A flower, also known as a bloom or blossom, is the reproductive structure found in
gametes. The male gametophytes, which produce sperm, are enclosed within pollen grains produced in the anthers. The female gametophytes are contained within the ovules produced in the carpels
.
Most flowering plants depend on animals, such as
co-evolved with pollinators to be mutually dependent on services they provide to one another—in the plant's case, a means of reproduction; in the pollinator's case, a source of food.[2]
When
carpel mature at the same time, and are positioned so that the pollen can land on the flower's stigma. This pollination does not require an investment from the plant to provide nectar and pollen as food for pollinators.[3] Some flowers produce diaspores without fertilization (parthenocarpy). After fertilization, the ovary of the flower develops into fruit containing seeds
.
Flowers have long been appreciated by humans for their beauty and pleasant scents, and also hold cultural significance as religious, ritual, or symbolic objects, or sources of medicine and food.
Etymology
Flower is from the Middle Englishflour, which referred to both the ground grain and the reproductive structure in plants, before splitting off in the 17th century. It comes originally from the Latin name of the Italian goddess of flowers, Flora. The early word for flower in English was blossom,[4] though it now refers to flowers only of fruit trees.[5]
stipules. Sepals are often waxy and tough, and grow quickly to protect the flower as it develops.[9][10] They may be deciduous, but will more commonly grow on to assist in fruit dispersal. If the calyx is fused together it is called gamosepalous.[9]
Corolla
The petals, together the corolla, are almost or completely fiberless leaf-like structures that form the innermost whorl of the perianth. They are often delicate and thin, and are usually coloured, shaped, or scented to encourage pollination.[11] Although similar to leaves in shape, they are more comparable to stamens in that they form almost simultaneously with one another, but their subsequent growth is delayed. If the corolla is fused together it is called sympetalous.[12]
androecium, or stamens, is the whorl of pollen-producing male parts. Stamens consist typically of an anther, made up of four pollen sacs arranged in two thecae, connected to a filament, or stalk. The anther contains microsporocytes which become pollen, the male gametophyte, after undergoing meiosis. Although they exhibit the widest variation among floral organs, the androecium is usually confined just to one whorl and to two whorls only in rare cases. Stamens range in number, size, shape, orientation, and in their point of connection to the flower.[11][12]
In general, there is only one type of stamen, but there are plant species where the flowers have two types; a "normal" one and one with anthers that produce sterile pollen meant to attract pollinators.[13]
Gynoecium
The gynoecium, or the carpels, is the female part of the flower found on the innermost whorl. Each carpel consists of a stigma, which receives pollen, a style, which acts as a stalk, and an ovary, which contains the ovules. Carpels may occur in one to several whorls, and when fused are often described as a pistil. Inside the ovary, the ovules are attached to the placenta by structures called funiculi.[14][15]
Variation
Although this arrangement is considered "typical", plant species show a wide variation in floral structure.
Peonies and Roses are mostly petaloid stamens.[18]
Many flowers have
zygomorphic. If, in rare cases, they have no symmetry at all they are called asymmetric.[19][20]
Flowers may be directly attached to the plant at their base (sessile—the supporting stalk or stem is highly reduced or absent).[21] The stem or stalk subtending a flower, or an inflorescence of flowers, is called a peduncle. If a peduncle supports more than one flower, the stems connecting each flower to the main axis are called pedicels.[22] The apex of a flowering stem forms a terminal swelling which is called the torus or receptacle.[20]
In the majority of species, individual flowers have both
nectaries, which are glands that produce a sugary fluid used to attract pollinators. They are not considered as an organ on their own.[24]
Following the pollination of a flower, fertilization, and finally the development of a seed and fruit, a mechanism is typically used to disperse the fruit away from the plant.[91] In Angiosperms (flowering plants) seeds are dispersed away from the plant so as to not force competition between the mother and the daughter plants,[92] as well as to enable the colonisation of new areas. They are often divided into two categories, though many plants fall in between or in one or more of these:[93]
Allochory
In allochory, plants use an external vector, or carrier, to transport their seeds away from them. These can be either biotic (living), such as by birds and ants, or abiotic (non-living), such as by the wind or water.[93][94][95]
Many plants use biotic vectors to disperse their seeds away from them. This method falls under the umbrella term Zoochory, while
pulp, an aril, and sometimes an elaiosome (primarily for ants), which are other fleshy structures.[100]
Epizoochory occurs in plants whose seeds are adapted to cling on to animals and be dispersed that way, such as many species in the genus Acaena.[101] Typically these plants seed's have hooks or a viscous surface to easier grip to animals, which include birds and animals with fur. Some plants use mimesis, or imitation, to trick animals into dispersing the seeds and these often have specially adapted colors.[100][102]
The final type of Zoochory is called Synzoochory, which involves neither the digestion of the seeds, nor the unintentional carrying of the seed on the body, but the deliberate carrying of the seeds by the animals. This is usually in the mouth or beak of the animal (called Stomatochory), which is what is used for many birds and all ants.[103]
In abiotic dispersal plants use the vectors of the wind, water, or a mechanism of their own to transport their seeds away from them.
