Floral symmetry describes whether, how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all because their parts are spirally arranged. Most flowers are actinomorphic, meaning they can be divided into 3 or more identical sectors which are related to each other by rotation about the centre of the flower; each sector might contain one tepal or one petal and one sepal and so on. It may or may not be possible to divide the flower into symmetrical halves by the same number of longitudinal planes passing through the axis: Oleander is an example of a flower without such mirror planes. Actinomorphic flowers are called radially symmetrical or regular flowers. Other examples of actinomorphic flowers are the buttercup. Zygomorphic flowers can be divided by only a single plane into two mirror-image halves, much like a yoke or a person's face. Examples are the flowers of most members of the Lamiales; some authors prefer bilateral symmetry.
A few plant species have flowers lacking any symmetry, therefore having a "handedness". Examples: Valeriana officinalis and Canna indica. Actinomorphic flowers are a basal angiosperm character; some familiar and actinomorphic so-called flowers, such as those of daisies and dandelions, most species of Protea, are clusters of tiny flowers arranged into a radially symmetric inflorescence of the form known as a head, capitulum, or pseudanthium. Peloria or a peloric flower is the aberration in which a plant that produces zygomorphic flowers produces actinomorphic flowers instead; this aberration can be developmental, or it can have a genetic basis: the CYCLOIDEA gene controls floral symmetry. Peloric Antirrhinum plants have been produced by knocking out this gene. Many modern cultivars of Sinningia speciosa have been bred to have peloric flowers as they are larger and showier than the zygomorphic flowers of this species. Charles Darwin explored peloria in Antirrhinum while researching the inheritance of floral characteristics for his The Variation of Animals and Plants under Domestication.
Research, using Digitalis purpurea, showed that his results were in line with Mendelian theory. If we consider only those flowers which consist in a single flower, rather than a flower head or inflorescence, we can group the flowers into a small number of 2D symmetry groups. Monocots are identifiable by their trimerous petals, thus monocots have rotational symmetry of order 3. If the flower has 3 lines of mirror symmetry the group it belongs to is the dihedral group D3. If not it belongs to the cyclic group C3. Eudicots with tetramerous or pentamerous petals may have rotational symmetry of order 4 or 5. Again, whether they have mirror planes decides whether they belong to dihedral or cyclic groups; the sepals of some monocot flowers develop to replicate the petals, superficially, certain monocots can appear to have rotational symmetry of order 6 and belong to either symmetry group D6 or C6. However, flower symmetry is perfect. Patterns in nature Phyllotaxis Symmetry in biology Whorl Craene, Louis P. Ronse De, Floral diagrams: an aid to understanding flower morphology and evolution, Cambridge: Cambridge University Press, ISBN 9780521493468 Darwin, Charles.
The variation of animals and plants under domestication. II. London: John Murray. Endress, P. K.. "Evolution of floral symmetry". Curr. Opin. Plant Biol. 4: 86–91. Doi:10.1016/S1369-526600140-0. PMID 11163173. Neal P. R.. "Floral symmetry and its role in plant-pollinator systems: terminology and hypotheses". Annu Rev Ecol Syst. 29: 345–373. Doi:10.1146/annurev.ecolsys.29.1.345. JSTOR 221712
Pyrus communis, known as the European pear or common pear, is a species of pear native to central and eastern Europe and southwest Asia. It is one of the most important fruits of temperate regions, being the species from which most orchard pear cultivars grown in Europe, North America, Australia have been developed. Two other species of pears, the Nashi pear and the hybrid Chinese white or ya pear are more grown in East Asia; the cultivated European pear is thought to be descended from two subspecies of wild pears, categorized as P. communis subsp. Pyraster and P. communis subsp. Caucasica, which are interfertile with domesticated pears. Archeological evidence shows these pears "were collected from the wild long before their introduction into cultivation", according to Zohary and Hopf. Although they point to finds of pears in sites in Neolithic and Bronze Age European sites, "reliable information on pear cultivation first appears in the works of the Greek and the Roman writers." Theophrastus, Cato the Elder, Pliny the Elder all present information about the cultivation and grafting of pears.
