A flower, sometimes known as a bloom or blossom Blossom is a term given to the flowers of stone fruit trees and of some other plants with a similar appearance that flower profusely for a period of time in spring. Blossoms are either pink or white depending on the species or variety. Nectarine blossoms, peach blossoms, most cherry blossoms, and some almond blossoms are usually pink. Plum, is the reproductive Reproduction is the biological process by which new "offspring" individual organisms are produced from their "parents". Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: sexual and structure found in flowering plants The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Together with gymnosperms, they are the only extant groups of seed-producing plants, but they can be distinguished from the gymnosperms by a series of synapomorphies (derived characteristics). These characteristics include flowers, (plants of the division Magnoliophyta The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Together with gymnosperms, they are the only extant groups of seed-producing plants, but they can be distinguished from the gymnosperms by a series of synapomorphies (derived characteristics). These characteristics include flowers,, also called angiosperms). The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds. The process begins with pollination, is followed by fertilization, leading to the formation and dispersal of the seeds. For the higher plants, seeds are the next generation, and serve as the primary means by which individuals of a species are dispersed across the landscape. The grouping of flowers on a plant is called the inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified. The modifications can involve the length and the nature of the internodes and the.
In addition to serving as the reproductive organs of flowering plants, flowers have long been admired and used by humans, mainly to beautify their environment but also as a source of food.
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Flower specialization and pollination
Further information: Pollination syndrome Callistemon citrinus flowersFlowering plants usually face selective pressure to optimise the transfer of their 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 between the stamens to the pistil of flowering plants or from the male cone to the female cone of coniferous plants. When pollen lands, and this is typically reflected in the morphology of the flowers and the behaviour of the plants. Pollen may be transferred between plants via a number of 'vectors'. Some plants make use of abiotic vectors — namely wind (anemophily Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Anemophilous plants may be either gymnosperms or angiosperms (flower-producing). However, flowering anemophilous species do not develop scented flowers, nor do they produce nectar. This distinguishes them from entomophilous and zoophilous species (whose) or, much less commonly, water (hydrophily Hydrophily is a fairly uncommon form of pollination whereby pollen is distributed by the flow of waters, particularly in rivers and streams). Others use biotic vectors including insects (entomophily Entomophily is a form of pollination whereby pollen is distributed by insects, particularly bees, Lepidoptera , flies and beetles. Entomophilous species frequently evolve mechanisms to make themselves more appealing to insects, e.g., brightly-colored or scented flowers, nectar, or appealing shapes and patterns. Pollen grains of entomophilous), birds (ornithophily Ornithophily is the pollination of flowering plants by birds. This coevolutionary association is derived from insect pollination and is particularly well developed in some parts of the world, especially in the tropics and on some island chains. The association involves several distinctive plant adaptations forming a "pollination syndrome"), bats (chiropterophily Pollination syndromes are suites of flower traits that have evolved in response to natural selection imposed by different pollen vectors, which can be abiotic or biotic, such as birds, bees, flies, and so forth. These traits include flower shape, size, colour, odour, reward type and amount, nectar composition, timing of flowering, etc. For example,) or other animals. Some plants make use of multiple vectors, but many are highly specialised.
Cleistogamous flowers Cleistogamy or automatic self-pollination describes the trait of certain plants to propagate by using non-opening, self-pollinating flowers. Especially in peanuts, peas, and beans, this behaviour is most widespread in the grass family, though the largest genus of cleistogamous plants is actually Viola are self pollinated, after which they may or may not open. Many Viola and some Salvia species are known to have these types of flowers.
The flowers of plants that make use of biotic pollen vectors commonly have glands called nectaries Nectar is a sugar-rich liquid produced by plants. It is produced either by the flowers, in which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists providing anti-herbivore protection. It is produced in glands called nectaries. Common nectar-consuming pollinators include bees, that act as an incentive for animals to visit the flower. Some flowers have patterns, called nectar guides Nectar guides are patterns seen in some flowers that guide pollinators to the nectar and pollen, that show pollinators where to look for nectar. Flowers also attract pollinators by scent and color. Still other flowers use mimicry to attract pollinators. Some species of orchids, for example, produce flowers resembling female bees in color, shape, and scent. Flowers are also specialized in shape and have an arrangement of the stamens The stamen is the male reproductive organ of a flower. Each stamen generally has a stalk called the filament (from Latin filum, meaning "thread"), and, on top of the filament, an anther (from Ancient Greek anthera, feminine of antheros "flowery," from anthos "flower"), and pollen sacs, called microsporangia. The 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.