Anemochory involves using the wind as a vector to disperse plant's seeds. Because these seeds have to travel in the wind they are almost always small - sometimes even dust-like, have a high surface-area-to-volume ratio, and are produced in a large number - sometimes up to a million. Plants such as tumbleweeds
detach the entire shoot to let the seeds roll away with the wind. Another common adaptation are wings, plumes or balloon like structures that let the seeds stay in the air for longer and hence travel farther.
In
Hydrochory plants are adapted to disperse their seeds through bodies of water and so typically are buoyant and have a low relative density with regards to the water. Commonly seeds are adapted morphologically with hydrophobic surfaces, small size, hairs, slime, oil, and sometimes air spaces within the seeds.[100] These plants fall into three categories: ones where seeds are dispersed on the surface of water currents, under the surface of water currents, and by rain landing on a plant.[104]
Autochory
Main article:
Autochory
In
autochory, plants create their own vectors to transport the seeds away from them. Adaptations for this usually involve the fruits exploding and forcing the seeds away ballistically, such as in Hura crepitans,[105] or sometimes in the creation of creeping diaspores.[100] Because of the relatively small distances that these methods can disperse their seeds, they are often paired with an external vector.[102]
While land plants have existed for about 425 million years, the first ones
reproduced by a simple adaptation of their aquatic counterparts: spores. In the sea, plants—and some animals—can simply scatter out genetic clones of themselves to float away and grow elsewhere. This is how early plants reproduced. But plants soon evolved methods of protecting these copies to deal with drying out and other damage which is even more likely on land than in the sea. The protection became the seed, though it had not yet evolved the flower. Early seed-bearing plants include the ginkgo and conifers
.
Archaefructus liaoningensis, one of the earliest known flowering plants
Several groups of extinct
seed ferns, have been proposed as the ancestors of flowering plants but there is no continuous fossil evidence showing exactly how flowers evolved. The apparently sudden appearance of relatively modern flowers in the fossil record posed such a problem for the theory of evolution that it was called an "abominable mystery" by Charles Darwin
.
Recently discovered angiosperm fossils such as Archaefructus, along with further discoveries of fossil gymnosperms, suggest how angiosperm characteristics may have been acquired in a series of steps. An early fossil of a flowering plant,
Montsechia vidalii, discovered in Spain) was claimed to be 130 million years old.[108] In 2018, scientists reported that the earliest flowers began about 180 million years ago.[109]
Amborella trichopoda may have characteristic features of the earliest flowering plants
Recent
molecular systematics)[110] shows that Amborella trichopoda, found on the Pacific island of New Caledonia, is the only species in the sister group to the rest of the flowering plants, and morphological studies suggest that it has features which may have been characteristic of the earliest flowering plants.[111]
Besides the hard proof of flowers in or shortly before the Cretaceous,[112][113] there is some circumstantial evidence of flowers as much as 250 million years ago. A chemical used by plants to defend their flowers, oleanane, has been detected in fossil plants that old, including gigantopterids,[114] which evolved at that time and bear many of the traits of modern, flowering plants, though they are not known to be flowering plants themselves, because only their stems and prickles have been found preserved in detail; one of the earliest examples of petrification.
The similarity in
ovary
(female part). As flowers grew more advanced, some variations developed parts fused together, with a much more specific number and design, and with either specific sexes per flower or plant, or at least "ovary inferior".
