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A flower, sometimes known as a bloom or
blossom Image:Cerisier du Japon Prunus serrulata.jpg, 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 profusely f ...

blossom
, is the
reproductive Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual orga ...

reproductive
structure found in
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 (plants of the division
Magnoliophyta Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...
, also called
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 ...
). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism for the union of
sperm Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as ...

sperm
with eggs. Flowers may facilitate outcrossing (fusion of sperm and eggs from different individuals in a population) resulting from cross-pollination or allow selfing (fusion of sperm and egg from the same flower) when self-pollination occurs. The two types of pollination are: self-pollination and cross-pollination.
Self-pollination Self-pollination is a form of pollination in which pollen from the same plant arrives at the Stigma (botany), stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). There are two types of self-pollination: in autogamy, pollen is ...
happens when the pollen from the anther is deposited on the stigma of the same flower, or another flower on the same plant.
Cross-pollination Pollination is the transfer of pollen Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are microsporophytes of seed plants The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams ...
is the transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species. Self-pollination happens in flowers where the stamen and carpel mature at the same time, and are positioned so that the pollen can land on the flower's stigma. This pollination does not require an investment from the plant to provide nectar and pollen as food for pollinators. Some flowers produce diaspores without fertilization (
parthenocarpy In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes know ...
). Flowers contain
sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. All plants, fungus, fungi, and many other lineages for ...
and are the site where
gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all ...
s develop. Many flowers have evolved to be attractive to animals, so as to cause them to be vectors for the transfer of
pollen Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the ga ...

pollen
. After fertilization, the
ovary The ovary is an organ found in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the b ...
of the flower develops into
fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the ...

fruit
containing
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seed
s. In addition to facilitating the reproduction of flowering plants, flowers have long been admired and used by humans to bring beauty to their environment, and also as objects of romance, ritual, esotericism,
witchcraft In many cultures, witchcraft traditionally means the use of magic or supernatural powers, usually to harm others. A practitioner is a witch. In medieval and early modern Europe, where the term ''witchcraft'' originated, accused witches were ...

witchcraft
,
religion Religion is a social Social organisms, including humans, live collectively in interacting populations. This interaction is considered social whether they are aware of it or not, and whether the exchange is voluntary/involuntary. Etymology ...

religion
,
medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge), skills (proced ...

medicine
, and as a source of
food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential nutrients, such as carbohydrates, fats, protein (nutrient), proteins, vi ...

food
.


Etymology

Flower is from the
Middle English Middle English (abbreviated to ME) was a form of the English language spoken after the Norman conquest of England, Norman conquest (1066) until the late 15th century. The English language underwent distinct variations and developments following ...
enm, flour, label=none, which referred to both the
ground grain
ground grain
and the reproductive structure in plants, before splitting off in the 17th century. It comes originally from the
Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an appa ...

Latin
name of the Italian goddess of flowers,
Flora Flora is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. Sometimes bacteria and fungi are also referred to as flora, as in the terms ' ...
. The early word for flower in English was ''blossom'', though it now refers to flowers only of
fruit tree 250px, An almond tree in bloom A fruit tree is a tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of ...

fruit tree
s.


Morphology


Parts

The flower has two essential parts: the vegetative part, consisting of petals and associated structures in the perianth, and the reproductive or sexual parts. A stereotypical flower consists of four kinds of structures attached to the tip of a short stalk. Each of these kinds of parts is arranged in a whorl on the
receptacle Receptacle may refer to: Biology * Receptacle (botany), a plant anatomical part * Seminal receptacle, a sperm storage site in some insects Electrical engineering * Auxiliary car power outlet, formerly known as ''Cigarette lighter receptacle'', a ...
. The four main whorls (starting from the base of the flower or lowest node and working upwards) are as follows:


Perianth

Collectively the calyx and corolla form 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 ...
(see diagram). * '' Calyx'': The calyx consists of leaf-like structures at the base of a flower that protect the flower during development. The leaf-like structures are individually referred to as sepals. There are often as many of these sepals as there are petals. While most calyces are green, there are exceptions in which the calyx is the same color as the petals of the flower or a different color altogether. The calyx performs a crucial role for the flowering plant. As the flower is forming, it is closed tightly into a bud. The sepals are the outer covering of the flower as it forms and are the only thing you see of the flower while it is still in bud form. It protects the developing flower and prevents it from drying out. * ''
Corolla Corolla may refer to: *Corolla (botany) 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) The perianth (perigonium, perigon or perigone in monocots) is ...