European pear trees are not nearly so. However, they do require some winter chilling to produce fruit. A number of Lepidoptera caterpillars feed on pear tree leaves. For best and most consistent quality, European pears are picked when the fruit matures, but before they are ripe. Fruit allowed to ripen on the tree drops before it can be picked, in any event will be hard to pick without bruising. Pears store well in their mature but unripe state if kept cold, can be ripened a process called bletting; some varieties, such as Beurre d'Anjou, ripen only with exposure to cold. Fermented pear juice is called perry. In Britain, the place name "Perry" can indicate the historical presence of pear trees. Few cultivars of European or Asian pears are grown worldwide. Only about 20-25 European and 10-20 Asian cultivars represent all the pears of commerce. All European cultivars were chance seedlings or selections originating in western Europe France; the Asian cultivars all originated in Japan and China.'Bartlett' is the most common pear cultivar in the world, representing about 75% of US pear production.
In the United States, 95% of reported pear production in 2004 came from four cultivars: 50% Williams' Bon Chrétien 34% Beurré d'Anjou 10% Beurré Bosc 1% Doyenné du Comice Those marked agm have gained the Royal Horticultural Society's Award of Garden Merit.'Abate Fetel"Ayers"Bambinella"Beth' agm Beurré Hardy/Gellerts Butterbirne'Blake's Pride"Blanquilla"Butirra Precoce Morettini"Carmen"Clara Frijs"Concorde' agm'Conference' agm'Corella"Coscia"Don Guindo"Doyenné du Comice"Dr. Jules Guyot"Forelle"Glou Morceau"Gorham"Harrow Delight"Harrow Sweet"Joséphine de Malines' agm'Kieffer"Laxton's Superb"Louise Bonne of Jersey' agm'Luscious"Merton Pride"Onward' agm'Orient"Packham's Triumph"Pineapple"Red Bartlett"Rocha"Rosemarie"Seckel"Starkrimson' called Red Clapp's, is a red-skinned 1939 Michigan bud mutation of Clapp's Favourite, its thick, smooth skin is a uniform and intense red, its creamy flesh is sweet and aromatic.'Summer Beauty"Sudduth"Taylor's Gold' Triomphe de Vienne'Williams Bonne Chrétienne' agm Pyrus communis images at bioimages.vanderbilt.edu
Campanula medium, common name Canterbury bells known as the bell flower, is an annual or biennial flowering plant of the genus Campanula, belonging to the family Campanulaceae. In floriography, it represents faith and constancy; the genus Latin name, meaning small bell, refers to the bell-shape of the flower, while the specific epithet means that this plant has intermediate characteristics in respect of other species of the same genus. In Persian, it is called گل استکانی meaning "Glass flower". Campanula medium reaches 60–80 centimetres in height; this biennial herbaceous plant forms rosettes of leaves in the first year and flowers in the second one. The stem is erect, reddish-brown and bristly hairy; the basal leaves are stalked and lanceolate to elliptical and 12–15 centimetres long with serrated leaf edge. The upper leaves are smaller and sessile embracing the stem; the flowers are arranged in a racemose inflorescence of long lasting blooms. These attractive bell-shaped flowers are short-stalked and hermaphroditic, with different shades of violet-blue or white.
The corolla has five fused petals with bent lobes. The flowering period extends from May to July in the northern hemisphere; the hermaphroditic flowers pollinated by insects. The seeds ripen from Aug to September and are dispersed by gravity alone. Campanula medium originates in southern Europe, it is naturalized in most of European countries and in North America and it is cultivated for its beautiful flowers. It grows on stony and bushy slopes, at an altitude of 0–1,500 metres above sea level. In gardens, they are best in massed planting among shrubs, it prefers warm zones. Seeds take 14–21 days to germinate; the plant thrives in shaded to sunny locations in well-drained soil. Canterbury bells grows nicely in flower beds and containers. Keep well watered; this flower works well cut in floral arrangements. Beekeepers sometimes use the Canterbury Bell for making potently sweet honey. Campanula medium'Alba' Campanula medium'Bells of Holland' Campanula medium'Caerulea' Campanula medium'Calycanthema' Campanula medium'Champion Blue Campanula medium'Champion lavender' Campanula medium'Champion Pink' Campanula medium'Chelsea Pink' Campanula medium'Muse Rose' Campanula medium'Rosea' Campanula medium'Russian Pink' Pink, A..
