Gynoecium

Last updated
Flower of Magnolia x wieseneri showing the many pistils making up the gynoecium in the middle of the flower Magnolia wieseneri - labelled gynoecium.jpg
Flower of Magnolia × wieseneri showing the many pistils making up the gynoecium in the middle of the flower
Hippeastrum flowers showing stamens, style and stigma Hippeastrum-1.jpg
Hippeastrum flowers showing stamens, style and stigma
Hippeastrum stigmas and style Amaryllis stigma.jpg
Hippeastrum stigmas and style
Moss plants with gynoecia, clusters of archegonia at the apex of each shoot. Moss flowers.jpg
Moss plants with gynoecia, clusters of archegonia at the apex of each shoot.

Gynoecium ( /ɡˈnsi.əm,ɪˈnʃi.əm/ ; from Ancient Greek γυνή (gunḗ) 'woman, female',and οἶκος (oîkos) 'house') is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) pistils and is typically surrounded by the pollen-producing reproductive organs, the stamens, collectively called the androecium. The gynoecium is often referred to as the "female" portion of the flower, although rather than directly producing female gametes (i.e. egg cells), the gynoecium produces megaspores, each of which develops into a female gametophyte which then produces egg cells.

Contents

The term gynoecium is also used by botanists to refer to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot in mosses, liverworts, and hornworts. The corresponding terms for the male parts of those plants are clusters of antheridia within the androecium. Flowers that bear a gynoecium but no stamens are called pistillate or carpellate. 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 speaking sporophytes do not have a sex, only gametophytes do. [1] Gynoecium development and arrangement is important in systematic research and identification of angiosperms, but can be the most challenging of the floral parts to interpret. [2]

Introduction

Unlike most animals, plants grow new organs after embryogenesis, 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 from meristems that produce cells that differentiation 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 carpel primordium) produces the ovules, ovary septum, and the transmitting track, and plays a role in fusing the apical margins of carpels. [9]

Pistil

A syncarpous gynoecium in context. The gynoecium (whether composed of a single carpel or multiple "fused" carpels) is typically made up of an ovary, style, and stigma as in the center of the flower. Mature flower diagram.svg
A syncarpous gynoecium in context. The gynoecium (whether composed of a single carpel or multiple "fused" carpels) is typically made up of an ovary, style, and stigma as 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 an ovary, an elongated section called a style and an apical structure called a stigma that receives pollen.

The word "pistil" comes from Latin pistillum meaning pestle. A sterile pistil in a male flower is referred to as a pistillode.

Carpels

The pistils of a flower are considered to be composed of one or more carpels . [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 called ovules, 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 as tricarpellate (three carpels).)

Carpels are thought to be phylogenetically derived 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 shoot apex. [12] [17] Different remedies have been suggested for this problem. An easy remedy that applies to most cases is to redefine the carpel as an appendage that encloses ovule(s) and may or may not bear them. [13] [14] [18]

Centre of a Ranunculus repens (creeping buttercup) showing multiple unfused carpels surrounded by longer stamens RanunculusRepens-FoxRoost-Newfoundland - stamens and pistils closeup.jpg
Centre of a Ranunculus repens (creeping buttercup) showing multiple unfused carpels surrounded by longer stamens
Cross-section through the ovary of Narcissus showing multiple connate carpels (a compound pistil) fused along the placental line where the ovules form in each locule Narcis zaadhokken.jpg
Cross-section through the ovary of Narcissus showing multiple connate carpels (a compound pistil) fused along the placental line where the ovules form in each locule
Pistil of Begonia grandis Qiu Hai Tang 20191106164316 05.jpg
Pistil of Begonia grandis

Types

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

Comparison of gynoecium terminology using carpel and pistil
Gynoecium compositionCarpel
terminology
Pistil terminologyExamples
Single carpelMonocarpous (unicarpellate) gynoeciumA pistil (simple) Avocado (Persea sp.), most legumes (Fabaceae)
Multiple distinct ("unfused") carpelsApocarpous (choricarpous) gynoeciumPistils (simple) Strawberry (Fragaria sp.), Buttercup (Ranunculus sp.)
Multiple connate ("fused") carpelsSyncarpous gynoeciumA pistil (compound) Tulip (Tulipa sp.), 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 called septa. 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

