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Gynoecium

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Flower ofMagnolia×wiesenerishowing the many pistils making up the gynoecium in the middle of the flower
Hippeastrumflowers showing stamens, style and stigma
Hippeastrumstigmasand style
Moss plants with gynoecia, clusters of archegonia at the apex of each shoot.

Gynoecium(/ɡaɪˈniːsi.əm,dʒɪˈniːʃi.əm/;fromAncient Greekγυνή(gunḗ)'woman, female', andοἶκος(oîkos)'house';pl.:gynoecia) is most commonly used as a collective term for the parts of aflowerthat produceovulesand ultimately develop into thefruitandseeds.The gynoecium is the innermostwhorlof a flower; it consists of (one or more)pistilsand is typically surrounded by thepollen-producingreproductive organs,thestamens,collectively called theandroecium.The gynoecium is often referred to as the "female"portion of the flower, although rather than directly producing femalegametes(i.e.egg cells), the gynoecium producesmegaspores,each of which develops into a femalegametophytewhich then produces egg cells.

The term gynoecium is also used by botanists to refer to a cluster ofarchegoniaand any associated modified leaves or stems present on a gametophyte shoot inmosses,liverworts,andhornworts.The corresponding terms for the male parts of those plants are clusters ofantheridiawithin the androecium. Flowers that bear a gynoecium but no stamens are calledpistillateorcarpellate.Flowers lacking a gynoecium are called staminate.

The gynoecium is often referred to as female because it gives rise to female (egg-producing) gametophytes; however, strictly speakingsporophytesdo not have a sex, only gametophytes do.[1]Gynoecium development and arrangement is important in systematic research and identification ofangiosperms,but can be the most challenging of the floral parts to interpret.[2]

Introduction[edit]

Unlike (most)animals,plantsgrow new organs afterembryogenesis,including new roots, leaves, and flowers.[3]In the flowering plants, the gynoecium develops in the central region of the flower as a carpel or in groups of fused carpels.[4]After fertilization, the gynoecium develops into a fruit that provides protection and nutrition for the developing seeds, and often aids in their dispersal.[5]The gynoecium has several specialized tissues.[6]The tissues of the gynoecium develop from genetic and hormonal interactions along three-major axes.[7][8]These tissue arise frommeristemsthat produce cells that differentiate into the different tissues that produce the parts of the gynoecium including the pistil, carpels, ovary, and ovals; the carpel margin meristem (arising from the carpelprimordium) produces theovules,ovary septum, and the transmitting track, and plays a role in fusing the apical margins of carpels.[9]

Pistil[edit]

"Pistil" redirects here. Not to be confused withPistol.
A syncarpous gynoecium in context. The gynoecium (whether composed of a single carpel or multiple "fused" carpels) is typically made up of anovary,style, andstigmaas in the center of the flower.

The gynoecium may consist of one or more separate pistils. A pistil typically consists of an expanded basal portion called anovary,an elongated section called astyleand anapicalstructure called astigmathat receives pollen

  • The ovary (from Latinovum,meaning egg) is the enlarged basal portion which containsplacentas,ridges of tissue bearing one or moreovules(integumentedmegasporangia). The placentas and/or ovule(s) may be born on the gynoecial appendages or less frequently on the floral apex.[10][11][12][13][14]The chamber in which the ovules develop is called alocule(or sometimes cell).
  • The style (from Ancient Greekστῦλος,stylos,meaning a pillar) is a pillar-like stalk through which pollen tubes grow to reach the ovary. Some flowers, such as those ofTulipa,do not have a distinct style, and the stigma sits directly on the ovary. The style is a hollow tube in some plants, such aslilies,or has transmitting tissue through which the pollen tubes grow.[15]
  • The stigma (from Ancient Greekστίγμα,stigma,meaning mark or puncture) is usually found at the tip of the style, the portion of the carpel(s) that receivespollen(malegametophytes). It is commonly sticky or feathery to capture pollen.

The word "pistil" comes fromLatinpistillummeaningpestle.A sterile pistil in a male flower is referred to as apistillode.