Corolla
'': the next whorl toward the apex, composed of units called ''
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'', which are typically thin, soft and colored to attract animals that help the process of
pollination Pollination is the transfer of pollen from an anther (male part) of a plant to the stigma (female part) of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by Anemophily, wind. Pollinating agents are a ...

pollination
. *'' Perigone'': in monocots the calyx and corolla are indistinguishable thus the whorls of the perianth or perigone are called ''
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 ...
s''.


Reproductive

* ''
Androecium The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament and ...

Androecium
'' (from Greek ''andros oikia'': man's house): the next whorl (sometimes multiplied into several whorls), consisting of units called
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 vers ...
s. Stamens consist of two parts: a stalk called a
filament The word filament, which is descended from Latin ''filum'' meaning " thread", is used in English for a variety of thread-like structures, including: In commerce * Fiber Fiber or fibre (from la, fibra, links=no) is a natural or #Man-made f ...
, topped by an
anther The stamen (plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity greate ...
where
pollen Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the ga ...

pollen
is produced by meiosis and eventually dispersed. * ''
Gynoecium Gynoecium (; ) is most commonly used as a collective term for the 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, ...

Gynoecium
'' (from Greek ''gynaikos oikia'': woman's house): the innermost whorl of a flower, consisting of one or more units called carpels. The
carpel Gynoecium (; ) is most commonly used as a collective term for the 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, ...
or multiple fused carpels form a hollow structure called an ovary, which produces ovules internally. Ovules are megasporangia and they in turn produce megaspores by meiosis which develop into female gametophytes. These give rise to egg cells. The gynoecium of a flower is also described using an alternative terminology wherein the structure one sees in the innermost whorl (consisting of an ovary, style and stigma) is called a
pistil '' stigmas and style Gynoecium (, from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided in ...
. A pistil may consist of a single carpel or a number of carpels fused together. The sticky tip of the pistil, the stigma, is the receptor of pollen. The supportive stalk, the style, becomes the pathway for
pollen tube A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
s to grow from pollen grains adhering to the stigma. The relationship to the gynoecium on the receptacle is described as hypogynous (beneath a superior ovary), perigynous (surrounding a superior ovary), or epigynous (above inferior ovary).


Structure

Although the arrangement described above is considered "typical", plant species show a wide variation in floral structure. These modifications have significance in the evolution of flowering plants and are used extensively by botanists to establish relationships among plant species. The four main parts of a flower are generally defined by their positions on the receptacle and not by their function. Many flowers lack some parts or parts that may be modified into other functions and/or look like what is typically another part. In some families, like
Ranunculaceae Ranunculaceae (buttercup or crowfoot family; Latin "little frog", from "frog") is a family (biology), family of over 2,000 known species of flowering plants in 43 genera, distributed worldwide. The largest genera are ''Ranunculus'' (600 specie ...
, the petals are greatly reduced and in many species, the sepals are colorful and petal-like. Other flowers have modified stamens that are petal-like; the double flowers of
Peonie The peony or paeony is a flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek Greek may refer to: Greece Anything of, from, or ...
s and
Rose A rose is a woody perennial plant, perennial flowering plant of the genus ''Rosa'', in the family Rosaceae, or the flower it bears. There are over three hundred Rose species, species and Garden roses, tens of thousands of cultivars. They form ...