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. Morphological and molecular studies of pistil ontogeny reveal that carpels are most likely homologous to leaves.[ citation needed ]

A carpel has a similar function to a megasporophyll, but typically includes a stigma, and is fused, with ovules enclosed in the enlarged lower portion, the ovary. [19]

In some basal angiosperm lineages, Degeneriaceae and Winteraceae, 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. [19]

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. [20] [21] [18] Therefore, "it is now increasingly acknowledged that the term 'fusion,' as applied to phylogeny (as in 'congenital fusion') is ill-advised." [22]

Gynoecium position

Basal angiosperm groups tend to have carpels arranged spirally around a conical or dome-shaped receptacle. In later lineages, carpels tend to be in whorls.

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" or hypanthium . 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 the floral axis does 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)." [18] 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 is hypogynous, and the stamens, petals, and sepals are all attached to the receptacle below the gynoecium. Hypogynous flowers are often referred to as having a superior ovary. This is the typical arrangement in most flowers.

If the hypanthium is present up to the base of the style(s), the flower is epigynous. 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 an inferior ovary. Plant families with epigynous flowers include orchids, asters, and evening primroses.

Between these two extremes are perigynous flowers, 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 a half-inferior ovary (or, sometimes, partially inferior or half-superior). This arrangement is particularly frequent in the rose family and saxifrages.

Occasionally, the gynoecium is born on a stalk, called the gynophore, as in Isomeris arborea.

Placentation

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 of placentation. 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 is axile placentation. An ovary with free 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 (basal or apical placentation, respectively).

The ovule

Longitudinal section of carpellate flower of squash showing ovary, ovules, stigma, style, and petals Femalesquash3747.JPG
Longitudinal section of carpellate flower of squash showing ovary, ovules, stigma, style, and petals

In flowering plants, the ovule (from Latin ovulum meaning small egg) is a complex structure born inside ovaries. The ovule initially consists of a stalked, integumented megasporangium (also called the nucellus). Typically, one cell in the megasporangium undergoes meiosis resulting 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 the gametes involved in double fertilization. The central cell, once fertilized by a sperm cell from the pollen becomes the first cell of the endosperm, and the egg cell once fertilized become the zygote that develops into the embryo. The gap in the integuments through which the pollen tube enters to deliver sperm to the egg is called the micropyle. The stalk attaching the ovule to the placenta is called the funiculus.

Role of the stigma and style

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 at pollination and on which the pollen grain germinates. The stigma is adapted to catch and trap pollen, either by combining pollen of visiting insects or by various hairs, flaps, or sculpturings. [23]

The style and stigma of the flower are involved in most types of self incompatibility reactions. Self-incompatibility, if present, prevents fertilization by 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 as Tasmannia and Degeneria , lack styles and the stigmatic surface is produced along the carpels margins. [24]

See also

Notes

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

Related Research Articles

Fruit Seed-bearing part of a flowering plant

In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.

Stamen Male organ of a flower

The stamen is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium.

Crossosomatales Order of flowering plants

The Crossosomatales are an order, first recognized as such by APG II. They are flowering plants included within the Rosid eudicots.

Pollen tube A tubular structure to conduct male gametes of plants to the female gametes

A pollen tube is a tubular structure produced by the male gametophyte of seed plants when it germinates. Pollen tube elongation is an integral stage in the plant life cycle. The pollen tube acts as a conduit to transport the male gamete cells from the pollen grain—either from the stigma to the ovules at the base of the pistil or directly through ovule tissue in some gymnosperms. In maize, this single cell can grow longer than 12 inches (30 cm) to traverse the length of the pistil.

