Gynoecium
Encyclopedia
Gynoecium is most commonly used as a collective term for all carpels in a flower
. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules. They did this by folding and fusing at their edges to form a chamber in which the ovules develop. In many flowers, several to many carpels are fused into a structure that resembles a single carpel. The term gynoecium is useful because it refers to the ovule producing structure in a flower, whether it is a single carpel, multiple unfused carpels or multiple fused carpels. In a typical flower, the gynoecium is the innermost whorl of structures and is surrounded by the androecium (stamens) and then by the perianth
(all the petals and sepals). In imperfect or incomplete flowers the androecium and perianth, respectively, may be absent. The gynoecium is often referred to as female
because it gives rise to female (egg-producing) gametophytes, however, strictly speaking sporophyte
s do not have sex, only gametophytes do. Flowers that bear a gynoecium but no androecium are called carpellate. Flowers lacking a gynoecium are called staminate.
A gynoecium may consist of a single carpel, multiple distinct (unfused) carpels or multiple connate (fused) carpels. Each carpel typically contains one or more ovules
. During pollination
, pollen
is deposited on the gynoecium (typically on a stigma). Successful germination of pollen and growth of pollen tubes
results in fertilization of ova
. There is typically one ovum in each ovule. After fertilization, ovules develop into seeds
, and the gynoecium forms the pericarp of the associated fruit. 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.
In addition to this use of the term gynoecium in flowering plants, in reference to moss
es, liverworts
and hornwort
s, gynoecium refers to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte
shoot.
Carpels are the building blocks of the gynoecium. Gynoecia (whether composed of a single carpel or multiple fused carpels) typically consist of:
Carpels 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 carpel ontogeny reveal that carpels are most likely homologous to leaves. In some basal angiosperm lineages, for example Degeneria, native to Fiji, carpels begin as a shallow cup and eventually form a folded, leaf-like structure, sealed at its margins by interlocking hairs. No stigma or style exists, but a broad stigmatic crest allows pollen tubes access to two rows of ovules enclosed in the carpel. Carpels, like leaves, generally bear three vascular traces.
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 the attached of the ovules. Each carpel will usually have a distinct line of placentation where the ovules are attached.
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 fused into a "floral tube" or hypanthium.
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 and fused to the gynoecium 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 fused 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.
The ovule (from Latin ovulum meaning small egg) is a complex structure, born inside ovaries of carpels in angiosperms. The ovule initially consists of a stalked, integumented megasporangium. Typically one cell in the megasporangium undergoes meiosis resulting in one to four megaspores. These develop into reduced megagametophytes (often called embryo sacs) within the ovule. Before fertilization, the ovule consists of one or two layers of integuments surrounding the remains of the megasporangium, called the nucellus and an embryo sac, with a small number of cells and nuclei, including one egg cell and two polar nuclei (which will form, together with a sperm cell, the primary endosperm nucleus). 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. Ovules are typically positioned so that the micropyle is facing the point of funiculus attachment, but other positions are found in a variety of plant groups.
by pollen from the same plant or from genetically similar plants, and ensures outcrossing.
Stigmas can vary from long and slender to globe shaped to feathery. The stigma is the receptive tip of the carpel, 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. Stigmas must distinguish and reject the pollen of other species, and in some cases are responsible for self incompatibility.
The style of a pistil is the tube-like portion between the stigma and the ovary. It can be either long or short. In some cases the style is responsible for self incompatibility, causing pollen tubes to fail.
pistillum meaning pestle) is also sometimes used to describe each discrete unit of the gynoecium. A pistil can consist of either a single carpel (in a monocarpous or apocarpous gynoecium), in which case it is called a simple pistil, or of several fused carpels (in a syncarpous gynoecium), in which case it is called a compound pistil.
Flower
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 effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules. They did this by folding and fusing at their edges to form a chamber in which the ovules develop. In many flowers, several to many carpels are fused into a structure that resembles a single carpel. The term gynoecium is useful because it refers to the ovule producing structure in a flower, whether it is a single carpel, multiple unfused carpels or multiple fused carpels. In a typical flower, the gynoecium is the innermost whorl of structures and is surrounded by the androecium (stamens) and then by the perianth
Petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...
(all the petals and sepals). In imperfect or incomplete flowers the androecium and perianth, respectively, may be absent. The gynoecium is often referred to as female
Female
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
because it gives rise to female (egg-producing) gametophytes, however, strictly speaking sporophyte
Sporophyte
All land plants, and some algae, have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte, the generation of a plant or algae that has a double set of chromosomes. A multicellular sporophyte generation or phase is present in the life cycle of all land plants...
s do not have sex, only gametophytes do. Flowers that bear a gynoecium but no androecium are called carpellate. Flowers lacking a gynoecium are called staminate.
A gynoecium may consist of a single carpel, multiple distinct (unfused) carpels or multiple connate (fused) carpels. Each carpel typically contains one or more ovules
Ovule
Ovule means "small egg". 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 megaspore-derived female gametophyte in its center...
. During pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
, pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
is deposited on the gynoecium (typically on a stigma). Successful germination of pollen and growth of pollen tubes
Pollen tube
The pollen tubes is the male gametophyte of seed plants that acts as a conduit to transport the male sperm 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 .After pollination, the pollen tube...
results in fertilization of ova
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
. There is typically one ovum in each ovule. After fertilization, ovules develop into seeds
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
, and the gynoecium forms the pericarp of the associated fruit. 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.