The general assumption is that the function of flowers, from the start, was to involve animals in the reproduction process. Pollen can be scattered without bright colors and obvious shapes, which would therefore be a liability, using the plant's resources, unless they provide some other benefit. One proposed reason for the sudden, fully developed appearance of flowers is that they evolved in an isolated setting like an island, or chain of islands, where the plants bearing them were able to develop a highly specialized relationship with some specific animal (a wasp, for example), the way many island species develop today. This symbiotic relationship, with a hypothetical wasp bearing pollen from one plant to another much the way
Island genetics is believed to be a common source of speciation
, especially when it comes to radical adaptations which seem to have required inferior transitional forms. Note that the wasp example is not incidental; bees, apparently evolved specifically for symbiotic plant relationships, are descended from wasps.
Likewise, most fruit used in plant reproduction comes from the enlargement of parts of the flower. This fruit is frequently a tool which depends upon animals wishing to eat it, and thus scattering the seeds it contains.
While many such
symbiotic relationships
remain too fragile to survive competition with mainland organisms, flowers proved to be an unusually effective means of production, spreading (whatever their actual origin) to become the dominant form of land plant life.
Flower evolution continues to the present day; modern flowers have been so profoundly influenced by humans that many of them cannot be pollinated in nature. Many modern, domesticated flowers used to be simple weeds, which only sprouted when the ground was disturbed. Some of them tended to grow with human crops, and the prettiest did not get plucked because of their beauty, developing a dependence upon and special adaptation to human affection.[116]
Colour
See also:
Color garden
Reflectance spectra for the flowers of several varieties of rose. A red rose absorbs about 99.7% of light across a broad area below the red wavelengths of the spectrum, leading to an exceptionally pure red. A yellow rose will reflect about 5% of blue light, producing an unsaturated yellow (a yellow with a degree of white in it).
Carl Linnaeus's method for classifying plants focused solely on the structure and nature of the flowers.[117]
In plant taxonomy, which is the study of the classification and identification of plants, the morphology of plant's flowers are used extensively – and have been for thousands of years. Although the history of plant taxonomy extends back to at least around 300 B.C. with the writings of Theophrastus,[118] the foundation of the modern science is based on works in the 18th and 19th centuries.[119]
Carl Linnaeus (1707–1778), was a Swedish botanist who spent most of his working life as a professor of natural history. His landmark 1757 book Species Plantarum lays out his system of classification as well as the concept of binomial nomenclature, the latter of which is still used around the world today.[119][note 1] He identified 24 classes, based mainly on the number, length and union of the stamens. The first ten classes follow the number of stamens directly (Octandria have 8 stamens etc.),[117] while class eleven has 11–20 stamens and classes twelve and thirteen have 20 stamens; differing only in their point of attachment. The next five classes deal with the length of the stamens and the final five with the nature of the reproductive capability of the plant; where the stamen grows; and if the flower is concealed or exists at all (such as in ferns). This method of classification, despite being artificial,[117] was used extensively for the following seven decades, before being replaced by the system of another botanist.[120]
Antoine Laurent de Jussieu (1748–1836) was a French botanist whose 1787 work Genera plantarum: secundum ordines naturales disposita set out a new method for classifying plants; based instead on natural characteristics. Plants were divided by the number, if any, of cotyledons, and the location of the stamens.[120] The next most major system of classification came in the late 19th century from the botanists Joseph Dalton Hooker (1817–1911) and George Bentham (1800–1884). They built on the earlier works of de Jussieu and Augustin Pyramus de Candolle and devised a system which is still used in many of the world's herbaria. Plants were divided at the highest level by the number of cotyledons and the nature of the flowers, before falling into orders (families), genera, and species. This system of classification was published in their Genera plantarum in three volumes between 1862 and 1883.[121] It is the most highly regarded and deemed the "best system of classification," in some settings.[122]
Following the development in scientific thought after Darwin's
cytology, and palynology has become increasingly common. Despite this, morphological characteristics such as the nature of the flower and inflorescence still make up the bedrock of plant taxonomy.[122][123]
Red roses are given as a symbol of love, beauty, and passion.[125]
Poppies are a symbol of consolation in time of death. In the United Kingdom, New Zealand, Australia and Canada, red poppies are worn to commemorate soldiers who have died in times of war.
Lily
are used in burials as a symbol referring to "resurrection/life". It is also associated with stars (sun) and its petals blooming/shining.
Because of their varied and colorful appearance, flowers have long been a favorite subject of visual artists as well. Some of the most celebrated paintings from well-known painters are of flowers, such as
sunflowers series or Monet's water lilies. Flowers are also dried, freeze dried and pressed in order to create permanent, three-dimensional pieces of floral art
.