Carpels[edit]

The pistils of a flower are considered to be composed of one or morecarpels.[note 1]A carpel is the female reproductive part of the flower—usually composed of the style, and stigma (sometimes having its individual ovary, and sometimes connecting to a shared basal ovary) —and usually interpreted as modified leaves that bear structures calledovules,inside which egg cells ultimately form. A pistil may consist of one carpel (with its ovary, style and stigma); or it may comprise several carpels joined together to form a single ovary, the whole unit called a pistil. The gynoecium may present as one or more uni-carpellate pistils or as one multi-carpellate pistil. (The number of carpels is denoted by terms such astricarpellate(three carpels).)

Carpels are thought to bephylogeneticallyderived from ovule-bearing leaves or leaf homologues (megasporophylls), which evolved to form a closed structure containing the ovules. This structure is typically rolled and fused along the margin.

Although many flowers satisfy the above definition of a carpel, there are also flowers that do not have carpels because in these flowers the ovule(s), although enclosed, are borne directly on the floral apex.[12][17]Therefore, the carpel has been redefined as an appendage that encloses ovule(s) and may or may not bear them.[18][19][20]However, the most unobjectionable definition of the carpel is simply that of an appendage that encloses an ovule or ovules.[21]

Centre of aRanunculus repens(creeping buttercup) showing multiple unfused carpels surrounded by longer stamens
Cross-section through the ovary ofNarcissusshowing multiple connate carpels (a compound pistil) fused along the placental line where the ovules form in each locule
Pistil ofBegonia grandis

Types[edit]

If a gynoecium has a single carpel, it is calledmonocarpous.If a gynoecium has multiple, distinct (free, unfused) carpels, it isapocarpous.If a gynoecium has multiple carpels "fused" into a single structure, it issyncarpous.A syncarpous gynoecium can sometimes appear very much like a monocarpous gynoecium.

Comparison of gynoecium terminology usingcarpelandpistil
Gynoecium composition Carpel
terminology 		Pistilterminology Examples
Single carpel Monocarpous (unicarpellate) gynoecium A pistil (simple) Avocado(Perseasp.), most legumes (Fabaceae)
Multiple distinct ( "unfused" ) carpels Apocarpous (choricarpous) gynoecium Pistils (simple) Strawberry(Fragariasp.),Buttercup(Ranunculussp.)
Multiple connate ( "fused" ) carpels Syncarpous gynoecium A pistil (compound) Tulip(Tulipasp.), most flowers

The degree of connation ( "fusion" ) in a syncarpous gynoecium can vary. The carpels may be "fused" only at their bases, but retain separate styles and stigmas. The carpels may be "fused" entirely, except for retaining separate stigmas. Sometimes (e.g.,Apocynaceae) carpels are fused by their styles or stigmas but possess distinct ovaries. In a syncarpous gynoecium, the "fused" ovaries of the constituent carpels may be referred to collectively as a single compound ovary. It can be a challenge to determine how many carpels fused to form a syncarpous gynoecium. If the styles and stigmas are distinct, they can usually be counted to determine the number of carpels. Within the compound ovary, the carpels may have distinct locules divided by walls calledsepta.If a syncarpous gynoecium has a single style and stigma and a single locule in the ovary, it may be necessary to examine how the ovules are attached. Each carpel will usually have a distinct line of placentation where the ovules are attached.

Pistil development[edit]

Pistils begin as small primordia on a floral apical meristem, forming later than, and closer to the (floral) apex than sepal, petal and stamen primordia.Morphologicalandmolecularstudies of pistil ontogeny reveal that carpels are most likely homologous to leaves.[citation needed]

A carpel has a similar function to amegasporophyll,but typically includes a stigma, and is fused, with ovules enclosed in the enlarged lower portion, the ovary.[22]

In somebasal angiospermlineages,DegeneriaceaeandWinteraceae,a carpel begins as a shallow cup where the ovules develop with laminar placentation, on the upper surface of the carpel. The carpel eventually forms a folded, leaf-like structure, not fully sealed at its margins. No style exists, but a broad stigmatic crest along the margin allows pollen tubes access along the surface and between hairs at the margins.[22]