Gardening for the Million. Project Gutenberg Literary Archive Foundation. Pignatti S. - Flora d'Italia – Edagricole – 1982, Vol. II, pag. 682 Data related to Campanula medium at Wikispecies Media related to Campanula medium at Wikimedia Commons Biolib Plants Campanula medium
Nectar is a sugar-rich liquid produced by plants in glands called nectaries, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide antiherbivore protection. Common nectar-consuming pollinators include mosquitoes, wasps, bees and moths, hummingbirds and bats. Nectar plays an important role in the foraging economics and overall evolution of nectar-eating species. Nectar is the sugar source for honey, it is useful in agriculture and horticulture because the adult stages of some predatory insects feed on nectar. For example, the social wasp species Apoica flavissima relies on nectar as a primary food source. In turn, these wasps hunt agricultural pest insects as food for their young. For example, thread-waisted wasps are known for hunting caterpillars. Caterpillars however, do become butterflies and moths, which are important pollinators. Nectar secretion increases as the flower is visited by pollinators.
After pollination, the nectar is reabsorbed into the plant. Nectar is derived from the fabled drink of Greek gods; the word is derived as a compound of nek, meaning death, tar, meaning the ability to overcome. The common use of nectar refers to the "sweet liquid in flowers", first recorded in AD 1600. A nectary is floral tissue found in different locations in the flower; the different types of floral nectaries include sepal nectaries, petal nectaries, staminal nectaries found on the stamen, gynoecial nectaries found on the ovary tissue. The nectaries may vary in color and symmetry. Nectaries can be categorized as structural or non-structural. Structural nectaries refer to specific areas of tissue that exude nectar, such as the types of floral nectaries listed. Non-structural nectaries secrete nectar infrequently from non-differentiated tissues; the different types of floral nectaries coevolved depending on the pollinator that feeds on the plant's nectar. Nectar is secreted from epidermal cells of the nectaries by means of modified stomata.
The nectar comes from phloem with additional sugars that are secreted from the cells through vesicles packaged by the endoplasmic reticulum. Flowers that have longer nectaries sometimes have a vascular strand in the nectary to assist in transport over a longer distance.. Floral nectaries are used by plants to attract pollinators such as insects and other vertebrates; the pollinators feed on the nectar and depending on the location of the nectary the pollinator assists in fertilization and outcrossing of the plant as they brush against the reproductive organs, the stamen and pistil, of the plant and pick up or deposit pollen. Nectar from floral nectaries is sometimes used as a reward to insects, such as ants, that protect the plant from predators. Many floral families have evolved a nectar spur; these spurs are projections of various lengths formed from different tissues, such as the petals or sepals. They allow for pollinators to land on the elongated tissue and more reach the nectaries and obtain the nectar reward.
Different characteristics of the spur, such as its length or position in the flower, may determine the type of pollinator that visits the flower. Defense from herbivory is one of the roles of extrafloral nectaries. Floral nectaries can be involved in defense. In addition to the sugars found in nectar, certain proteins may be found in nectar secreted by floral nectaries. In tobacco plants, these proteins have antimicrobial and antifungal properties and can be secreted to defend the gynoecium from certain pathogens. Floral nectaries have evolved and diverged into the different types of nectaries due to the various pollinators that visit the flowers. In Melastomataceae, different types of floral nectaries have been lost many times. Flowers that ancestrally produced nectar and had nectaries may have lost their ability to produce nectar due to a lack of nectar consumption by pollinators, such as certain species of bees. Instead they focused on energy allocation to pollen production. Species of angiosperms that have nectaries use the nectar to attract pollinators that consume the nectar, such as birds and butterflies.
