Gynoecium

xiang is most commonly used as a collective term for the parts of a flower thatproduce the ovule and eventually Develops into fruits and seeds . Gynoecium is the innermost whorl of a flower ; It has (one or more) pistils and is usually surrounded by the pollen-producing reproductive organs , the stamens , which are collectively called the androecium .is called. The zygote is often referred to as the ” female part of the flower”, although rather than directly producing gametes (i.e. egg cells ), the zygote produces megaspores , each of which develops into a female gametophyte which then produces egg cells . Production of.

The term gynoecium is also used by botanists to refer to a group of archegonia and any associated modifying or shoots present on any gametophyte in moss , liverworts , and hornworts . Related terms for the male parts of those plants are the groups of antheridia within the androecium . Flowers that bear a xiphoid but no stamens are called pistillate or carpellate . A flower lacking a zygote is called a staminate .

Gynoecium is often referred to as female because it gives rise to female (egg-producing) gametophytes ; However, strictly speaking sporophytes do not have sex, only gametophytes do. [1] The evolution and arrangement of gynoecium is important in the systematic research and identification of angiosperms, but the floral parts may be the most challenging to interpret.

Introduction

Unlike most animals, plants develop new organs after embryogenesis , including new roots, leaves, and flowers. [3] In flowering plants, the gynoecium develops as a single carpel in the central region of the flower or in clusters of fused carpels. [4] After fertilization, the gynoecium develops into a fruit that provides protection and nutrition to the developing seeds, and often aids in their dispersal. [5] The gynoecium consists of several specialized tissues. [6] The tissues of the gynoecium develop through genetic and hormonal interactions along the three major axes. [7] [8] The meristems arise from the research tissue.that produce cells that differentiate into the various tissues that produce parts of the gynoecium, including the pistil, carpal, ovary, and ovule; The carpel margin produces the meristem (carpal primordia ) ovoid, the ovary septum, the transmitting track, and plays a role in fusing the apical margin of the carpel. [9]

Flower-vagina

The gynoecium may consist of one or more individual pistils. A pistil usually consists of an elongated basal part called the ovary, an elongated segment called a style, and an apical structure that receives pollen called a stigma.

• The ovary (from Latin ovum meaning egg), is the enlarged basal part containing the placentas , ridges of tissue that form one or more ovules (integumentary megasporangia). The placenta and/or ovum may be born on the gynecological appendages or, less often, on the flower head. ^{[10] [11] [12] [13] [14]} The cell in which the egg develops is called a space (or sometimes a cell).
• The style (from Ancient Greek , stylos meaning a column), is a column-like stalk through which pollen tubes grow to reach the ovary. Some flowers, such as the tulipa , do not have a distinct style, and the stigma sits directly on the ovary. Some plants, such as style lilies, have a hollow tube, or contain transmitting tissue, through which pollen tubes develop. ^[15]
• The stigma (from Ancient Greek μα , stigma meaning mark, or puncture), is usually found at the tip of the styl, the part of the carpel that receives pollen (male gametophytes). It is usually sticky or feathery to hold pollen.

The word “pistil” comes from the Latin pistilum which means pestle. A male flower has a sterile pistil known as a pistillode .

Carapace

The pistil of a flower is considered to be composed of one or more carpels . ^{[note 1]} A carpel is the female reproductive part of the flower – composed of the ovary, style and stigma – and is usually interpreted as modified leaves called ovules, inside which egg cells eventually form. A pistil may have a carpel (with its ovary, style and stigma); Or it may consist of several carpels to form an ovary, the whole unit called a pistil. The gynoecium may present as one or more uni-carpellet pistils or as a multi-carpellet pistil. (The number of carpels is denoted by words such as tricarpelate (three carpels).)

The carapace is thought to be derived from phylogenetically spore-bearing leaves or leaf homologues (megasporophylls), which evolved to form a closed structure containing the spores. This structure is usually rolled and attached with a margin.

Although many flowers meet the above definition of a carpel, there are also flowers that do not have carpels because the ovules in these flowers, although attached, are borne directly at the shoot apex. ^[12] [17] Various solutions have been suggested for this problem. A simple solution that applies to most cases is to redefine the carpel as an appendage that surrounds the ovum and may or may not bear them.

Type

If a gynoecium consists of a single carpel, it is called a monocarpus . If a gynoecium has many, distinct (free, unused ) carpels, it is apocarpus . If a gynoecium has several carpels “fused” into a single structure, it is called syncarpus . A syncarpus gynoecium can sometimes appear like a monocarpus gynoecium.

The degree of fusion (“fusion”) in a syncytial gynoecium may vary. The carpels may be “fused” only at their bases, but retain distinct styles and stigmas. In addition to maintaining separate stigmas, the carpels can become completely “fused”. Sometimes (for example, in Apocynaceae) the carpels are attached to their own style or stigma but have separate ovaries. In a syncarpus gynoecium, the “fused” ovary of the constituent carpels may be referred to collectively as a single compound ovary. It can be a challenge to determine how many carpels are fused to form a syncarpus gynoecium. If the styles and stigmas are different, they can usually be counted to determine the number of carpels. Within the mixed ovary, the septa in the carpelThere may be separate spaces divided by walls called. If the ovary of a Syncarpus gynoecium has the same style and stigma and the same location, it may be necessary to examine how the ovules are attached. Each carpel usually has a separate line of placentation where the ovules are attached.