Two kinds of fusion have been distinguished: postgenital fusion that can be observed during the development of flowers, and congenital fusion that cannot be observed i.e., fusions that occurred during phylogeny. But it is very difficult to distinguish fusion and non-fusion processes in the evolution of flowering plants. Some processes that have been considered congenital (phylogenetic) fusions appear to be non-fusion processes such as, for example, the de novo formation of intercalary growth in a ring zone at or below the base of primordia.[23][24][25]Therefore, "it is now increasingly acknowledged that the term 'fusion,' as applied to phylogeny (as in 'congenital fusion') is ill-advised."[26]

Gynoecium position[edit]

Basal angiosperm groups tend to have carpels arranged spirally around a conical or dome-shapedreceptacle.In later lineages, carpels tend to be inwhorls.

The relationship of the other flower parts to the gynoecium can be an important systematic and taxonomic character. In some flowers, the stamens, petals, and sepals are often said to be "fused" into a "floral tube" orhypanthium.However, as Leins & Erbar (2010) pointed out, "the classical view that the wall of the inferior ovary results from the" congenital "fusion of dorsal carpel flanks and thefloral axisdoes not correspond to the ontogenetic processes that can actually be observed. All that can be seen is an intercalary growth in a broad circular zone that changes the shape of the floral axis (receptacle). "[25]And what happened during evolution is not a phylogenetic fusion but the formation of a unitary intercalary meristem. Evolutionary developmental biology investigates such developmental processes that arise or change during evolution.

If the hypanthium is absent, the flower ishypogynous,and the stamens, petals, and sepals are all attached to the receptacle below the gynoecium. Hypogynous flowers are often referred to as having asuperior ovary.This is the typical arrangement in most flowers.

If the hypanthium is present up to the base of the style(s), the flower isepigynous.In an epigynous flower, the stamens, petals, and sepals are attached to the hypanthium at the top of the ovary or, occasionally, the hypanthium may extend beyond the top of the ovary. Epigynous flowers are often referred to as having aninferior ovary.Plant families with epigynous flowers includeorchids,asters,andevening primroses.

Between these two extremes areperigynousflowers, in which a hypanthium is present, but is either free from the gynoecium (in which case it may appear to be a cup or tube surrounding the gynoecium) or connected partly to the gynoecium (with the stamens, petals, and sepals attached to the hypanthium part of the way up the ovary). Perigynous flowers are often referred to as having ahalf-inferior ovary(or, sometimes,partially inferiororhalf-superior). This arrangement is particularly frequent in therose familyandsaxifrages.

Occasionally, the gynoecium is born on a stalk, called thegynophore,as inIsomeris arborea.

  • Flowers and fruit (capsules) of the ground orchid, Spathoglottis plicata, illustrating an inferior ovary.
    Flowers and fruit (capsules) of the ground orchid,Spathoglottisplicata,illustrating an inferior ovary.
  • Illustration showing longitudinal sections through hypogynous (a), perigynous (b), and epigynous (c) flowers
    Illustration showing longitudinal sections through hypogynous (a), perigynous (b), and epigynous (c) flowers

Placentation[edit]

Main article:Ovule

Within the ovary, each ovule is born by a placenta or arises as a continuation of the floral apex. The placentas often occur in distinct lines called lines ofplacentation.In monocarpous or apocarpous gynoecia, there is typically a single line of placentation in each ovary. In syncarpous gynoecia, the lines of placentation can be regularly spaced along the wall of the ovary (parietal placentation), or near the center of the ovary. In the latter case, separate terms are used depending on whether or not the ovary is divided into separate locules. If the ovary is divided, with the ovules born on a line of placentation at the inner angle of each locule, this isaxile placentation.An ovary withfree central placentation,on the other hand, consists of a single compartment without septae and the ovules are attached to a central column that arises directly from the floral apex (axis). In some cases a single ovule is attached to the bottom or top of the locule (basalorapical placentation,respectively).