Ovule Female plant reproductive structure

In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus, and the female gametophyte in its center. The female gametophyte — specifically termed a megagametophyte— is also called the embryo sac in angiosperms. The megagametophyte produces an egg cell for the purpose of fertilization. The ovule is a small structure present in the ovary. It is attached to the placenta by a stalk called a funicle. The funicle provides nourishment to the ovule.

Plant reproductive morphology Study of the physical form and structure (the morphology) of those parts of plants directly or indirectly concerned with sexual reproduction

Plant reproductive morphology is the study of the physical form and structure of those parts of plants directly or indirectly concerned with sexual reproduction.

Stigma (botany) Part of a flower

The stigma is the receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower.

Parnassiaceae Family of flowering plants

Parnassiaceae Gray were a family of flowering plants in the eudicot order Celastrales. The family is not recognized in the APG III system of plant classification. When that system was published in 2009, Parnassiaceae were treated as subfamily Parnassioideae of an expanded family Celastraceae.

Ovary (botany) Flowering plant reproductive part

In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule(s) and is located above or below or at the point of connection with the base of the petals and sepals. The pistil may be made up of one carpel or of several fused carpels, and therefore the ovary can contain part of one carpel or parts of several fused carpels. Above the ovary is the style and the stigma, which is where the pollen lands and germinates to grow down through the style to the ovary, and, for each individual pollen grain, to fertilize one individual ovule. Some wind pollinated flowers have much reduced and modified ovaries.

Double fertilization Complex fertilization mechanism of flowering plants

Double fertilization is a complex fertilization mechanism of flowering plants (angiosperms). This process involves the joining of a female gametophyte with two male gametes (sperm). It begins when a pollen grain adheres to the stigma of the carpel, the female reproductive structure of a flower. The pollen grain then takes in moisture and begins to germinate, forming a pollen tube that extends down toward the ovary through the style. The tip of the pollen tube then enters the ovary and penetrates through the micropyle opening in the ovule. The pollen tube proceeds to release the two sperm in the megagametophyte.

Trochodendraceae Family of flowering plants

Trochodendraceae is the only family of flowering plants in the order Trochodendrales. It comprises two extant genera, each with a single species along with up to five additional extinct genera and a number of extinct species. The living species are native to south east Asia. The two living species both have secondary xylem without vessel elements, which is quite rare in angiosperms. As the vessel-free wood suggests primitiveness, these two species have attracted much taxonomic attention.

<i>Eupomatia</i> Genus of flowering plants

Eupomatia is a genus of three flowering shrub species known to science, of the Australian continent ancient family Eupomatiaceae. The Eupomatiaceae have been recognised by most taxonomists and classified in the plant order Magnoliales. The three species of shrubs or small trees grow naturally in the rainforests and humid eucalypt forests of eastern Australia and New Guinea. The type species Eupomatia laurina was described in 1814 by Robert Brown.

Flower Part of a plant

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants. The biological function of a flower is to facilitate reproduction, usually by providing a mechanism for the union of sperm with eggs. Flowers may facilitate outcrossing resulting from cross-pollination or allow selfing when self-pollination occurs.

Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from either parent. Asexual reproduction produces new individuals without the fusion of gametes. The resulting clonal plants are genetically identical to the parent plant and each other, unless mutations occur.

This page provides a glossary of plant morphology. Botanists and other biologists who study plant morphology use a number of different terms to classify and identify plant organs and parts that can be observed using no more than a handheld magnifying lens. This page provides help in understanding the numerous other pages describing plants by their various taxa. The accompanying page—Plant morphology—provides an overview of the science of the external form of plants. There is also an alphabetical list: Glossary of botanical terms. In contrast, this page deals with botanical terms in a systematic manner, with some illustrations, and organized by plant anatomy and function in plant physiology.

Locule Small cavity or compartment within an organ or part of an organism

A locule or loculus is a small cavity or compartment within an organ or part of an organism.

Tetrachondra is a plant genus and a member of the family Tetrachondraceae. It comprises two species of creeping succulent, perennial, aquatic or semi-aquatic herbaceous plants. Its distribution range is disjunct: one species is endemic to New Zealand while the other one is endemic to southern Patagonia and Tierra del Fuego. These plants bear essential oils.

