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Flower function The function of a flower is to mediate the union of male and female gametes in order to produce seeds. The process begins with pollination, is followed by fertilization, and continues with the formation and dispersal of the seed. Flower anatomy
Floral formula A floral formula is a way to represent the structure of a flower using specific letters, numbers, and symbols. Typically, a general formula will be used to represent the flower structure of a plant family rather than a particular species. The following representations are used: Ca = calyx (sepal whorl; e.g. Ca5 = 5 sepals) Co = corolla (petal whorl; e.g., Co3(x) = petals some multiple of three ) Z = add if zygomorphic (e.g., CoZ6 = zygomorphic with 6 petals) A = androecium (whorl of stamens; e.g., A∞ = many stamens) G = gynoecium (carpel or carpels; e.g., G1 = monocarpous) x - to represent a "variable number" ∞ - to represent "many" A floral formula would appear something like this: Ca5Co5A10 - ∞G1 Several other symbols are used that will have to await drawings to illustrate here (see *). Pollination
Attraction methods
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. Many flower rely on simple proximity between flower parts to ensure pollination. Others, such as the Sarracenia or lady-slipper orchids, have elaborate designs to ensure pollination while preventing self-pollination. The flowers of other species are pollinated by the wind (for example, grasses); they have no need to attract pollinators and therefore tend not to be "showy". Wind-pollinated flowers are referred to as anemophilous. 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. Honeybees and bumblebees actively gather anemophilous corn (maize) pollen, though it is of little value to them. 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. This close relationship is often given as an example of coevolution, as the flower and pollinator are thought to have developed together over a long period of time to match each other's needs. This close relationship compounds the negative effects of extinction. The extinction of either member in such a relationship would mean almost certain extinction of the other member as well. 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. Conversely, many species of plants have ways of preventing self-fertilization. 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. The latter flower types, which have chemical barriers to their own pollen, are referred to as self-sterile or self-incompatible (see also: Plant sexuality). 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; spores. In the sea, plants -- and some animals -- can simply scatter out little living copies of themselves to float away and grow elsewhere. This is how early plants, such as the modern fern, are thought to have reproduced. But plants soon began protecting these copies to deal with drying out and other abuse which is even more likely on land than in the sea. The protection became the seed...but not, yet, flowers. Early seed-bearing plants include the ginkgo, conifers (like pines), and fir trees. 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; the evidence has them springing in advanced form into the fossil record. 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. 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 fig wasps do today, could have eventually resulted in both the plant(s) and their partners developing a high degree of specialization. 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 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; one of the earliest examples of petrification. 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". 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*. 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. Flower vegetables include broccoli, cauliflower and artichoke. The most expensive spice, saffron, consists of dried stigmas of a crocus. Other flower spices are cloves and capers. 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. Dandelion flowers 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 honey. Hundreds of fresh flowers are edible but few are widely marketed as food. They are often used to add color and flavor to salads. Squash flowers are dipped in breadcrumbs and fried. Edible flowers include nasturtium, chrysanthemum, carnation, cattail, honeysuckle, chicory, cornflower and sunflower. Certain edible flowers are sometimes candied such as pansy, daisy and rose. Horticulture and floristry Under Construction Main and related articles at: Floristry, Flower garden, Gardening, Horticulture, and List of flowers Flowers in the arts
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: People 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
Gallery Image:DirkvdM red hairy flower 2.jpg| Image:DirkvdM red flat epiphyte.jpg| Image:DirkvdM red-white-stripe flower.jpg| Image:DirkvdM hairy fly.jpg| Image:DirkvdM yellow flower dew.jpg| Image:DirkvdM fence-flower.jpg| Image:DirkvdM bananaflower.jpg| Image:DirkvdM psychoberryflowers 2.jpg| Image:DirkvdM psychoberryflowers 5.jpg| Image:DirkvdM sensual flower.jpg| Image:DirkvdM sara longwing-2.jpg| Image:DirkvdM spiky flower red.jpg| Image:DirkvdM spiky flower white.jpg| Image:DirkvdM coloradobeetleflower.jpg| Image:DirkvdM ladybird.jpg| Image:DirkvdM psychoberryflowers 6.jpg| See also | |||||||||||||||||||
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