The ovule[edit]

Main article:Ovule
Longitudinal section of carpellate flower ofsquashshowing ovary, ovules, stigma, style, and petals

In flowering plants, theovule(from Latinovulummeaning small egg) is a complex structure born inside ovaries. The ovule initially consists of a stalked, integumentedmegasporangium(also called thenucellus). Typically, one cell in the megasporangium undergoesmeiosisresulting in one to four megaspores. These develop into a megagametophyte (often called the embryo sac) within the ovule. The megagametophyte typically develops a small number of cells, including two special cells, an egg cell and a binucleate central cell, which are thegametesinvolved indouble fertilization.The central cell, once fertilized by a sperm cell from the pollen becomes the first cell of theendosperm,and the egg cell once fertilized become thezygotethat develops into theembryo.The gap in the integuments through which the pollen tube enters to deliver sperm to the egg is called themicropyle.The stalk attaching the ovule to the placenta is called the funiculus.

Role of the stigma and style[edit]

Main article:Stigma (botany)

Stigmas can vary from long and slender to globe-shaped to feathery. The stigma is the receptive tip of the carpel(s), which receives pollen atpollinationand on which the pollen graingerminates.The stigma is adapted to catch and trap pollen, either by combining pollen of visiting insects or by various hairs, flaps, or sculpturings.[27]

The style and stigma of the flower are involved in most types ofself incompatibilityreactions. Self-incompatibility, if present, preventsfertilizationby pollen from the same plant or from genetically similar plants, and ensures outcrossing.

The primitive development of carpels, as seen in such groups of plants asTasmanniaandDegeneria,lack styles and the stigmatic surface is produced along the carpels margins.[28]

  • Stigmas and style of Cannabis sativa held in a pair of forceps
    Stigmas and style ofCannabis sativaheld in a pair of forceps
  • Stigma of a Crocus flower.
    Stigma of aCrocusflower.

See also[edit]

Notes[edit]

  1. ^carpel (also carpophyl)—Gr. καρπός (karpós, "fruit" ) + Gr. φύλλον (phúllon, "leaf" ) [L. folium].[16]

References[edit]

