Stamen

from Wikipedia, the free encyclopedia
Flowers of Prunus avium ( sweet cherry ) with a few stamens that surround the central carpel.
Carnegiea gigantea flower with many stamens
Schematic representation of a flower with perigyner perianth (= "medium-sized" ovary):
1 cup shaped flowers ground (receptaculum) of the flower cups or Hypanthium forms
the second sepals (sepals)
3 petals (petals)
4. stamens (stamens)
5. Stamp (Pestle)

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.

Schematic representation of a ditheken anther with a Tetrasporangium:
1. stamen
2. theca
third connective
fourth pollen sack
Schematic representation of an anther (detail):
1. Vascular bundle
2. Epidermis
3. Fiber layer
4. Tapetum
5. Pollen

etymology

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.

construction

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.

Stamen

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.

Anthers

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).

function

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).

Modifications

Staminodes

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.

Under adynamandria , at- , autatrygia , one understands the inability of the male sexual organs of a flower to function or the sterility with its own pollen.

Heterodynamy or pseudo-hybridism : Term for apparently hermaphrodite flowers with unevenly developed (unevenly) to functionless anthers or stigmas.

Nectar leaves

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).

Further modifications

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 ).

In heterostyly , a flower adaptation to make self-pollination more difficult or to prevent, stamens of different lengths appear on the different flowers of a plant species.

The filaments of the stamens can also be conspicuously colored and thus take on a viewing function for the pollinator. Examples are Calliandra , Mimosa (Fabaceae) and Callistemon (Myrtaceae).

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
  • Number:
    • 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)
  • apiculate
  • 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

  • Protruding stamens (exserted)

  • Included stamens

  • Diadelphic stamens

  • Tridelphic stamens

  • Synanthic stamens

Special arrangements

  • 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.

  • Stamen attached to a petal (epipetal)

  • Diplostemone stamens

  • Obdiplostemone stamens

  • Antisepal-alternipetal stamens

  • Antipetal-alternisepal stamens

  • Androphoric and monadelphic stamens

Special forms

  • 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)

  • Two-pair (didymous)

  • Didynamic

  • Tetradynamous

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)

Anthers shape

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).

  • Opening lengthways (longitudinal)

  • Opening across (transverse)

  • Valve-like opening (valvular)

  • Opening porous (porous)

See also

literature

Web links

Commons : stamens  - collection of images, videos and audio files

Individual evidence

  1. ^ Charles E. Bessey: Botanical Notes. In: Science. New Series, Vol. 40, No. 1036, 1914, pp. 678-680, JSTOR 1638988 .
  2. ^ A b C. T. Lewis, C. Short: A Latin Dictionary . Clarendon Press, Oxford 1879, online at Perseus Project , accessed September 9, 2017.
  3. ↑ a b H. G. Liddell, R. Scott: A Greek-English Lexicon . revised and augmented throughout by Sir Henry Stuart Jones. Ninth Edition, Clarendon Press, Oxford 1940, 1996, ISBN 978-0-19-864226-8 (reprint), online at Perseus Project, accessed September 9, 2017.
  4. ↑ E. Klein: A comprehensive etymological dictionary of the English language. 6th edition, One Vol. Edition, Elsevier, Amsterdam 1971, ISBN 978-0-444-40930-0 .
  5. ^ FJ Siebenhaar: Terminological dictionary of the medical sciences. Second edition, Arnoldische Buchhandlung, Leipzig 1850, p. 43, online at hdl.handle.net, accessed on September 9, 2017.
  6. ↑ GAEA Saalfeld: Tensaurus Italograecus. Carl Gerold's Sohn, Vienna 1884, p. 77, archive.org , Hansebooks, 2017, ISBN 978-3-7436-7150-8 (reprint).
  7. ↑ Joachim W. Kadereit, Christian Körner, Benedikt Kost, Uwe Sonnewald: Textbook of botany for universities. 37th edition, p. 153.
  8. ^ PF Yeo: Secondary Pollen Presentation. Springer, 1993, ISBN 978-3-7091-7375-6 (reprint), p. 2 f.
  9. ↑ Pat Willmer: Pollination and Floral Ecology. Princeton University Press, 2011, ISBN 978-0-691-12861-0 , pp. 126, 161, 528 f.
  10. ↑ Zentralblatt für Physiologie. Volume 24, F. Deuticke, 1911, p. 268, online at biodiversitylibrary.org, accessed on October 2, 2017.
  11. ^ Karen L. Wilson, David A. Morrison: Monocots: Systematics and Evolution. CSIRO, 2000, ISBN 0-643-06437-0 , p. 316.
  12. ^ HJ Beentje (Ed.): Flora of Tropical East Africa. Balkema, 2003, ISBN 90-5809-411-1 , pp. 11, 51, 67, 110.
  13. ↑ Louis P. Ronse De Craene: Floral Diagrams. Cambridge University Press, 2010, ISBN 978-0-521-49346-8 , pp. 42 f.
  14. ^ R. Rieger, A. Michaelis: Genetic and cytogenetic dictionary. 2nd edition, Springer, 1958, ISBN 978-3-642-53221-4 , p. 4.
  15. ↑ Karl Linsbauer (Ed.): Short dictionary of botany. 2nd edition, Engelmann, 1917, pp. 68, 71, 304, archive.org .
  16. ↑ Karl Linsbauer, p. 304.
  17. ↑ Urania Plant Kingdom : Higher Plants . tape 2 . Urania-Verlag, Leipzig / Jena / Berlin 1976, p. 336 .
  18. ↑ Irritable Stamens in Biological Sciences at The University of Texas at Austin.
  19. ^ Clemens Schlindwein, Dieter Wittmann: Stamen movements in flowers of Opuntia (Cactaceae) favor oligolectic pollinators. In: Plant Systematics and Evolution. Volume 204, Issue 3-4, 1997, pp. 179-193, doi: 10.1007 / BF00989204 .
  20. ↑ JF Pierer , L. Choulant : Medical real dictionary for hand use ... 1st section, 6th volume: Op – Rev , Lit. Comptoir, 1825, p. 313, limited preview in the Google book search.
  21. ↑ Eleanor Lawrence: Henderson's Dictionary of Biology. Fourteenth Edition, Pearson Education, 2008, ISBN 978-0-321-50579-8 , p. 292.