In addition to this use of the term gynoecium in flowering plants, in reference to moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
es, liverworts
Marchantiophyta
The Marchantiophyta are a division of bryophyte plants commonly referred to as hepatics or liverworts. Like other bryophytes, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information....
and hornwort
Hornwort
Hornworts are a group of bryophytes, or non-vascular plants, comprising the division Anthocerotophyta. The common name refers to the elongated horn-like structure, which is the sporophyte. The flattened, green plant body of a hornwort is the gametophyte plant.Hornworts may be found worldwide,...
s, gynoecium refers to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte
Gametophyte
A gametophyte is the haploid, multicellular phase of plants and algae that undergo alternation of generations, with each of its cells containing only a single set of chromosomes....
shoot.
Carpel morphology
- An enlarged basal portion called the ovary (from Latin ovum meaning egg), which contains placentas bearing one or more ovules (integumented megasporangia). The chamber in which the ovules develop is called a locule (or sometimes cell).
- The style (from Ancient Greek stülos meaning a pillar), a pillar-like stalk through which pollen tubes grow to reach the ovary.
- The stigma (from Ancient Greek , stigma meaning mark, or puncture), usually found at the tip of the style, the portion of the carpel that receives pollenPollenPollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
(male gametophyteGametophyteA gametophyte is the haploid, multicellular phase of plants and algae that undergo alternation of generations, with each of its cells containing only a single set of chromosomes....
s). It is commonly sticky or feathery to capture pollen.
Carpels 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
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
and molecular studies of carpel ontogeny reveal that carpels are most likely homologous to leaves. In some basal angiosperm lineages, for example Degeneria, native to Fiji, carpels begin as a shallow cup and eventually form a folded, leaf-like structure, sealed at its margins by interlocking hairs. No stigma or style exists, but a broad stigmatic crest allows pollen tubes access to two rows of ovules enclosed in the carpel. Carpels, like leaves, generally bear three vascular traces.
Types of gynoecia
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.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 the attached of the ovules. Each carpel will usually have a distinct line of placentation where the ovules are attached.
Gynoecium position
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 fused into a "floral tube" or hypanthium.
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 and fused to the gynoecium 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
Orchidaceae
The Orchidaceae, commonly referred to as the orchid family, is a morphologically diverse and widespread family of monocots in the order Asparagales. Along with the Asteraceae, it is one of the two largest families of flowering plants, with between 21,950 and 26,049 currently accepted species,...
, asters
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
, and evening primroses
Onagraceae
Onagraceae, also known as the Willowherb family or Evening Primrose family, are a family of flowering plants. The family includes about 640-650 species of herbs, shrubs, and trees in 20-24 genera...
.
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 fused 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
Rosaceae
Rosaceae are a medium-sized family of flowering plants, including about 2830 species in 95 genera. The name is derived from the type genus Rosa. Among the largest genera are Alchemilla , Sorbus , Crataegus , Cotoneaster , and Rubus...
and saxifrages
Saxifragaceae
Saxifragaceae is a plant family with about 460 known species in 36 genera. In Europe there are 12 genera.The flowers are hermaphroditic and actinomorphic...
.
Occasionally, the gynoecium is born on a stalk, called the gynophore
Gynophore
A gynophore is the stalk of certain flowers which supports the gynoecium , elevating it above the branching points of other floral parts....
, as in Isomeris arborea.
Placentation
Within the ovary, each ovule is born by a placenta. These 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. In some cases a single ovule is attached to the bottom or top of the locule (basal or apical placentation, respectively).The ovule
Micropyle
A micropyle is small opening in the surface of an ovule, through which the pollen tube penetrates, often visible as a small pore in the ripe seed....
. The stalk attaching the ovule to the placenta is called the funiculus. Ovules are typically positioned so that the micropyle is facing the point of funiculus attachment, but other positions are found in a variety of plant groups.
The stigma and style
The style and stigma of the flower are involved in most types of self incompatibility reactions. Self incompatibility, if present, prevents fertilizationFertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...
by pollen from the same plant or from genetically similar plants, and ensures outcrossing.
Stigmas can vary from long and slender to globe shaped to feathery. The stigma is the receptive tip of the carpel, which receives pollen at pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
and on which the pollen grain germinates
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
. The stigma is adapted to catch and trap pollen, either by combining pollen of visiting insects or by various hairs, flaps, or sculpturings. Stigmas must distinguish and reject the pollen of other species, and in some cases are responsible for self incompatibility.
The style of a pistil is the tube-like portion between the stigma and the ovary. It can be either long or short. In some cases the style is responsible for self incompatibility, causing pollen tubes to fail.
Pistils
The word pistil (from LatinLatin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
pistillum meaning pestle) is also sometimes used to describe each discrete unit of the gynoecium. A pistil can consist of either a single carpel (in a monocarpous or apocarpous gynoecium), in which case it is called a simple pistil, or of several fused carpels (in a syncarpous gynoecium), in which case it is called a compound pistil.
| Gynoecium composition | Carpel terminology | Pistil terminology | Examples |
|---|---|---|---|
| Single carpel | Monocarpous (unicarpellate) gynoecium | A pistil (simple) | Avocado Avocado The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel... (Persea sp.), most legumes (Fabaceae Fabaceae The Fabaceae or Leguminosae, commonly known as the legume, pea, or bean family, is a large and economically important family of flowering plants. The group is the third largest land plant family, behind only the Orchidaceae and Asteraceae, with 730 genera and over 19,400 species... ) |
| Multiple distinct (unfused) carpels | Apocarpous (choricarpous) gynoecium | Pistils (simple) | Strawberry Strawberry Fragaria is a genus of flowering plants in the rose family, Rosaceae, commonly known as strawberries for their edible fruits. Although it is commonly thought that strawberries get their name from straw being used as a mulch in cultivating the plants, the etymology of the word is uncertain. There... (Fragaria sp.), buttercup (Ranunculus sp.) |
| Multiple connate (fused) carpels |
Syncarpous gynoecium | A pistil (compound) | Tulip (Tulipa sp.), most flowers |