The reproductive organ of a flowering plant (angiosperm) derived from a leafy shoot of limited growth in which the leaves are modified for specific roles. It typically consists of four distinct whorls of parts attached to a receptacle: the sepals (calyx), the petals (corolla), the stamens (andrecium), and the carpels or ovary (gynecium). The parts of any whorl may be fused or otherwise highly modified or absent. Structurally, flowers can be divided into two types: actinomorphic or radially symmetrical, and zygomorphic or bilaterally symmetrical. Both the colour and structure of the flower are closely linked to the method of pollination: brightly-coloured petals, along with any scent or nectar produced by the flower are used to attract pollinators. The colour may be quite specific, so that red is typically a bird-colour, blue and yellow are bee-colours, and dull-purplish flowers are often wasp-pollinated. Flowers which are one colour in the visible spectrum may be another colour in the ultraviolet, visible to many insects. The structure, especially in zygomorphic flowers, may also be geared to particular visitors: flat, open blossoms are visited by a wide range of pollinators, including flies and beetles; more complex blooms may have nectar concealed in long, gullet-like corolla tubes or behind closed lips accessible only to long-tongued bees, moths, or humming-birds. In wind-pollinated flowers, attractive petals are superfluous, and are usually much-reduced or absent. Double or multiple-petalled flowers such as garden roses are rare in nature, being mostly the product of horticultural breeding.
A flower, (<Old French flo(u)r<Latin florem<flos), also known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Magnoliophyta, also called angiosperms). The flower structure contains the plant's reproductive organs, and its function is to produce seeds through reproduction.
Flower function
The function of a flower is to mediate the union of male and female gametes in order to produce seeds.
Flower anatomy
Flowering plants heterosporangiate (producing two types of reproductive spores).
A flower is regarded as a modified stem (Eames, 1961) with shortened internodes and bearing, at its nodes, structures that may be highly modified leaves. A pistil may consist of a number of carpels merged together, in which case there is only one pistil to each flower, or of a single individual carpel (the flower is then called apocarpous). These modifications have significance in the evolution of flowering plants and are used extensively by botanists to establish relationships among plant species.
In the majority of species individual flowers have both pistils and stamens as described above. However, in some species of plants the flowers are imperfect or unisexual: having only either male (stamens) or female (pistil) parts. However, where unisexual male and female flowers appear on the same plant, the species is considered monoecious.
Additional discussions on floral modifications from the basic plan are presented in the articles on each of the basic parts of the flower. In those species that have more than one flower on an axis—so-called composite flowers— the collection of flowers is termed an inflorescence; this term can also refer to the specific arrangements of flowers on a stem. In botanical terminology, a single daisy or sunflower for example, is not a flower but a flower head— an inflorescence composed of numerous tiny flowers (sometimes called florets). Each of these flowers may be anatomically as described above.
Floral formula
A floral formula is a way to represent the structure of a flower using specific letters, numbers, and symbols. e.g., G1 = monocarpous)
x - to represent a "variable number"
∞ - to represent "many"
A floral formula would appear something like this:
CaASeveral other symbols are used that will have to await drawings to illustrate here (see ).
Pollination
Also see the main article on pollination.
The primary purpose of a flower is to join the pollen of one plant with the ovules of another (or in some cases its own ovules) in order to
form seed which is genetically unique, allowing for adaptation to occur. Many flowers are dependent upon the wind to move pollen between flowers of the same species.
Attraction methods
Many flowers in nature have evolved to attract animals to pollinate the flower, the movements of the pollinating agent contributing to the opportunity for genetic recombination within a dispersed plant population. Flowers that are insect-pollinated are called entomophilous (literally "insect-loving"). Flowers commonly have glands called nectaries on their various parts that attract these animals. Birds and bees are common pollinators: both having color vision, thus opting for "colorful" flowers. Some flowers have patterns, called nectar guides, that show pollinators where to look for nectar; Flowers also attract pollinators by scent. Flowers pollinated by night visitors such as bats or moths are especially likely to concentrate on scent - which can attract pollinators in the dark - rather than color: most such flowers are white.
Still other flowers use mimicry to attract pollinators. Some species of orchids, for example, produce flowers resembling female bees in color, shape, and scent.
Pollination mechanism
The pollination mechanism employed by a plant depends on what method of pollination is desired.