This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary of leaf morphology. For other related terms, see Glossary of phytopathology and List of Latin and Greek words commonly used in systematic names.

<i>Sida acuta</i> Species of flowering plant

Sida acuta, the common wireweed, is a species of flowering plant in the mallow family, Malvaceae. It is believed to have originated in Central America, but today has a pantropical distribution and is considered a weed in some areas.

Floral formula Floral formula is a means to representation of the structure of a flower using numbers, letters and various symbols, presenting substantial information about the flower in a compact form.

A Floral formula is a notation for representing the structure of particular types of flowers. Such notations use numbers, letters and various symbols to convey significant information in a compact form. They may represent the floral form of a particular species, or may be generalized to characterize higher taxa, usually giving ranges of numbers of organs. Floral formulae are one of the two ways of describing flower structure developed during the 19th century, the other being floral diagrams. The format of floral formulae differs according to the tastes of particular authors and periods, yet they tend to convey the same information.

References

  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. ISBN   978-0-87893-407-2.
  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 . ISSN   0959-437X. PMID   28242478.
  4. Recent Advances and Challenges on Big Data Analysis in Neuroimaging . Frontiers Media SA; 17 May 2017. ISBN   978-2-88945-128-9. p. 158–.
  5. Encyclopedia of Reproduction . Elsevier Science; 29 June 2018. ISBN   978-0-12-815145-7. p. 2–.
  6. Molecular basis of fruit development . Frontiers Media SA; 26 March 2014. ISBN   978-2-88919-460-5. 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 . ISSN   2041-9139. PMC   7027301 . PMID   32095226.
  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. ISBN   9780128098042. ISSN   1557-8933. PMID   30612622. S2CID   58606227.
  9. Fruit Ripening: From Present Knowledge to Future Development . Frontiers Media SA; 12 August 2019. ISBN   978-2-88945-919-3. p. 155–.
  10. Macdonald, A.D. & Sattler, R. (1973). "Floral development of Myrica gale and 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. ISBN   978-0-8020-1864-9.
  12. 1 2 Sattler, 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. JSTOR   2444012.
  13. 1 2 Sattler, R. & Perlin, L. (1982). "Floral development of Bougainvillea spectabilis Willd., Boerhaavia diffusa L. and Mirabilis jalapa L. (Nyctaginaceae)". Botanical Journal of the Linnean Society. 84 (3): 161–182. doi:10.1111/j.1095-8339.1982.tb00532.x.
  14. 1 2 Greyson 1994, p. 130.
  15. Esau, K. (1965). Plant Anatomy (2nd ed.). New York: John Wiley & Sons. OCLC   263092258.
  16. "Carpophyl". The Century Dictionary: The Century dictionary. Century Company. 1914. p. 832.
  17. D'Arcy, W.G.; Keating, R.C. (1996). The Anther: Form, Function, and Phylogeny. Cambridge University Press. ISBN   9780521480635.
  18. 1 2 3 Leins, P. & Erbar, C. (2010). Flower and Fruit. Stuttgart: Schweizerbart Science Publishers. ISBN   978-3-510-65261-7.
  19. 1 2 Gifford, E.M. & Foster, A.S. (1989). Morphology and Evolution of Vascular Plants (3rd ed.). New York: W.H. Freeman & Co. ISBN   978-0-7167-1946-5.
  20. Sattler, R. (1978). "'Fusion' and 'continuity' in floral morphology". Notes of the Royal Botanic Garden, Edinburgh. 36: 397–405.
  21. Greyson 1994, p. 67–69, 142–145.
  22. Greyson 1994, p. 142.
  23. Blackmore, Stephen & Toothill, Elizabeth (1984). The Penguin Dictionary of Botany. Penguin Books. ISBN   978-0-14-051126-0.
  24. Armen Takhtajan. Flowering Plants . Springer Science & Business Media; 6 July 2009. ISBN   978-1-4020-9609-9. p. 22–.

Bibliography