Anemophilous flowers Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Anemophilous plants may be either gymnosperms or angiosperms (flower-producing). However, flowering anemophilous species do not develop scented flowers, nor do they produce nectar. This distinguishes them from entomophilous and zoophilous species (whose use the wind to move pollen from one flower to the next. Examples include grasses, birch trees, ragweed and maples. They have no need to attract pollinators and therefore tend not to be "showy" flowers. Male and female reproductive organs are generally found in separate flowers, the male flowers having a number of long filaments terminating in exposed stamens, and the female flowers having long, feather-like stigmas. Whereas the pollen of animal-pollinated flowers tends to be large-grained, sticky, and rich in protein Proteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded (another "reward" for pollinators), anemophilous flower pollen is usually small-grained, very light, and of little nutritional value to animals.
Morphology
Flowering plants are heterosporangiate, producing two types of reproductive spores In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoans. A chief difference between spores and seeds as dispersal units is that spores have very little stored. The 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 between the stamens to the pistil of flowering plants or from the male cone to the female cone of coniferous plants. When pollen lands (male spores) and ovules Ovule literally 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 integuments forming its outer layer, the nucellus , and the megaspore-derived female gametophyte (or megagametophyte) in its center. The megagametophyte (also called (female spores) are produced in different organs In biology and anatomy, an organ is a collection of tissues joined in structural unit to serve a common function, but the typical flower is a bisporangiate strobilus in that it contains both organs.
A flower is regarded as a modified stem A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes distance one node from another. The term shoots is often confused with stems; shoots generally refer to new fresh with shortened internodes and bearing, at its nodes A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes distance one node from another. The term shoots is often confused with stems; shoots generally refer to new fresh, structures that may be highly modified leaves In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. As an evolutionary trait, the flatness of leaves works to expose the chloroplasts to more light and to increase the absorption of carbon dioxide at the expense of water loss. In the Devonian period, when carbon.[1] In essence, a flower structure forms on a modified shoot or axis with an apical meristem A meristem is the tissue in all plants consisting of undifferentiated cells and found in zones of the plant where growth can take place that does not grow continuously (growth is determinate). Flowers may be attached to the plant in a few ways. If the flower has no stem but forms in the axil of a leaf, it is called sessile. When one flower is produced, the stem holding the flower is called a peduncle In botany, a peduncle is a stalk supporting an inflorescence, or after fecundation a fruit. If the peduncle ends with groups of flowers, each stem that holds a flower is called a pedicel A pedicel is a stem that attaches single flowers to the main stem of the inflorescence. It is the branches or stalks that hold each flower in an inflorescence that contains more than one flower. The flowering stem forms a terminal end which is called the torus or receptacle. The parts of a flower are arranged in whorls on the torus. The four main parts or whorls (starting from the base of the flower or lowest node and working upwards) are as follows:
Diagram showing the main parts of a mature flower An example of a "perfect flower", this Crateva religiosa flower has both stamens (outer ring) and a pistil (center).- Calyx A sepal is a part of the flower of angiosperms (flowering plants). Sepals in most flowers are green and lie under the more conspicuous petals. However, the term tepal is usually applied when the petals and sepals share the same color, or the petals are absent and the sepals are colorful. When the flower is in bud, the sepals enclose and protect: the outer whorl of sepals A sepal is a part of the flower of angiosperms (flowering plants). Sepals in most flowers are green and lie under the more conspicuous petals. However, the term tepal is usually applied when the petals and sepals share the same color, or the petals are absent and the sepals are colorful. When the flower is in bud, the sepals enclose and protect; typically these are green, but are petal-like in some species.
