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The stamen ( plural ''stamina'' or ''stamens'') is the pollen-producing
reproductive organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
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 an anther which contains '' microsporangia''. Most commonly anthers are two-lobed and are attached to the filament either at the base or in the middle area of the anther. The sterile tissue between the lobes is called the connective, an extension of the filament containing conducting strands. It can be seen as an extension on the dorsal side of the anther. A pollen grain develops from a microspore in the microsporangium and contains the male gametophyte. The stamens in a flower are collectively called the androecium. The androecium can consist of as few as one-half stamen (i.e. a single locule) as in '' Canna'' species or as many as 3,482 stamens which have been counted in the
saguaro The saguaro (, ) (''Carnegiea gigantea'') is a tree-like cactus species in the monotypic genus ''Carnegiea'' that can grow to be over tall. It is native to the Sonoran Desert in Arizona, the Mexican state of Sonora, and the Whipple Mountains ...
(''Carnegiea gigantea''). The androecium in various species of plants forms a great variety of patterns, some of them highly complex. It generally surrounds the gynoecium and is surrounded by the
perianth The perianth (perigonium, perigon or perigone in monocots) 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 ...
. A few members of the family
Triuridaceae Triuridaceae are a family of tropical and subtropical flowering plants, including nine genera with a total of approximately 55 known species. All members lack chlorophyll and are mycoheterotrophic (obtain food by digesting intracellular fungi, o ...
, particularly ''
Lacandonia schismatica ''Lacandonia schismatica'' is a species of mycoheterotrophic plant in the Triuridaceae (although some taxonomists place the genus in a separate family; the Lacandonaceae.). It is endemic to Lacandon Jungle in the State of Chiapas in southern Mexi ...
'' and '' Lacandonia braziliana'', along with a few species of ''
Trithuria ''Trithuria'' is a genus of small aquatic herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Most of the 12 formally characterised species of ''Trithuria'' are found in Australia, with ...
'' (family
Hydatellaceae Hydatellaceae are a family of small, aquatic flowering plants. The family consists of tiny, relatively simple plants occurring in Australasia and India. It was formerly considered to be related to the grasses and sedges (order Poales), but has b ...
) are exceptional in that their gynoecia surround their androecia.


Etymology

* Stamen is the Latin word meaning "thread" (originally thread of the
warp Warp, warped or warping may refer to: Arts and entertainment Books and comics * WaRP Graphics, an alternative comics publisher * ''Warp'' (First Comics), comic book series published by First Comics based on the play ''Warp!'' * Warp (comics), a ...
, in weaving). * Filament derives from classical Latin
filum The filum terminale ("terminal thread") is a delicate strand of fibrous tissue, about 20 cm in length, proceeding downward from the apex of the conus medullaris. It is one of the modifications of pia mater. It gives longitudinal support to ...
, meaning "thread"Lewis, C.T. & Short, C. (1879). ''A Latin dictionary founded on Andrews' edition of Freund's Latin dictionary.'' Oxford: Clarendon Press. * Anther derives from French anthère,Klein, E. (1971). ''A comprehensive etymological dictionary of the English language. Dealing with the origin of words and their sense development thus illustration the history of civilization and culture.'' Amsterdam: Elsevier Science B.V. from classical Latin anthera, meaning "medicine extracted from the flower"Siebenhaar, F.J. (1850). ''Terminologisches Wörterbuch der medicinischen Wissenschaften.'' (Zweite Auflage). Leipzig: Arnoldische Buchhandlung.Saalfeld, G.A.E.A. (1884). ''Tensaurus Italograecus. Ausführliches historisch-kritisches Wörterbuch der Griechischen Lehn- und Fremdwörter im Lateinischen.'' Wien: Druck und Verlag von Carl Gerold's Sohn, Buchhändler der Kaiserl. Akademie der Wissenschaften. in turn from Ancient Greek ἀνθηρά (), feminine of ἀνθηρός () meaning "flowery",Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie.'' Oxford: Clarendon Press. from
ἄνθος {{wiktionary Antho- is a prefix derived from the Ancient Greek ἄνθος (anthos) meaning “flower”. It is found in words such as : * Anthomania, an obsession with flowers * Anthocyanins, a class of phenolic pigments found in plants * Anthodi ...
() meaning "flower" * Androecium (plural ''androecia'') derives from Ancient Greek ἀνήρ () meaning "man", and οἶκος () meaning "house" or "chamber/room".


