The microsphorophyll of the cover-seeded plants is called the stamen ( stamen , plural: stamina ) . It is the pollen- producing organ in hermaphroditic or purely male flowers, the covering plant. A stamen usually consists of a stamen (filament) and the anther sitting on it, which produces the pollen. The totality of all stamens of a flower is called the androeceum . The number of stamens in a flower can vary from one to around 4000, depending on the plant. Adansonia digitata , Annona montana , the Souarin nut tree and Carnegiea gigantea (over 3400) have very many stamens, 1500 and more . Most orchids and for example the Zingiberaceae , on the other hand, only have one stamen. The Marantaceae have only half a fertile stamen.
The botanical name of the stamen, stamen, is derived from the Latin word for warp thread, thread. The stamen is called filament and is derived from the Latin word for thread, filum . The botanical term for the anther , anther, comes from the Latin word anthera for medicinal flower extract from the ancient Greek ἀνθηρά anthira , female from ἀνθηρ antς antheros bloom from ἄνθος anthos flower. Theca derives from Latin theca off from the ancient Greek θήκη counter cover, box, containers of τίθημι tithêmi put, put, put. Androeceum comes from the ancient Greek ἀνήρ aner man, husband and οἶκος oikos house, apartment or room, chamber, space.
The basic structure of the stamen in the Bedecktsamern is relatively stable and is only rarely modified. However, the design of the filament and the anthers can vary in their phenotypic characteristics.
The supporting part of the stamen is the stamen. It usually starts directly on the flower base and can be free-standing, fused with other stamens or fused with the surrounding petal shell. The filament is usually narrow and thread-shaped, but can also be short and stocky. In rare cases it is completely absent.
The upper part of the stamen is the anthers ( anther ). It is usually divided into two halves, the so-called counters (singular: theka ). These are connected by a central tissue with vascular bundles, called connective. A theka usually consists of two fused pollen sacs, which are technically also referred to as loculamente; There are usually four pollen sacs per stamen. The wall of a pollen sac is almost always multi-layered: depending on the plant, an inner wall layer or fiber layer (endothecium) and an outer wall layer (exothecium) appear in addition to the epidermis as an externally closing tissue; one of these layers is rarely missing. As a result of the loss of water in the tissue layers of the exo- or endothecium, their cells tear open at a mostly pre-formed (preformed) point, creating a longitudinal tear in the pollen sac wall through which the pollen is released. The pollen sac wall closes off the inner cavity, the archespora , with a layer of tissue, the tapetum , which is perishable in angiosperms . This plays an important role in nourishing the pollen produced and, through the release of sporopollenin , in the formation of the pollen wall.
In most plants, the anthers are the vertical continuation of the filament. One speaks of a terminal anther. In individual cases, there are a number of modifications to this basic position, some of which have arisen through adaptation to the ecological environmental conditions.
Pseudoanthers can also occur; they are sterile and only serve to attract pollinators and do not offer any nectar or pollen. Also pseudo stamens occur, these are structures which mimic a stamen and partially serve as a substitute for presentation pollen (pollen secondary presentation).
When ripe, the anther opens (mostly in the longitudinal direction) by a cohesion mechanism (different tension conditions when the fiber layer and the epidermis dry out). Dry weather therefore favors the release of pollen. The pollen is finally transferred to the stigma for pollination by wind, insects, etc.
In some species, a distinction is made between two forms of anthers ( heteranthere ; see also under form of anthers); Food and feed anthers (the pollen of which is used by the flower visitors as food) (trophanthers) and fertilization anthers (the pollen is used for fertilization) (gonanthers).
A staminodium (plural staminodes ) is a sterile or stunted stamen that has become sterile through evolutionary reduction (regression). The staminodium is a kind of rudimentary organ of the flower that does not produce any fertile pollen. It can also carry a sterile anther (antherode). With further reduction, the stamen can be completely missing. Using the example of the pharynx (Scrophulariaceae), a regression series can be set up, which can also be found in current textbooks (the latter two genera are, however, now counted among the plantain family according to new molecular biological studies ):
- Mullein ( Verbascum ): five stamens
- Brown root ( Scrophularia ): four stamens and a staminodium
- Thimbles ( digitalis ): four stamens
- Speedwell ( Veronica ): two stamens
There are also pseudostaminodes , these are appendages between the filaments that appear like staminodes, or they come from other structures such as the petals or the flower base.
Heterodynamy or pseudo-hybridism : Term for apparently hermaphrodite flowers with unevenly developed (unevenly) to functionless anthers or stigmas.
Nectar or honey leaves are stamens or petals that produce nectar and thereby attract insects . Nectaries can be present at the base of stamens (filament or stem nectaries) or as appendages. Whole staminodes can also be transformed into nectar leaves (staminodialnectaries).