- Corolla A petal is one member or part of the corolla of a flower. The corolla is the name for all of the petals of a flower. The corolla (petals) and calyx (the name for all the sepals) make up the outer whorls of a flower; these form what is known as the perianth, which attracts pollinators with its bright color. The term "tepal" is usually: the whorl of petals A petal is one member or part of the corolla of a flower. The corolla is the name for all of the petals of a flower. The corolla (petals) and calyx (the name for all the sepals) make up the outer whorls of a flower; these form what is known as the perianth, which attracts pollinators with its bright color. The term "tepal" is usually, which are usually thin, soft and colored to attract animals that help the process of pollination Pollination is the process by which pollen is transferred in plants, thereby enabling fertilization and sexual reproduction. Pollen grains, which contain the male gametes to where the female gamete(s) are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself. The receptive part of the carpel is called a. The coloration may extend into the ultraviolet Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the colour violet, which is visible to the compound eyes Eyes are organs that detect light, and convert it to electro-chemical impulses in neurons. The simplest photoreceptors connect light to movement . In higher organisms complex neural pathways exist that connect the eye, via the optic nerve to the visual cortex and other areas of the brain. Complex optical systems with resolving power have come in of insects, but not to the eyes of birds.
- Androecium The stamen is the male reproductive organ of a flower. Each stamen generally has a stalk called the filament (from Latin filum, meaning "thread"), and, on top of the filament, an anther (from Ancient Greek anthera, feminine of antheros "flowery," from anthos "flower"), and pollen sacs, called microsporangia. The (from Greek andros oikia: man's house): one or two whorls of stamens The stamen is the male reproductive organ of a flower. Each stamen generally has a stalk called the filament (from Latin filum, meaning "thread"), and, on top of the filament, an anther (from Ancient Greek anthera, feminine of antheros "flowery," from anthos "flower"), and pollen sacs, called microsporangia. The, each a filament topped by an anther The stamen is the male reproductive organ of a flower. Each stamen generally has a stalk called the filament (from Latin filum, meaning "thread"), and, on top of the filament, an anther (from Ancient Greek anthera, feminine of antheros "flowery," from anthos "flower"), and pollen sacs, called microsporangia. The where 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 between the stamens to the pistil of flowering plants or from the male cone to the female cone of coniferous plants. When pollen lands is produced. Pollen contains the male gametes A gamete is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual that produces the larger type of gamete—called an ovum (or egg)—and a.
- Gynoecium The gynoecium is a term with several meanings in botanical usage. In reference to mosses; liverworts; and hornworts, gynoecium refers to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot. The more common use of gynoecium, however, is to refer to the ovule-producing part of a flower. The gynoecium in (from Greek gynaikos oikia: woman's house): one or more pistils The gynoecium is a term with several meanings in botanical usage. In reference to mosses; liverworts; and hornworts, gynoecium refers to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot. The more common use of gynoecium, however, is to refer to the ovule-producing part of a flower. The gynoecium in. The female reproductive organ is the carpel The gynoecium is a term with several meanings in botanical usage. In reference to mosses; liverworts; and hornworts, gynoecium refers to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot. The more common use of gynoecium, however, is to refer to the ovule-producing part of a flower. The gynoecium in: this contains an ovary with ovules (which contain female gametes). 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). The sticky tip of the pistil, the stigma, is the receptor of pollen. The supportive stalk, the style becomes the pathway for pollen tubes The pollen tube of most seed plants acts as a conduit to transport 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 (conifers and gnetophytes). In other gymnosperms (Ginkgo and cycads) the pollen tube is involved only in nutrient uptake from to grow from pollen grains adhering to the stigma, to the ovules, carrying the reproductive material.
Although the floral structure described above is considered the "typical" structural plan, plant species show a wide variety of modifications from this plan. These modifications have significance in the evolution of flowering plants and are used extensively by botanists to establish relationships among plant species. For example, the two subclasses of flowering plants may be distinguished by the number of floral organs in each whorl: dicotyledons The dicotyledons, also known as dicots, are a group of flowering plants whose seed typically has two embryonic leaves or cotyledons. There are around 199,350 species within this group. Flowering plants that are not dicotyledons are monocotyledons, typically having one embryonic leaf typically having 4 or 5 organs (or a multiple of 4 or 5) in each whorl and monocotyledons Monocotyledons, also known as monocots, are one of two major groups of flowering plants that are traditionally recognized, the other being dicotyledons, or dicots. Monocot seedlings typically have one cotyledon (seed-leaf), in contrast to the two cotyledons typical of dicots. Monocots have been recognized at various taxonomic ranks, and under having three or some multiple of three. The number of carpels in a compound pistil may be only two, or otherwise not related to the above generalization for monocots and dicots.