In Bromeliaceae, septal nectaries are common in species that are bird pollinated. In species that are wind pollinated, nectaries are absent because there is no pollinator to provide a reward for. In flowers that are pollinated by long-tongued organism such as certain flies, moths and birds, nectaries in the ovaries are common because they are able to reach the nectar reward when pollinating. Sepal and petal nectaries are more common in species that are pollinated by short-tongued insects that cannot reach so far into the flower. Extrafloral nectaries are nectar-secreting plant glands that develop outside of flowers and are not involved in pollination, they are diverse in form, location and mechanism. They have been described in all above-ground plant parts—including leaves, stipules, cotyledons and stems, among others, they range from single-celled trichomes to complex cup-like structures that may or may not be vascularized. In contrast to floral nectaries, nectar produced outside the flower have a defensive function.
The nectar attracts predatory insects whic
An inflorescence is a group or cluster of flowers arranged on a stem, composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants; the modifications can involve the length and the nature of the internodes and the phyllotaxis, as well as variations in the proportions, swellings, adnations and reduction of main and secondary axes. Inflorescence can be defined as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern; the stem holding the whole inflorescence is called a peduncle and the major axis holding the flowers or more branches within the inflorescence is called the rachis. The stalk of each single flower is called a pedicel. A flower, not part of an inflorescence is called a solitary flower and its stalk is referred to as a peduncle. Any flower in an inflorescence may be referred to as a floret when the individual flowers are small and borne in a tight cluster, such as in a pseudanthium.
The fruiting stage of an inflorescence is known as an infructescence. Inflorescences may be complex; the rachis may be one of several types, including single, umbel, spike or raceme. Inflorescences are described by many different characteristics including how the flowers are arranged on the peduncle, the blooming order of the flowers and how different clusters of flowers are grouped within it; these terms are general representations. Inflorescences have modified shoots foliage different from the vegetative part of the plant. Considering the broadest meaning of the term, any leaf associated with an inflorescence is called a bract. A bract is located at the node where the main stem of the inflorescence forms, joined to the main stem of the plant, but other bracts can exist within the inflorescence itself, they serve a variety of functions which include protecting young flowers. According to the presence or absence of bracts and their characteristics we can distinguish: Ebracteate inflorescences: No bracts in the inflorescence.
Bracteate inflorescences: The bracts in the inflorescence are specialised, sometimes reduced to small scales, divided or dissected. Leafy inflorescences: Though reduced in size, the bracts are unspecialised and look like the typical leaves of the plant, so that the term flowering stem is applied instead of inflorescence; this use is not technically correct, as, despite their'normal' appearance, these leaves are considered, in fact, bracts, so that'leafy inflorescence' is preferable. Leafy-bracted inflorescences: Intermediate between bracteate and leafy inflorescence. If many bracts are present and they are connected to the stem, like in the family Asteraceae, the bracts might collectively be called an involucre. If the inflorescence has a second unit of bracts further up the stem, they might be called an involucel. Plant organs can grow according to two different schemes, namely monopodial or racemose and sympodial or cymose. In inflorescences these two different growth patterns are called indeterminate and determinate and indicate whether a terminal flower is formed and where flowering starts within the inflorescence.
Indeterminate inflorescence: Monopodial growth. The terminal bud keeps forming lateral flowers. A terminal flower is never formed. Determinate inflorescence: Sympodial growth; the terminal bud forms a terminal flower and dies out. Other flowers grow from lateral buds. Indeterminate and determinate inflorescences are sometimes referred to as open and closed inflorescences respectively; the indeterminate patterning of flowers is derived from determinate flowers. It is suggested that indeterminate flowers have a common mechanism that prevents terminal flower growth. Based on phylogenetic analyses, this mechanism arose independently multiple times in different species. In an indeterminate inflorescence there is no true terminal flower and the stem has a rudimentary end. In many cases the last true flower formed by the terminal bud straightens up, appearing to be a terminal flower. A vestige of the terminal bud may be noticed higher on the stem. In determinate inflorescences the terminal flower is the first to mature, while the others tend to mature starting from the bottom of the stem.
This pattern is called acropetal maturation. When flowers start to mature from the top of the stem, maturation is basipetal, while when the central mature first, divergent; as with leaves, flowers can be arranged on the stem according to many different patterns. See'Phyllotaxis' for in-depth descriptions Similarly arrangement of leaf in bud is called Ptyxis. Metatopy is the placement of organs out of their expected position: metatopy occurs in inflorescences when unequal growth rates alter different areas of the axis and the organs attached to the axis; when a single or a cluster of flower is located at the axil of a bract, the location of the bract in relation to the stem holding the flower is indicated by the use of different terms and may be a useful diagnostic indicator. Typical placement of bracts include: Some plants have bracts that subtend the inflorescence, where the flowers are on branched stalks.
