-0199206872.
  8. Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928
  9. John Entick, William Crakelt, Tyronis thesaurus, or, Entick's new Latin English dictionary. Publisher: E.J. Coale, 1822
  10. Tucker, T. G. (1931). A Concise Etymological Dictionary of Latin. Halle (Saale): Max Niemeyer Verlag.
  11. Stearn, William T. (2000). Botanical Latin, 4th ed.: 38
  12. 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. p. 106. ISBN   0-521-29359-6.
  13. Aschan, G.; Pfanz, H.; Vodnik, D.; Batič, F. (2005-03-01). "Photosynthetic performance of vegetative and reproductive structures of green hellebore (Helleborus viridis L. agg.)". Photosynthetica. 43 (1): 55–64. doi:10.1007/s11099-005-5064-x. S2CID   24426595.
  14. Beentje 2010 , p. 119
  15. Sattler, R. 1973. Organogenesis of Flowers. A Photographic Text-Atlas. University of Toronto Press. ISBN   0-8020-1864-5.
  16. Beentje 2010, pp. 51 & 91.
  17. Carr, Gerald. "Lythraceae". University of Hawaii. Archived from the original on 2008-12-05. Retrieved 2008-12-20.
  18. Hervieux, Nathan; Dumond, Mathilde; Sapala, Aleksandra; Routier-Kierzkowska, Anne-Lise; Kierzkowski, Daniel; Roeder, Adrienne H.K.; Smith, Richard S.; Boudaoud, Arezki; Hamant, Olivier (April 2016). "A Mechanical Feedback Restricts Sepal Growth and Shape in Arabidopsis". Current Biology. 26 (8): 1019–1028. doi: 10.1016/j.cub.2016.03.004 . PMID   27151660.