Stamens development

The pistils begin as small primordia on the apical meristem, which form later, and the sepals, petals and stamens are closer to the (floral) apex than the primordia. Morphological and molecular studies of pistils ontogeny suggest that the carpels are most likely to be homologous to the leaves. ^{[ citation needed ]}

A carpel has a similar function to a megasporophyll, but usually includes a stigma, and is fused, with the ovary, attached in the lower part of the enlarged spore.

In some basal angiosperm lineages, Degeneriaceae and Winteraceae, a carpel begins as a shallow cup where ovules develop with laminar placentation on the upper surface of the carpel. The carpel eventually forms a folded, leaf-like structure, its margins are not completely sealed. No style is present, but a broad stigmatic crest along the margin allows pollen tubes to reach along the surface and between hairs at the margins. ^[19]

Two types of fusions have been distinguished: postgenital fusions that can be observed during flower development, and congenital fusions that cannot be observed, that is, fusions that occur during phylogeny. But it is very difficult to differentiate between fusion and non-fusion processes in the development of flowering plants. Some processes that are considered congenital (phylogenetic) fusions appear to be non-fusion processes, for example, the de novo formation of intercalary growth at the base of the primordia or in a ring zone below it. ^{[20] [21] [18]} Therefore, “it is now increasingly accepted that the term ‘fusion’, as applied to phylogeny (as in ‘congenital fusion’) is inappropriate.” ^[22]

Gynoecium position

Basal angiosperm clusters have carpels arranged spirally around a conical or dome-shaped vessel. In later lineages, the carpels are in whorls.

The relation of other flower parts to the gynoecium may have an important systematic and taxonomic character. In some flowers, the stamens, petals and sepals are often called “flower tubules” or “fused” in the hypanthium . However, as Leins and Erbar (2010) pointed out, “the classical view that the inferior ovary wall arises from an “innate” fusion of the dorsal carpel flanks and the floral axis does not correspond to ontogenetic processes that can actually be observed. .. All that can be observed is an interacting growth in a broad circular region that changes the shape of the flower axis (eclipse).” ^[18]And what happened during evolution is not a phylogenetic fusion but the formation of a unitary intercalary meristem. Evolutionary Developmental biology examines the developmental processes that arise or change during development.

If the hypanthium is absent, the flower is hypogynous , and the stamens, petals and sepals are all attached to the underside of 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, the flower is epigynous . In an epigynous flower, the stamens, petals and sepals are attached to the hypanthium at the apex of the ovary or, occasionally, the hypanthium may extend beyond the apex of the ovary. Epiginous flowers are often referred to as the inferior ovary . The families of epigynous flowering plants include orchids, asters, and evening primroses.

Between these two extremities are perigynous flowers, in which a hypanthium is present, but either free of the gynoecium (in which case it may appear to be a cup or tube surrounding the gynoecium ) or partially gynoecium (stamens). with) petals, and sepals are attached to the hypanthium part above the ovary). Perigynous flowers are often referred to as half-inferior ovaries (or, occasionally, partially inferior or half-superior ). This arrangement is particularly frequent in the rose family and saxifrage.

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

• Flowers and fruits (capsule) of the ground orchid, Spathoglottis plicata , showing an inferior ovary.

Umbilical cord

Within the ovary, each ovule is produced by the placenta or as a continuation of the flower head. The placentas often lie in separate lines called lines of placentation. In monocarpus or apocarpus gynosia, there is usually one row of placenta in each ovary. In syncopal gynosia, the lines of placenta may be located regularly along the wall of the ovary ( parietal placentation ) or near the center of the ovary. In the latter case, different terms are used depending on whether the ovary has been divided into different locations. The ovary is divided, with spores attached to a row of umbilical cord at the inner angle of each locule, so it is the axile umbilical cord . On the other hand, for free central placentationWith an ovary there is a single compartment without septa 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 below or above the location ( basal or apical placentation , respectively ).

Oval

Longitudinal section of carpellet flower of squash showing ovary, ovule, stigma, style and petals

In flowering plants, the ovule (from Latin ovulum meaning small egg) is a complex structure borne inside the ovary. The ovule initially consists of a stalked, fully megasporangium (called nucellus).Also called). Typically, a cell in the megasporangium undergoes meiosis resulting in one to four megaspores. These develop into a megagametophyte (often called an embryo sac) within the ovum. The megagametophyte typically develops a small number of cells, including two specialized cells, an egg cell and a binucleated 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 becomes the zygote that develops into the embryo. The gap in the integument through which the pollen tube enters to deliver the sperm to the egg is called the micropyle. The stalk connecting the ovule to the placenta is called the funiculus.

The role of stigma and style

The stigmas can vary from long and slender to globe-shaped to feathery. Stigma is the receptive end of the carpel, which receives pollen at the time of pollination and on which pollen grains germinate. The stigma is adapted to capture and trap pollen, either by mixing the pollen of incoming insects or by various hairs, flaps, or scutes. ^[23]

Flower style and stigma are involved in most types of self-incompatibility reactions. Self-incompatibility, if present, prevents fertilization by pollen from the same plant or genetically identical plants, and ensures outcrossing.

The primitive development of the carpel, as seen in such plant groups as Tasmania and Degeneria , lacks styles and produces a stigmatic surface along the carpel margin. ^[24]

• The stigma and style of Cannabis sativa held in a pair of forceps
• Stigma of a crocus flower.