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A sepal ( or ) is a part of the
flower A flower, sometimes known as a bloom or blossom Cherry blossoms in Paris in full bloom. In botany, blossoms are the flowers of stone fruit fruit tree, trees (genus ''Prunus'') and of some other plants with a similar appearance that flower prof ...

flower
of
angiosperms Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...
(flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the
petal upright=1.4, Diagram showing the parts of a mature flower. In this example the perianth is separated into a calyx (sepals) and corolla (petals) Petals are modified leaves A leaf (plural leaves) is the principal lateral appendage of the ...

petal
s when in bloom., p. 106 The term ''sepalum'' was coined by
Noël Martin Joseph de Necker Noël Martin Joseph Necker (25 December 1730 – 30 December 1793) was a Belgian Belgians ( nl, Belgen, french: Belges, german: Belgier) are people identified with the Kingdom of Belgium, a federal state in Western Europe. As Belgium is a ...
in 1790, and derived from
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
'covering'. Collectively the sepals are called the calyx (plural calyces), the outermost whorl of parts that form a flower. The word ''calyx'' was adopted from the Latin ,Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928 not to be confused with 'cup, goblet'. ''Calyx'' is derived from Greek 'bud, calyx, husk, wrapping' ( Sanskrit 'bud'), while is derived from Greek 'cup, goblet', and the words have been used interchangeably in botanical Latin. 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 ''Acaena'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including their an ...
'', some of the
Solanaceae The Solanaceae , or nightshades, are a family (biology), family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spice ...
(for example the
Tomatillo The tomatillo (''Physalis philadelphica'' and ''Physalis ixocarpa''), also known as the Mexican husk tomato, is a plant of the nightshade family bearing small, spherical and green or green-purple fruit of the same name. Tomatillos originated in ...

Tomatillo
, ''Physalis philadelphica''), and the
water caltrop The water caltrop is any of three extant species of the genus ''Trapa'': ''Trapa natans'', ''Trapa bicornis'' and the endangered ''Trapa rossica''. It is also known as buffalo nut, bat nut, devil pod, ling nut, ''lin kok, ling jow'', ling kio nut ...
, ''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 ''Hibiscus trionum'', commonly called flower-of-an-hour, bladder hibiscus, bladder ketmia, bladder weed, modesty, puarangi, shoofly, and venice mallow, is an annual plant Image:Doperwt rijserwt peulen Pisum sativum.jpg, 240px, Peas are an annua ...

Hibiscus trionum
'' and the
Cape gooseberry
Cape gooseberry
. In other species, the calyx grows into an
accessory fruit Accessory may refer to: * Accessory (legal term) An accessory is a person who assists in the commission of a crime In ordinary language, a crime is an unlawful act punishable by a state or other authority. The term ''crime'' does not, in ...
. 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 A mature flower. In this example the perianth is separated into a calyx (sepals) and corolla (petals) The perianth (perigonium, perigon or perigone in monocots) is the non-reproductive part of the flower A flower, sometimes known as a bloom or ...
''. Similarly to ordinary leaves, sepals are capable of performing
photosynthesis Photosynthesis is a process used by plants and other organisms to into that, through , can later be released to fuel the organism's activities. Some of this chemical energy is stored in molecules, such as s and es, which are synthesized fro ...

photosynthesis
. However, photosynthesis in sepals occurs at a slower rate than in ordinary leaves due to sepals having a lower
stoma File:LeafUndersideWithStomata.jpg, The underside of a leaf. In this species (''Tradescantia zebrina'') the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigme ...

stoma
tal density which limits the spaces for gas exchange. The term ''
tepal A tepal is one of the outer parts of a flower A flower, sometimes known as a bloom or blossom, is the reproduction, reproductive structure found in flowering plants (plants of the division Magnoliophyta, also called angiosperms). The biological ...
'' is usually applied when the parts of the perianth are difficult to distinguish, 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 Lilioid monocots (lilioids, liliid monocots, petaloid monocots, petaloid lilioid monocots) is an informal name used for a grade Grade or grading may refer to: Arts and entertainment * Grade (band) Grade is a melodic hardcore band from Canada ...
, orders of monocots with brightly colored tepals. Since they include
Liliales Liliales is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and ...
, an alternative name is lilioid monocots. Examples of plants in which the term tepal is appropriate include genera such as ''
Aloe ''Aloe'' ( , ), also written ''Aloë'', is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and livin ...

Aloe
'' and ''
Tulipa Tulips (''Tulipa'') are a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification ...

Tulipa
''. In contrast, genera such as ''
Rosa Rosa or De Rosa may refer to: People *Rosa (given name) *Rosa (surname) Places *223 Rosa, an asteroid *Rosa, Alabama, United States *Rosa, Germany, in Thuringia, Germany *Rösa, a village and former municipality in Saxony-Anhalt, Germany *Rosà ...

Rosa
'' and ''
Phaseolus ''Phaseolus'' (bean, wild bean) is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classi ...
'' have well-distinguished sepals and petals. The number of sepals in a flower is its
merosityMerosity (from the greek "méros," which means "having parts") refers to the number of component parts in a distinct whorl of a plant structure. It is most commonly used in the context of flowers where it refers to the number of sepal Image:Mature ...
. Flower merosity is indicative of a plant's classification. The merosity of a
eudicot The eudicots, Eudicotidae or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non-magnoliid dicots b ...
flower is typically four or five. The merosity of a
monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. The ...
or palaeodicot flower is three, or a multiple of three. The development and form of the sepals vary considerably among
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s. They may be free (polysepalous) or fused together (gamosepalous). 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 Poaceae () or Gramineae () is a large and nearly ubiquitous Family (biology), family of monocotyledonous flowering plants known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in ...
. In some flowers, the sepals are fused towards the base, forming a calyx tube (as in the family
Lythraceae Lythraceae is a family (biology), family of flowering plants, including 32 genus, genera, with about 620 species of herbs, shrubs, and trees. The larger genera include ''Cuphea'' (275 spp.), ''Lagerstroemia'' (56), ''Nesaea'' (50), ''Rotala (plan ...
, and
Fabaceae The Fabaceae or Leguminosae,International Code of Nomenc ...

Fabaceae
). In other flowers (e.g., Rosaceae, Myrtaceae) a
hypanthium 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. I ...
includes the bases of sepals, petals, and the attachment points of the
stamen The stamen (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ve ...
s. 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.


See also

*
Plant morphology Phytomorphology is the study of the physical form and external structure of plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy ...

Plant morphology


References

{{Authority control
Plant morphology ''Plant morphology'' is the field in botany that studies the diversity in forms, with the naked eye or slight optical magnification. This is opposed to plant anatomy (see :Plant anatomy) that needs to cut into plants to be able to study its subject, ...