For the Bulgarian physician, seeStamen Grigorov. For the data visualization and cartography studio, seeStamen Design. For the structure in cryptogams, seeAntheridium.
Stamens of aHippeastrum with white filaments and prominent anthers carryingpollen
A stamen typically consists of a stalk called thefilament and ananther which containsmicrosporangia. Most commonly anthers are two-lobed (each lobe is termed alocule) and are attached to the filament either at the base or in the middle area of the anther. The sterile (i.e. nonreproductive) tissue between the lobes is called theconnective, an extension of the filament containing conducting strands. It can be seen as an extension on the dorsal side of the anther. Apollen grain develops from amicrospore in the microsporangium and contains the malegametophyte. The size of anthers differs greatly, from a tiny fraction of a millimeter inWolfia spp up to five inches (13 centimeters) inCanna iridiflora andStrelitzia nicolai.
The stamens in a flower are collectively called theandroecium. The androecium can consist of as few as one-half stamen (i.e. a singlelocule) as inCanna species or as many as 3,482 stamens which have been counted in thesaguaro (Carnegiea gigantea).[2] The androecium in various species of plants forms a great variety of patterns, some of them highly complex.[3][4][5][6] It generally surrounds thegynoecium and is surrounded by theperianth. A few members of the familyTriuridaceae, particularlyLacandonia schismatica andLacandonia brasiliana,[7] along with a few species ofTrithuria (familyHydatellaceae) are exceptional in that their gynoecia surround their androecia.
Hippeastrum flowers showing stamens above the style (with its terminal stigma)Closeup of stamens and pistil ofLilium 'Stargazer'
Stamens, with distal anther attached to the filament stalk, in context of floral anatomy
Depending on the species of plant, some or all of the stamens in a flower may be attached to the petals or to thefloral axis. 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.[13] Extreme cases of stamen fusion occur in some species ofCyclanthera in the familyCucurbitaceae and in sectionCyclanthera of genusPhyllanthus (familyEuphorbiaceae) where the stamens form a ring around the gynoecium, with a single locule.[14] Plants having a single stamen are referred to as "monandrous."
Cross section of aLilium stamen, with four locules surrounded by the tapetum
A typical anther contains four microsporangia. Themicrosporangia 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 thetapetum and initially contains diploid pollen mother cells. These undergo meiosis to formhaploid spores. The spores may remain attached to each other in a tetrad or separate after meiosis. Each microspore then divides mitotically to form an immaturemicrogametophyte called apollen grain.
The pollen is eventually released when the anther forms openings (dehisces). These may consist of longitudinal slits, pores, as in theheath family (Ericaceae), or by valves, as in thebarberry family (Berberidaceae). In some plants, notably members ofOrchidaceae andAsclepiadoideae, the pollen remains in masses calledpollinia, 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 ofangiosperms must be transported to thestigma, the receptive surface of thecarpel, of a compatible flower, for successfulpollination to occur. After arriving, the pollen grain (an immature microgametophyte) typically completes its development. It may grow a pollen tube and undergo mitosis to produce two sperm nuclei.
In the typical flower (that is, in the majority of flowering plant species) each flower has bothcarpels andstamens. 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 calledandroecious. A flower with only carpels is calledgynoecious.
Apistil consists of one or more carpels. A flower with functional stamens but no functional pistil is called astaminate flower, or (inaccurately) a male flower. A flower with a functional pistil but no functional stamens is called apistillate flower, or (inaccurately) a female flower.[15]
diplostemonous: in twowhorls, 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 (seediagram)
Connective
Where the connective is very small, or imperceptible, the anther lobes are close together, and the connective is referred to asdiscrete, e.g.Euphorbia pp.,Adhatoda zeylanica. Where the connective separates the anther lobes, it is calleddivaricate, e.g.Tilia,Justicia gendarussa. The connective may also be a long and stalk-like, crosswise on the filament, this is adistractile connective, e.g.Salvia. The connective may also bear appendages, and is calledappendiculate, e.g.Nerium odorum and some other species ofApocynaceae. InNerium, the appendages are united as a staminal corona.
Filament
A column formed from the fusion of multiple filaments is known as anandrophore. Stamens can beconnate (fused or joined in the same whorl) as follows:
extrorse: antherdehiscence directed away from the centre of the flower. Cf.introrse, directed inwards, andlatrorse towards the side.[17]
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 theAsteraceae). The fused stamens are referred to as asynandrium.
Anther
Anther shapes are variously described by terms such aslinear,rounded,sagittate,sinuous, orreniform.
The anther can be attached to the filament's connective in two ways:[18]
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, usuallyversatile (able to move)
^Charles E. Bessey in SCIENCE Vol. 40 (November 6, 1914) p. 680.
^Sattler, R. 1973.Organogenesis of Flowers. A Photographic Text-Atlas. University of Toronto Press.ISBN0-8020-1864-5.
^Sattler, R. 1988. A dynamic multidimensional approach to floral morphology. In: Leins, P., Tucker, S. C. and Endress, P. (eds)Aspects of Floral Development. J. Cramer, Berlin, pp. 1-6.ISBN3-443-50011-0
^Greyson, R. I. 1994.The Development of Flowers. Oxford University Press.ISBN0-19-506688-X.
^Leins, P. and Erbar, C. 2010.Flower and Fruit. Schweizerbart Science Publishers, Stuttgart.ISBN978-3-510-65261-7.
^abLewis, C.T. & Short, C. (1879).A Latin dictionary founded on Andrews' edition of Freund's Latin dictionary. Oxford: Clarendon Press.
^abcKlein, 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.
^abSaalfeld, 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.
^abcdLiddell, 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.
Weberling, Focko (1992)."1.5 The Androecium".Morphology of Flowers and Inflorescences (trans. Richard J. Pankhurst). CUP Archive. p. 93.ISBN0-521-43832-2. Retrieved8 February 2014.
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