Often, modifications of stamens and staminodes occur, which indicate a special pollination mechanism . In many species of the mint genus Salvia ( sage ) and in the species Hemigenia eutaxioides two of the four stamens form a joint. This is used to position the pollen more precisely on the body of the pollinator.
In the ginger family there is only one functional stamen, while transformed staminodes take on the function of petals.
Leaf-like appendages can form on the stamens. These are often vividly colored and can simulate a corolla ( secondary corolla ). Such flower transformations are typical of the spawn herb family . Such appendages are also present in the silk plants ( Asclepias ).
Stamens can also respond to various stimuli and perform nastias . Such sensitive , irritable stamens have z. B. those of the genus Berberis , these are seismonastic. Or some kinds of the opuntia have thigmonastic stamens.
Arrangement / forms
The stamens can be arranged in different ways:
- protruding, protruding, going beyond the flower envelope (exserted, phanerantherous)
- included, inserted, cryptantherous
- Defined number (definite): anandrous, unmanly, emasculated (anandrous, astemonous); no stamens, monandrous, monandrous; a stamen, diandrous, two-male (diandrous); two stamens, tri-, tetr-, pent-, hex- (heran-), ... decandrous, ten-male (decandrous); ten stamens
- Undefined number (undefinite, numerous): poly-, multiandrous, poly-, multiandrous; many stamens, oligandrous, almost female (oligandrous); few stamens
If the stamens are different in length and shape, with different shapes, this is called heterandry. Heterantheria is not exactly the same, it is specifically related to the anthers (see also under Anther form), this is often confused.
Filament / stamen
- Carrying stamens, present (filamentous)
- Stamens very short (subsessile)
- Stamens missing, filamentless (absent, afilamentous, sessile)
- one-sided, asymmetrically arranged (unilateral)
- approximated, close together (approxymate)
- Position in relation to the gynoeceum; on the ovary , (hypogynous) (epigyn), center (perigynous) under
- free, unfused; also different (distinct, separate, filantherous) (apostemonous) (normal case)
- unequal length (heterostemonous)
- equal length (homo-, isostemonous)
- uneven, dimorphic (dimorphic)
- unbranched; the stamens are not branched (normal case)
- branched (divergent, branched, ramified, ramose); the stamens are branched
- straight, upright (linear, erect)
- thread-like (filiform)
- flat (laminar)
- tongue-shaped (lingulate)
- leaf-like, petal-like (petalantherous, pentaloid, laminar)
- sinuous, tortuous (flexuous, tortuous, torsive)
- twisted (contorted, twisted)
- bubble-shaped (bulbous, inflated)
- bilateral, bifacial (bifacial)
- two-lipped (bilabiate)
- curved, flexed, declined, flexed (ex-, incurved, inflexed) (declinate, re-, deflexed); curved outwards, inwards
- spurred; the stamens have spores (appendages)
- toothed (dentate)
- pointed (acuminate)
- truant (caudate)
- two-pronged; primary and secondary filament tip
- split (split, partite)
- feathered (pinnate)
- with stipple-like appendages (bracteolate)
- hairy (pubescent)
- feathered (plumose)
- hairless, naked (glabrous)
The filaments and / or anthers can be fused, tufted (synandry, serial intergrowth, cohesion , adhesion ), as stamens ( synandrium ); adelphisch (adelphous, phalange, phalanx), (confluent, adnate, adherent, coalescent, connate, connation, coherent):
- bundled, tufted (fascicle, fasciculate); individual, free stamens, arranged in bundles
- monadelphic, one brother (monadelphous); grown in one piece, all stamens united in a single tubular group (Columna) around the style.
- diadelphic (diadelphous); the filaments united in two parts, two parts
- tridelphic (triadelphous); the filaments united in three parts, three-part ... pentadelphic (pentadelphous) ...; the filaments united in five parts, five parts ...
- polydelphic (polyadelphous); the filaments united in several bundles (more than three)
- synandrium (synandrous); the filaments and anthers are fused
- synantherous (synantherous, syngenesious); only the anthers are fused
- gynandrous (gynandrous, gynosteminal) (female); Filaments stamped, connected or united with the stamp → Gynostemium (Columna)
Gynostegium , scar columns; Growing or sticking of the stamens with the pistil
- inner corona, staminale Nebenkrone , (staminal corona); apical process
- outer corona, interstaminal corona; dorsal process
- epipetal (epipetalous, petalostemonous): attached to the petals, petals
- episepal (episepalous, sepalostemonous); grown on or on the sepals
- epiphilic, -tepal (epiphyllous, epitepalous, tepalostemonous): attached to the perianth, tepals
- spiral (spiral); primary polyandry
- whorled; uni-, bi-, polyseriat
- haplostemon (haplo-, isostemonous): in a single stamen circle, whorls alternating with the petals and arranged in the same number.