Rose
s are mostly petaloid stamens. Flowers show great variation and plant scientists describe this variation in a systematic way to identify and distinguish species. Specific terminology is used to describe flowers and their parts. Many flower parts are fused together; fused parts originating from the same whorl are connate, while fused parts originating from different whorls are adnate; parts that are not fused are free. When petals are fused into a tube or ring that falls away as a single unit, they are sympetalous (also called gamopetalous). Connate petals may have distinctive regions: the cylindrical base is the tube, the expanding region is the throat and the flaring outer region is the limb. A sympetalous flower, with bilateral symmetry with an upper and lower lip, is bilabiate. Flowers with connate petals or sepals may have various shaped corolla or calyx, including campanulate, funnelform, tubular, urceolate, salverform, or rotate. Referring to "fusion," as it is commonly done, appears questionable because at least some of the processes involved may be non-fusion processes. For example, the addition of intercalary growth at or below the base of the primordia of floral appendages such as sepals, petals, stamens and carpels may lead to a common base that is not the result of fusion. Many flowers have some form of symmetry. When 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 ...
is bisected through the central axis from any point and symmetrical halves are produced, the flower is said to be
actinomorphic Floral symmetry describes whether, and how, 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). T ...

actinomorphic
or regular, e.g. rose or trillium. This is an example of
radial symmetry Symmetry in biology refers to the symmetry observed in organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are ...
. When flowers are bisected and produce only one line that produces symmetrical halves, the flower is said to be irregular or
zygomorphic Floral symmetry describes whether, and how, 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). T ...
, e.g. snapdragon or most orchids. Flowers may be directly attached to the plant at their base (sessile—the supporting stalk or stem is highly reduced or absent). The stem or stalk subtending a flower is called a peduncle. If a peduncle supports more than one flower, the stems connecting each flower to the main axis are called
pedicels Image:Delphinium nuttallianum 15498.JPG, The inflorescence of ''Delphinium nuttallianum''. Each flower is held on a pedicel from one to several centimeters long. A pedicel is a stem that attaches a single flower to the inflorescence. Such inflores ...
. The apex of a flowering stem forms a terminal swelling which is called the ''torus'' or receptacle.


Inflorescence

In those species that have more than one flower on an axis, the collective cluster of flowers is termed an ''
inflorescence An inflorescence is a group or cluster of s arranged on a that is composed of a main or a complicated arrangement of branches. , it is the modified part of the of where s are formed. The modifications can involve the length and the nature ...
''. Some inflorescences are composed of many small flowers arranged in a formation that resembles a single flower. The common example of this is most members of the very large composite (Asteraceae) group. A single
daisy
daisy
or
sunflower ''Helianthus'' () 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 classification, vi ...

sunflower
, for example, is not a flower but a flower ''
head Head Sport GmbH is an American-Austrian headquartered in . It owns the American tennis racket brand Head. Head GmbH is a group that includes several previously independent companies, including the original "Head Ski Company" (founded in the in ...
''—an inflorescence composed of numerous flowers (or florets). An inflorescence may include specialized stems and modified leaves known as
bract ''). All the "leaves" in this image are bracts. In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in th ...

bract
s.


Diagrams and formulae

A ''floral formula'' is a way to represent the structure of a flower using specific letters, numbers and symbols, presenting substantial information about the flower in a compact form. It can represent a
taxon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
, usually giving ranges of the numbers of different organs, or particular species. Floral formulae have been developed in the early 19th century and their use has declined since. Prenner ''et al.'' (2010) devised an extension of the existing model to broaden the descriptive capability of the formula. The format of floral formulae differs in different parts of the world, yet they convey the same information. The structure of a flower can also be expressed by the means of ''
floral diagram Floral diagram is a graphic representation of 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). T ...
s''. The use of schematic diagrams can replace long descriptions or complicated drawings as a tool for understanding both floral structure and evolution. Such diagrams may show important features of flowers, including the relative positions of the various organs, including the presence of fusion and symmetry, as well as structural details.


Development

A flower develops on a modified shoot or ''axis'' from a determinate apical
meristem The meristem is a type of tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa du ...
(''determinate'' meaning the axis grows to a set size). It has compressed internodes, bearing structures that in classical plant morphology are interpreted as highly modified
leaves A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...

leaves
. Detailed developmental studies, however, have shown that stamens are often initiated more or less like modified stems (caulomes) that in some cases may even resemble
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