Entomophilous flowers (those which employ insects to transfer pollen) have an arrangement of the stamens that ensures that pollen grains are transferred to the bodies of the pollinator when it lands in search of its attractant (such as nectar, pollen, or a mate). In pursuing this attractant from many flowers of the same species, the pollinator transfers pollen to the stigmas - arranged with equally pointed precision - of all of the flowers it visits.
The flowers of other species are pollinated by the wind (for example, grasses); Whereas the pollen of entomophilous flowers tends to be large-grained, sticky, and rich in protein (another "reward" for pollinators), anemophilous flower pollen is usually small-grained, very light, and of little nutritional value to insects, though it may still be gathered in times of dearth.
Flower-pollinator relationships
Many flowers have close relationships with one or a few specific pollinating organisms. Many flowers, for example, attract only one specific species of insect, and therefore rely on that insect for successful reproduction.
Fertilization
Some flowers with both stamens and a pistil are capable of self-fertilization, which does increase the chance of producing seeds but limits genetic variation. The extreme case of
self-fertilization occurs in flowers that always self-fertilize, such as many dandelions. Unisexual male and female flowers on the same plant may not appear or mature at the same time, or
pollen from the same plant may be incapable of fertilizing its ovules.
Seed production
Seed dispersal
See also main article on dispersal
Flower evolution
While land plants have existed for about 425 million years, the first ones reproduced by a simple adaptation of their aquatic counterparts; But the first fossil proof of actual flowers appears only 130 million years ago.
Unfortunately, there is no fossil evidence of exactly how flowers evolved; This was recognized almost immediately during the development of evolution theory, the strange appearance of flowers in the fossil record being called by Charles Darwin the Abominable Mystery.
The general assumption is that the function of flowers, from the start, was to involve other animals in the reproduction process. 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.
Likewise, most fruit used in plant reproduction comes from the enlargement of parts of the flower.
While many such symbiotic relationships remain too fragile to survive competition with mainland animals and spread, flowers proved to be an unusually effective means of production, spreading (whatever their actual origin) to become the dominant form of land plant life.
While there is only hard proof of such flowers existing about 130 million years ago, there is some circumstantial evidence that they did exist up to 250 million years ago. A chemical used by plants to defend their flowers, oleanane, has been detected in fossil plants that old, including gigantopterids, 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;
The similarity in leaf and stem structure can be very important, because flowers are genetically just an adaptation of normal leaf and stem components on plants, a combination of genes normally responsible for forming new shoots. The most primitive flowers are thought to have had a variable number of flower parts, often separate from (but in contact with) each other. The flowers would have tended to grow in a spiral pattern, to be bisexual (in plants, this means both male and female parts on the same flower), and to be dominated by the 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". 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.
Uses by humans
Edible flowers
Flowers provide less food than other major plants parts (seeds, fruits, roots, stems and leaves) but they provide several important foods and spices. Hops flowers are used to flavor beer. Marigold flowers are fed to chickens to give their skin a golden yellow color, which consumers find more desirable.
Hundreds of fresh flowers are edible but few are widely marketed as food. Edible flowers include nasturtium, chrysanthemum, carnation, cattail, honeysuckle, chicory, cornflower and sunflower.
Horticulture and floristry
Under Construction
Main and related articles at: Floristry, Flower garden, Gardening, Horticulture, and List of flowers
Flowers in the arts
The great variety of delicate and beautiful flowers has inspired the works of many poets, especially from the Romantic era.
Because of their varied and colorful appearance, flowers have long been a favorite subject of visual artists as well.
The Roman goddess of flowers, gardens, and the season of Spring is Flora.
Flowers in everyday life
In modern times, people have sought ways to cultivate, buy, wear, or just be around flowers and blooming plants, partly because of their agreeable smell. Around the world, people use flowers for a wide range of events and functions that, cumulatively, encompass one's lifetime:
For new births or Christenings As a corsage or boutonniere to be worn at social functions or for holidays For wedding flowers for the bridal party, and decorations for the hall 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 grievingPeople therefore grow flowers around their homes, dedicate entire parts of their living space to flower gardens, pick wildflowers, or buy flowers from florists who depend on an entire network of commercial growers and shippers to support their trade.
Flowers as symbols
Many flowers have important symbolic meanings in Western culture.
Flowers within art are also representative of the female genitalia, as seen in the works of artists such as Georgia O'Keefe, Imogen Cunningham, Veronica Ruiz de Velasco, and Judy Chicago, and in fact in Asian and western classical art.
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