- obhaplostemon (obhaplo-, isostemonous): in a single stamen circle, whorls opposite the petals and arranged in the same number.
- diplostemon (diplostemonous): two stamen circles, whorls, of which the outer stamens are above / in front of the sepals (episepal), the inner ones above / in front of the petals (epipetal). With twice as many stamens as petals.
- obdiplostemon (obdiplostemonous): with double, inverted stamen circles, whorls, of which the outer stamens are above / in front of the petals (epipetal), the inner ones above / in front of the sepals (episepal). With twice as many stamens as petals.
- polystemon (polystemanous); more than two stamen circles, whorls; polyseriate
- in patterns or disordered
- Duplication, splitting; secondary polynadry (dédoublement, dedublication, chorisis) centrifugal, -petal
- epi-, anti (e) sepal (epi-, anti-, antesepalous, alternipetalous); opposite the sepals, alternating with the petals
- epi-, anti (e) petal (epi-, anti-, antepetalous, alternisepalous); opposite to the petals, alternating with the sepals
- alterniphil, -tepal (alterniphyllous, alternitepalous); alternating with the tepals
- antiphilic, -tepal (antiphyllous, antitepalous); opposite the tepals
- Petalody ; the transformation of stamens into petals. This process creates the double flowers
- androphoric, columnar; a stalk or a column, which supports the stamens, attached stamens to a slightly raised flower axis shaped as a stamen carrier .
- androgynophore ; stem-like extension of the flower axis, which carries the pistil and stamens
- staminophor (staminal ring); a fabric tape around the tip of the hypanthium in a eucalyptus flower in which the stamens sit.
- two-pair (didymous); two equal pairs
- Dynamie (dynamy); Thickness and difference in shape of the upper and lower stamens
- Didynamie, didynam (isch) (two-power) (didynamy, didynamous); two pairs, one long and one short
- tridynam (isch), (three-power) (tridynamous); three long and three short
- tetradynam (isch) (four powerful) (tetradynamous); four long and two short
- pentadynam (isch) (five-powerful) (pentadynamous); five long and five short
- heterodynam (isch) (heterodynamous); with different lengths (in a whorl)
- homo-, isodynam (isch) (homo-, isodynamous); with equal lengths (in a whorl)
Form of the connective
The connective can be designed in different ways
- branched, two-part, divorced (divergent)
- discreet, very small or absent (discrete)
- diverging, branched (branched, divaricate)
- pulled apart, in the shape of a horseshoe (distractile, elongated); one anthers sterile, one fertile
- elongated (beyond the anther) and (pinnate) (appendicular)
The shape of the anthers can be rounded, linear, oblong, curved, kidney-shaped (reniform), arrow-shaped (sagittate), sinuous (sinuous), with appendiculate, with process, with a hood (hooded), hairy, naked, bearing awns (aristate), lobed (lobed), leaf-like (laminar), X-, H-, S-shaped etc. The counters can also run into one another at the top or at the base or be fused together (confluent, adnate).
In cross-section the anthers can have various shapes; elliptical (oval), egg-shaped (ovoid), arched, convex or concave to the flower axis (arcuate), rectangular (rectangular), trapezoidal (trapezoidal).
The anthers can be only a few tenths of a millimeter to several centimeters long.
If two different types of anthers are present, one speaks of heter (o) antheria (e.g. size, color, function, shape or temporal difference in pollen release); if all anthers are uniform, this is called hom (o) antheria . (See also under function)
Opening of the anthers
The opening ( dehiscence ), (bursting, popping open) (stomium) of the anthers can be done in different ways:
- longitudinal: (one or two) long slits appear in the longitudinal direction of the anthers
- sideways, sideways (lat (e) rorse, lateral): lateral slits
- inwards, jumping upwards (introrse): slits inwards, towards the center of the flower
- outwards, jumping up outwards (extrorse): slits outwards, towards the petals
- transverse (transverse): with central cracks in the anthers, transverse to the longitudinal axis
- valvular, flap-shaped (valvular): the anther wall breaks, is raised like valve flaps to expose the pollen grains
- porous, poricidal: with pores at the tip or base of the anthers
- irregular (irregular): the anther wall breaks irregularly (contracting and squeezing out)
The terms introrse , extrorse , latrorse are not suitable to describe in each case to the direction of the pollen release of floral axis. Because depending on the cross section of the anthers and the bend of the filament, the pollen sacs can open in two different directions. In horizontally oriented flowers or in poricidal anthers, the pollen sacs can also open upwards or downwards (basal, apical, upwards, downwards).
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