stamen
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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 version of the word or phr ...

plural
''stamina'' or ''stamens'') is the
pollen File:Pollen Tube.svg, Pollen Tube Diagram 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 ma ...

pollen
-producing
reproductive organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process by which new in ...
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 function of a flower is to facilitate reproduct ...

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 Microsporangia are sporangia that produce microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants that have Heterospory, heterosporic life cycles, such as Spermatophyte, seed plants, Selagin ...
''. 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 Microspores are land plant spores that develop into male gametophytes, whereas megaspores develop into female gametophytes. The male gametophyte gives rise to sperm cells, which are used for fertilization of an egg cell to form a zygote A ...
in the microsporangium and contains the male
gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, 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 ...
. 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 A locule (plural locules) or loculus (plural loculi) (meaning "little place" in Latin) is a small cavity or compartment within an organ or part of an organism (animal Animals (also called Metazoa) are multicellular eukaryotic organisms th ...
) 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 biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species i ...

saguaro
(''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 '' 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 ...

gynoecium
and is surrounded by the
perianth 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 the non-reproductive part of the flower ...
. A few members of the family
Triuridaceae Triuridaceae are a family of tropical and subtropical flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family ...
, particularly ''
Lacandonia schismatica ''Lacandonia schismatica'' is a species of mycoheterotrophic plant in the Triuridaceae. It is endemic to Lacandon Jungle in the State of Chiapas in southern Mexico. It is known from very few populations and is considered endangered by the research ...
'', are exceptional in that their gynoecia surround their androecia.


Etymology

* Stamen is the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became the ...

Latin
word meaning "thread" (originally thread of the warp, in weaving). * Filament derives from
classical Latin Classical Latin is the form of Latin, Latin language recognized as a Literary language, literary standard language, standard by writers of the late Roman Republic and early Roman Empire. It was used from 75 BC to the 3rd century AD, when it deve ...
filum The filum terminale ("terminal thread") is a delicate strand of connective tissue, 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 longitud ...
, 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 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 into the following periods: Mycenaean Greek (), Dark Ages () ...
wikt:ἀνθηρά, ἀνθηρά (), feminine of wikt:ἀνθηρός, 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 wikt:ἄνθος, ἄνθος () meaning "flower" * Androecium (plural ''androecia'') derives 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 into the following periods: Mycenaean Greek (), Dark Ages () ...
wikt:ἀνήρ, ἀνήρ () meaning "man", and wikt:οἶκος, 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. 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'' in the family Cucurbitaceae 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 Gametophyte, microgametophyte called a Pollen, pollen grain. The pollen is eventually released when the anther forms openings (dehiscence (botany)#Anther dehiscence, dehisces). These may consist of longitudinal slits, pores, as in the Erica (plant), heath family (Ericaceae), or by valves, as in the barberry family (Berberidaceae). In some plants, notably members of Orchidaceae and Asclepiadoideae, the pollen remains in masses called Pollinium, pollinia, 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 (botany), stigma, the receptive surface of the ''Gynoecium, carpel'', 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 Gynoecium, carpels 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 carpels is called pistillate, or (inaccurately) female. An abortive or rudimentary stamen is called a staminodium or staminode, such as in ''Scrophularia, Scrophularia nodosa''. The Gynoecium, carpels and stamens of orchids are fused into a column (botany), column. 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 (flower), corolla * epiphyllous: adnate to undifferentiated tepals (as in many Liliaceae) 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 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 the non-reproductive part of the flower ...
): * 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: * diplostemonous: in two Whorl (botany), whorls, 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 (''see #Obdiplostemony, 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'' pp., ''Adhatoda zeylanica''. Where the connective separates the anther lobes, it is called divaricate, e.g. ''Tilia'', ''Justicia gendarussa''. The connective may also be a long and stalk-like, crosswise on the filament, this is a distractile connective, e.g. ''Salvia''. The connective may also bear appendages, and is called appendiculate, e.g. ''Nerium odorum'' and some other species of Apocynaceae. 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 (botany), 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 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