  1. ^Judd, W.S.; Campbell, C.S.; Kellogg, E.A.; Stevens, P.F. & Donoghue, M.J. (2007).Plant Systematics: A Phylogenetic Approach(3rd ed.). Sunderland, MA: Sinauer Associates, Inc.ISBN978-0-87893-407-2.
  2. ^Sattler, R. (1974). "A new approach to gynoecial morphology".Phytomorphology.24:22–34.
  3. ^Moubayidin, Laila; Østergaard, Lars (2017-08-01)."Gynoecium formation: an intimate and complicated relationship".Current Opinion in Genetics & Development.45:15–21.doi:10.1016/j.gde.2017.02.005.ISSN0959-437X.PMID28242478.
  4. ^Recent Advances and Challenges on Big Data Analysis in NeuroimagingArchived2023-01-19 at theWayback Machine.Frontiers Media SA; 17 May 2017.ISBN978-2-88945-128-9.p. 158–.
  5. ^Encyclopedia of ReproductionArchived2023-01-19 at theWayback Machine.Elsevier Science; 29 June 2018.ISBN978-0-12-815145-7.p. 2–.
  6. ^Molecular basis of fruit developmentArchived2023-01-19 at theWayback Machine.Frontiers Media SA; 26 March 2014.ISBN978-2-88919-460-5.p. 27–.
  7. ^Peréz-Mesa, Pablo; Ortíz-Ramírez, Clara Inés; González, Favio; Ferrándiz, Cristina; Pabón-Mora, Natalia (2020-02-17)."Expression of gynoecium patterning transcription factors in Aristolochia fimbriata (Aristolochiaceae) and their contribution to gynostemium development".EvoDevo.11(1): 4.doi:10.1186/s13227-020-00149-8.ISSN2041-9139.PMC7027301.PMID32095226.
  8. ^Simonini, Sara; Østergaard, Lars (2019)."Female reproductive organ formation: A multitasking endeavor".Current Topics in Developmental Biology.131:337–371.doi:10.1016/bs.ctdb.2018.10.004.ISBN9780128098042.ISSN1557-8933.PMID30612622.S2CID58606227.Archivedfrom the original on 2023-01-19.Retrieved2020-12-27.
  9. ^Fruit Ripening: From Present Knowledge to Future DevelopmentArchived2023-01-19 at theWayback Machine.Frontiers Media SA; 12 August 2019.ISBN978-2-88945-919-3.p. 155–.
  10. ^Macdonald, A.D. & Sattler, R. (1973). "Floral development ofMyrica galeand the controversy over floral theories ".Canadian Journal of Botany.51(10): 1965–1975.doi:10.1139/b73-251.
  11. ^Sattler, R. (1973).Organogenesis of Flowers: a Photographic Text-Atlas.University of Toronto Press.ISBN978-0-8020-1864-9.
  12. ^abSattler, R. & Lacroix, C. (1988). "Development and evolution of basal cauline placentation:Basella rubra".American Journal of Botany.75(6): 918–927.doi:10.2307/2444012.JSTOR2444012.
  13. ^Sattler, R. & Perlin, L. (1982). "Floral development ofBougainvillea spectabilisWilld.,Boerhaavia diffusaL. andMirabilis jalapaL. (Nyctaginaceae) ".Botanical Journal of the Linnean Society.84(3): 161–182.doi:10.1111/j.1095-8339.1982.tb00532.x.
  14. ^Greyson 1994,p. 130.
  15. ^Esau, K. (1965).Plant Anatomy(2nd ed.). New York: John Wiley & Sons.OCLC263092258.
  16. ^"Carpophyl".The Century Dictionary: The Century dictionary.Century Company. 1914. p. 832.Archivedfrom the original on 2023-01-19.Retrieved2018-02-05.
  17. ^D'Arcy, W.G.; Keating, R.C. (1996).The Anther: Form, Function, and Phylogeny.Cambridge University Press.ISBN9780521480635.Archivedfrom the original on 2023-01-19.Retrieved2015-10-27.
  18. ^Greyson, R. I. 1994. The Development of Flowers. New York/Oxford: Oxford University Press.
  19. ^Leins, P. and Erbar, C. 2010. Flower and Fruit. Stuttgart: Schweizerbart Science Publishers
  20. ^Sattler, R. (2024)."Morpho evo-devo of the gynoecium: heterotopy, redefinition of the carpel, and a topographic appraoch".Plants.13(5): 599.doi:10.3390/plants13050599.PMC10935004.PMID38475445.
  21. ^Sattler, R. (2024)."Morpho evo-devo of the gynoecium: heterotopy, redefinition of the carpel, and a topographic appraoch".Plants.13(5): 599.doi:10.3390/plants13050599.PMC10935004.PMID38475445.
  22. ^abGifford, E.M. & Foster, A.S. (1989).Morphology and Evolution of Vascular Plants (3rd ed.).New York: W.H. Freeman & Co.ISBN978-0-7167-1946-5.
  23. ^Sattler, R. (1978). "'Fusion' and 'continuity' in floral morphology ".Notes from the Royal Botanic Garden Edinburgh.36:397–405.
  24. ^Greyson 1994,p. 67–69, 142–145.
  25. ^abLeins, P. & Erbar, C. (2010).Flower and Fruit.Stuttgart: Schweizerbart Science Publishers.ISBN978-3-510-65261-7.
  26. ^Greyson 1994,p. 142.
  27. ^Blackmore, Stephen & Toothill, Elizabeth (1984).The Penguin Dictionary of Botany.Penguin Books.ISBN978-0-14-051126-0.
  28. ^Armen Takhtajan.Flowering PlantsArchived2023-01-19 at theWayback Machine.Springer Science & Business Media; 6 July 2009.ISBN978-1-4020-9609-9.p. 22–.

Bibliography[edit]

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