In the majority of species individual flowers have both pistils The gynoecium is a term with several meanings in botanical usage. In reference to mosses; liverworts; and hornworts, gynoecium refers to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot. The more common use of gynoecium, however, is to refer to the ovule-producing part of a flower. The gynoecium in and stamens as described above. These flowers are described by botanists as being perfect, bisexual, or hermaphrodite In biology, a hermaphrodite is a plant or animal that has reproductive organs normally associated with both male and female sexes . Many taxonomic groups of animals , do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both partners can act as the "female" or. However, in some species of plants the flowers are imperfect or unisexual: having only either male (stamens) or female (pistil) parts. In the latter case, if an individual plant is either female or male the species is regarded as dioecious. 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 An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified. The modifications can involve the length and the nature of the internodes and the; this term can also refer to the specific arrangements of flowers on a stem. In this regard, care must be exercised in considering what a ‘‘flower’’ is. In botanical terminology, a single daisy or sunflower Sunflowers are annual plants native to the Americas, that possess a large inflorescence (flowering head) for example, is not a flower but a flower head The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization—an inflorescence composed of numerous tiny flowers (sometimes called florets). Each of these flowers may be anatomically as described above. Many flowers have a symmetry, if the perianth is bisected through the central axis from any point, symmetrical halves are produced—the flower is called regular or actinomorphic, e.g. rose or trillium. When flowers are bisected and produce only one line that produces symmetrical halves the flower is said to be irregular or zygomorphic. e.g. snapdragon or most orchids.
Christmas Lillium (Lilium longiflorum). 1. Stigma, 2. Style, 3. Stamens, 4. Filament, 5. PetalFloral 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 additional symbols are sometimes used (see Key to Floral Formulas).
The four main parts of a flower are generally defined by their positions on the receptacle and not by their function. Many flowers lack some parts or parts may be modified into other functions and/or look like what is typically another part. In some families, like Ranunculaceae, the petals are greatly reduced and in many species the sepals are colorful and petal-like. Other flowers have modified stamens that are petal-like, the double flowers of Peonies and Roses are mostly petaloid stamens.[2] Flowers show great variation and plant scientists describe this variation in a systematic way to identify and distinguish species.
Specific terminology is used to descried flowers and their parts. Many flower parts are fused together; fused parts originating from the same whorl are connate, while fused parts originating from different whorls are adnate, parts that are not fused are free. When petals are fused into a tube or ring that falls away as a single unit, they are sympetalous (also called gamopetalous.) Petals that are connate may have distinctive regions: the cylindrical base is the tube, the expanding region is the throat and the flaring outer region is the limb. A sympetalous flower, with bilateral symmetry with an upper and lower lip, is bilabiate. Flowers with connate petals or sepals may have various shaped corolla or calyx including: campanulate, funnelform, tubular, urceolate, salverform or rotate.
Development
Flowering transition
The transition to flowering is one of the major phase changes that a plant makes during its life cycle. The transition must take place at a time that is favorable for fertilization and the formation of seeds, hence ensuring maximal reproductive success. To meet these needs a plant is able to interpret important endogenous and environmental cues such as changes in levels of plant hormones and seasonable temperature and photoperiod changes.[3] Many perennial and most biennial plants require vernalization to flower. The molecular interpretation of these signals is through the transmission of a complex signal known as florigen, which involves a variety of genes, including CONSTANS, FLOWERING LOCUS C and FLOWERING LOCUS T. Florigen is produced in the leaves in reproductively favorable conditions and acts in buds and growing tips to induce a number of different physiological and morphological changes.[4] The first step is the transformation of the vegetative stem primordia into floral primordia. This occurs as biochemical changes take place to change cellular differentiation of leaf, bud and stem tissues into tissue that will grow into the reproductive organs. Growth of the central part of the stem tip stops or flattens out and the sides develop protuberances in a whorled or spiral fashion around the outside of the stem end. These protuberances develop into the sepals, petals, stamens, and carpels. Once this process begins, in most plants, it cannot be reversed and the stems develop flowers, even if the initial start of the flower formation event was dependent of some environmental cue.[5] Once the process begins, even if that cue is removed the stem will continue to develop a flower.
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