Variation in morphology

Depending on the species of plant, some or all of the stamens in a flower may be attached to the petals or to the
floral axis The floral axis (sometimes referred to as the receptacle) is the area of the flower upon which the reproductive organs and other ancillary organs are attached. It is also the point at the center of a floral diagram. Many flowers in division Angios ...
. They also may be free-standing or fused to one another in many different ways, including fusion of some but not all stamens. The filaments may be fused and the anthers free, or the filaments free and the anthers fused. Rather than there being two locules, one locule of a stamen may fail to develop, or alternatively the two locules may merge late in development to give a single locule. Extreme cases of stamen fusion occur in some species of ''
Cyclanthera ''Cyclanthera'' is a genus of flowering plants in the family Cucurbitaceae. The name comes from the fact that some species show extreme cases of stamen fusion forming a ring around the gynoecium, with a single locule A locule (plural locules) ...
'' in the family
Cucurbitaceae The Cucurbitaceae, also called cucurbits or the gourd family, are a plant family consisting of about 965 species in around 95 genera, of which the most important to humans are: *''Cucurbita'' – squash, pumpkin, zucchini, some gourds *'' Lagen ...
and in section ''Cyclanthera'' of genus '' Phyllanthus'' (family Euphorbiaceae) where the stamens form a ring around the gynoecium, with a single locule.


Pollen production

A typical anther contains four microsporangia. The ''microsporangia'' form sacs or pockets (''locules'') in the anther (anther sacs or pollen sacs). The two separate locules on each side of an anther may fuse into a single locule. Each microsporangium is lined with a nutritive tissue layer called the ''tapetum'' and initially contains diploid pollen mother cells. These undergo meiosis to form haploid spores. The spores may remain attached to each other in a tetrad or separate after meiosis. Each microspore then divides mitotically to form an immature
microgametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sex ...
called a
pollen grain Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametoph ...
. The pollen is eventually released when the anther forms openings ( dehisces). These may consist of longitudinal slits, pores, as in the heath family (
Ericaceae The Ericaceae are a family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with c.4250 known species spread across 124 genera, making it th ...
), or by valves, as in the
barberry ''Berberis'' (), commonly known as barberry, is a large genus of deciduous and evergreen shrubs from tall, found throughout temperate and subtropical regions of the world (apart from Australia). Species diversity is greatest in South America an ...
family (
Berberidaceae The Berberidaceae are a family of 18 genera of flowering plants commonly called the barberry family. This family is in the order Ranunculales. The family contains about 700 known species, of which the majority are in ''Berberis''. The species i ...
). In some plants, notably members of Orchidaceae and
Asclepiadoideae The Asclepiadoideae are a subfamily of plants in the family Apocynaceae. Formerly, they were treated as a separate family under the name Asclepiadaceae, e.g. by APG II, and known as the milkweed family. They form a group of perennial herbs, twin ...
, the pollen remains in masses called
pollinia A pollinium (plural pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of mil ...
, which are adapted to attach to particular pollinating agents such as birds or insects. More commonly, mature pollen grains separate and are dispensed by wind or water, pollinating insects, birds or other pollination vectors. Pollen of angiosperms must be transported to the stigma, the receptive surface of the ''
carpel Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils' ...
'', of a compatible flower, for successful pollination to occur. After arriving, the pollen grain (an immature microgametophyte) typically completes its development. It may grow a pollen tube and undergoing mitosis to produce two sperm nuclei.


Sexual reproduction in plants

In the typical flower (that is, in the majority of flowering plant species) each flower has both
carpels Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils' ...
and stamens. In some species, however, the flowers are unisexual with only carpels or stamens. ( monoecious = both types of flowers found on the same plant; dioecious = the two types of flower found only on different plants). A flower with only stamens is called androecious. A flower with only carpels is called gynoecious. A flower having only functional stamens and lacking functional carpels is called a staminate flower, or (inaccurately) male.Encyclopædia Britannica.com
/ref> A plant with only functional
carpel Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils' ...
s is called pistillate, or (inaccurately) female. An abortive or rudimentary stamen is called a staminodium or
staminode In botany, a staminode is an often rudimentary, sterile or abortive stamen, which means that it does not produce pollen.Jackson, Benjamin, Daydon; ''A Glossary of Botanic Terms with their Derivation and Accent''; Published by Gerald Duckworth & C ...
, such as in ''
Scrophularia nodosa ''Scrophularia nodosa'' (also called figwort, woodland figwort, and common figwort) is a perennial herbaceous plant found in temperate regions of the Northern hemisphere except western North America. It grows in moist and cultivated waste ground. ...
''. The
carpels Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils' ...
and stamens of
orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering ...
s are fused into a
column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member. ...
. The top part of the column is formed by the anther, which is covered by an anther cap.