Flowers within art are also representative of the
Veronica Ruiz de Velasco, and Judy Chicago, and in fact in Asian and western classical art. Many cultures around the world have a marked tendency to associate flowers with femininity
.
The great variety of delicate and beautiful flowers has inspired the works of numerous poets, especially from the 18th–19th century
Ah! Sun-Flower
.
Their symbolism in dreams has also been discussed, with possible interpretations including "blossoming potential".[127]
The Roman goddess of flowers, gardens, and the season of Spring is
Flora. The Greek goddess of spring, flowers and nature is Chloris
.
In
Hindu mythology, flowers have a significant status. Vishnu, one of the three major gods in the Hindu system, is often depicted standing straight on a lotus flower.[128] Apart from the association with Vishnu, the Hindu tradition also considers the lotus to have spiritual significance.[129] For example, it figures in the Hindu stories of creation.[130]
History shows that flowers have been used by humans for thousands of years, to serve a variety of purposes. An early example of this is from about 4,500 years ago in Ancient Egypt, where flowers would be used to decorate women's hair. Flowers have also inspired art time and time again, such as in Monet's Water Lilies or William Wordsworth's poem about daffodils entitled: "I Wandered Lonely as a Cloud".[131]
In modern times, people have sought ways to cultivate, buy, wear, or otherwise be around flowers and blooming plants, partly because of their agreeable appearance and smell. Around the world, people use flowers to mark important events in their lives:
For wedding flowers for the bridal party, and as decorations for
wedding venues
As brightening decorations within the home
As a gift of remembrance for bon voyage parties, welcome-home parties, and "thinking of you" gifts
For funeral flowers and expressions of sympathy for the grieving
For worship. In
Hindu culture, adherents commonly bring flowers as a gift to temples[133]
A woman spreading flowers over a lingam in a temple in VaranasiFlowers collected for worship of Hindu deities in morning, in West Bengal.
Flowers like jasmine have been used as a replacement for traditional tea in China for centuries. Most recently many other herbs and flowers used traditionally across the world are gaining importance to preapare a range of floral tea.[citation needed]
People therefore grow flowers around their homes, dedicate parts of their living space to
developing economies through their availability as a fair trade product.[134]
Tampere Floral Festival
in July 2007.
Flowers provide less food than other major plant parts (
dandelion and elder are often made into wine. Bee pollen, pollen collected from bees, is considered a health food by some people. Honey consists of bee-processed flower nectar and is often named for the type of flower, e.g. orange blossom honey, clover honey and tupelo
The flower-giving tradition goes back to prehistoric times when flowers often had a medicinal and herbal attributes. Archaeologists found in several grave sites remnants of flower petals. Flowers were first used as sacrificial and burial objects.
. The practice of giving a flower flourished in the Middle Ages when couples showed affection through flowers.
The tradition of flower-giving exists in many forms. It is an important part of
Russian culture and folklore. It is common for students to give flowers to their teachers. To give yellow flowers in a romantic relationship means break-up in Russia. Nowadays, flowers are often given away in the form of a flower bouquet.[142][143][144]
^Sattler, R. (1988). "A dynamic multidimensional approach to floral development". In Leins, P.; Tucker, S.C. & Endress, P.K. (eds.). Aspects of Floral Development. Berlin: J. Cramer/Borntraeger. pp. 1–6.
JSTOR 3544245. Archived from the original on 2021-06-24. Retrieved 2021-06-20 – via JSTOR
. [T]he honey possum, Tarsipes rostratus (Turner 1983). This marsupial is highly specialized for feeding at flowers and known to visit several species of Banksia
from the original on 2021-06-25. Retrieved 2021-06-20 – via JSTOR. First, the effect may be direct, as, for example, the loss of one of the interacting partners in species-specific interactions may lead to the extinction of the other.
from the original on 2022-02-21. Retrieved 2021-07-01. Seeds on plants can be dispersed via a variety of primary dispersal mechanisms, including abiotic factors, like wind or ballistic projection, or biotic factors, like fruit-eating birds.
^
S2CID 86013249. Archived from the original on 2021-07-09. Retrieved 2021-07-01 – via JSTOR
. Wind and water are common abiotic seed dispersal mechanisms, but there are several biotic dispersal mechanisms, such as movement via animals by adhesion (epizoochory) or ingestion (endozoochory), and even movement resulting from human activities (anthropochory).
from the original on 2021-07-09. Retrieved 2021-07-01. Many studies show that germination is more successful after seeds pass through the digestive tract of frugivores