Petals are modified leaves that surround the reproductive parts of flowers. They are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are accompanied by another set of special leaves called sepals, that collectively form the calyx and lie just beneath the corolla; the calyx and the corolla together make up the perianth. When the petals and sepals of a flower are difficult to distinguish, they are collectively called tepals. Examples of plants in which the term tepal is appropriate include genera such as Tulipa. Conversely, genera such as Rosa and Phaseolus have well-distinguished petals; when the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly coloured tepals. Since they include Liliales, an alternative name is lilioid monocots. Although petals are the most conspicuous parts of animal-pollinated flowers, wind-pollinated species, such as the grasses, either have small petals or lack them entirely.
The role of the corolla in plant evolution has been studied extensively since Charles Darwin postulated a theory of the origin of elongated corollae and corolla tubes. A corolla of separate tepals is apopetalous. If the petals are free from one another in the corolla, the plant is choripetalous. In the case of fused tepals, the term is syntepalous; the corolla in some plants forms a tube. Petals can differ in different species; the number of petals in a flower may hold clues to a plant's classification. For example, flowers on eudicots most have four or five petals while flowers on monocots have three or six petals, although there are many exceptions to this rule; the petal whorl or corolla may be bilaterally symmetrical. If all of the petals are identical in size and shape, the flower is said to be regular or actinomorphic. Many flowers are termed irregular or zygomorphic. In irregular flowers, other floral parts may be modified from the regular form, but the petals show the greatest deviation from radial symmetry.
Examples of zygomorphic flowers may be seen in members of the pea family. In many plants of the aster family such as the sunflower, Helianthus annuus, the circumference of the flower head is composed of ray florets; each ray floret is anatomically an individual flower with a single large petal. Florets in the centre of the disc have no or reduced petals. In some plants such as Narcissus the lower part of the petals or tepals are fused to form a floral cup above the ovary, from which the petals proper extend. Petal consists of two parts: the upper, broad part, similar to leaf blade called the blade and the lower part, similar to leaf petiole, called the claw, separated from each other at the limb. Claws are developed in petals of some flowers such as Erysimum cheiri; the inception and further development of petals shows a great variety of patterns. Petals of different species of plants vary in colour or colour pattern, both in visible light and in ultraviolet; such patterns function as guides to pollinators, are variously known as nectar guides, pollen guides, floral guides.
The genetics behind the formation of petals, in accordance with the ABC model of flower development, are that sepals, petals and carpels are modified versions of each other. It appears that the mechanisms to form petals evolved few times, rather than evolving from stamens. Pollination is an important step in the sexual reproduction of higher plants. Pollen is produced by the male organs of hermaphroditic flowers. Pollen does not move on its own and thus requires wind or animal pollinators to disperse the pollen to the stigma of the same or nearby flowers. However, pollinators are rather selective in determining the flowers; this develops competition between flowers and as a result flowers must provide incentives to appeal to pollinators. Petals play a major role in competing to attract pollinators. Henceforth pollination dispersal could occur and the survival of many species of flowers could prolong. Petals have various purposes depending on the type of plant. In general, petals operate to protect some parts of the flower and attract/repel specific pollinators.
This is where the positioning of the flower petals are located on the flower is the corolla e.g. the buttercup having shiny yellow flower petals which contain guidelines amongst the petals in aiding the pollinator towards the nectar. Pollinators have the ability to determine specific flowers. Using incentives flowers draw pollinators and set up a mutual relation between each other in which case the pollinators will remember to always guard and pollinate these flowers; the petals could produce different scents to allure desirable pollinators or repel undesirable pollinators. Some flowers will mimic the scents produced by materials such as decaying meat, to attract pollinators to them. Various colour traits are used by different petals that could attract pollinators that have poor smelling abilities, or that only come out at certain parts of the day; some flowers are able to change the colour