Terminology

;Stamen Stamens can also be adnate (fused or joined from more than one whorl): * epipetalous: adnate to the
corolla Corolla may refer to: *Corolla (botany), the petals of a flower, considered as a unit *Toyota Corolla, an automobile model name *Corolla (headgear) A ''corolla'' is an ancient headdress in the form of a small circlet or crown.tepals (as in many
Liliaceae The lily family, Liliaceae, consists of about 15 genera and 610 species of flowering plants within the order Liliales. They are monocotyledonous, perennial, herbaceous, often bulbous geophytes. Plants in this family have evolved with a fair ...
) They can have different lengths from each other: * didymous: two equal pairs * didynamous: occurring in two pairs, a long pair and a shorter pair * tetradynamous: occurring as a set of six stamens with four long and two shorter ones or respective to the rest of the flower (
perianth The perianth (perigonium, perigon or perigone in monocots) 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 ...
): * exserted: extending beyond the corolla * included: not extending beyond the corolla They may be arranged in one of two different patterns: * spiral; or * whorled: one or more discrete whorls (series) They may be arranged, with respect to the
petals Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corolla''. Petals are usually ...
: * diplostemonous: in two
whorls A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). Whorls in nature File:Photograph and axial plane floral d ...
, the outer alternating with the petals, while the inner is opposite the petals. * haplostemenous: having a single series of stamens, equal in number to the proper number of petals and alternating with them * obdiplostemonous: in two whorls, with twice the number of stamens as petals, the outer opposite the petals, inner opposite the sepals, e.g.
Simaroubaceae The Simaroubaceae are a small, mostly tropical, family in the order Sapindales. In recent decades, it has been subject to much taxonomic debate, with several small families being split off. A molecular phylogeny of the family was published in 200 ...
(''see diagram'') ;Connective Where the connective is very small, or imperceptible, the anther lobes are close together, and the connective is referred to as discrete, e.g. ''
Euphorbia ''Euphorbia'' is a very large and diverse genus of flowering plants, commonly called spurge, in the family Euphorbiaceae. "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to t ...
'' pp., '' Adhatoda zeylanica''. Where the connective separates the anther lobes, it is called divaricate, e.g. '' Tilia'', ''
Justicia gendarussa ''Justicia gendarussa'', commonly known as willow-leaved justicia ( mr, बाकस, , , ; sa, कसनः, , , ),Lapsulis in Creole Seychelles; is a small erect, branched shrub. It has been described as rare and endemic to India, though tho ...
''. The connective may also be a long and stalk-like, crosswise on the filament, this is a distractile connective, e.g. ''
Salvia ''Salvia'' () is the largest genus of plants in the sage family Lamiaceae, with nearly 1000 species of shrubs, herbaceous perennials, and annuals. Within the Lamiaceae, ''Salvia'' is part of the tribe Mentheae within the subfamily Nepetoide ...
''. The connective may also bear appendages, and is called appendiculate, e.g. ''
Nerium odorum ''Nerium oleander'' ( ), most commonly known as oleander or nerium, is a shrub or small tree cultivated worldwide in temperate and subtropical areas as an ornamental and landscaping plant. It is the only species currently classified in the ge ...
'' and some other species of
Apocynaceae Apocynaceae (from ''Apocynum'', Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison Members of the ...
. In ''Nerium'', the appendages are united as a staminal corona. ;Filament A column formed from the fusion of multiple filaments is known as an androphore. Stamens can be connate (fused or joined in the same whorl) as follows: * extrorse: anther dehiscence directed away from the centre of the flower. Cf. introrse, directed inwards, and latrorse towards the side. * monadelphous: fused into a single, compound structure * declinate: curving downwards, then up at the tip (also – declinate-descending) * diadelphous: joined partially into two androecial structures * pentadelphous: joined partially into five androecial structures * synandrous: only the anthers are connate (such as in the
Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...
). The fused stamens are referred to as a synandrium. ;Anther Anther shapes are variously described by terms such as linear, rounded, sagittate, sinuous, or reniform. The anther can be attached to the filament's connective in two ways: * basifixed: attached at its base to the filament ** pseudobasifixed: a somewhat misnomer configuration where connective tissue extends in a tube around the filament tip * dorsifixed: attached at its center to the filament, usually versatile (able to move)


Gallery


References


Bibliography

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External links

{{Authority control Plant anatomy Plant morphology Plant sexuality Plant reproductive system Pollination