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what is mistletoe

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what is mistletoe

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  1. http://en.wikipedia.org/wiki/MistletoeMistletoe in the genus ViscumThe name was originally applied to Viscum album(European Mistletoe, Santalaceae), the only species native in Great Britainand much of Europe. European mistletoe, Viscum albumis readily recognized by its smooth-edged ovalevergreen leaves borne in pairs along the woody stem, and waxy white berries in dense clusters of 2 to 6. In America the genus Viscumdoes not grow wild but the Eastern Mistletoe (in the genus Phoradendron) is similar, but has shorter, broader leaves and longer clusters of 10 or more berries.Viscum albumis a poisonous plant that causes acute gastrointestinal problems including stomach pain, and diarrheaalong with low pulse.[1]However, both European Mistletoe and the North American species, Phoradendronserotinum, are commercially harvested for Christmas decorations.[2][edit] Other mistletoe groupsLater the name was further extended to other related species and even families, including Phoradendronserotinum(the Eastern Mistletoe of eastern North America, also Santalaceae).The largest family of Mistletoes, Loranthaceae, has 73 genera and over 900 species.[3]Subtropicaland tropicalclimateshave markedly more Mistletoe species; Australiahas 85, of which 71 are in Loranthaceae, and 14 in Santalaceae.[4]Parasitismhas evolved only nine times in the plant kingdom;[5]of those, the parasitic mistletoe habit has evolved independently five times: Misodendraceae, Loranthaceae, and Santalaceae, including the former separate families Eremolepidaceaeand Viscaceae. Although Viscaceae and Eremolepidaceae were placed in a broadly-defined Santalaceae by Angiosperm Phylogeny GroupII, DNA data indicates that they evolved independently.[citation needed][edit] Life cycleMistletoe in winterMistletoe plants grow on a wide range of host trees, and commonly reduce their growth but can kill them with heavy infestation. Viscum albumcan parasitise more than 200 tree and shrub species. All mistletoes are hemi-parasites, bearing evergreenleavesthat do some photosynthesis, and using the host mainly for water and mineral nutrients. However, the mistletoe first sprouts from bird feces[citation needed]on the trunk of the tree and in its early stages of life takes it nutrients from this source.[citation needed]Species more or less completely parasitic include the leafless quintral, Tristerixaphyllus, which lives deep inside the sugar-transporting tissue of a spiny cactus, appearing only to show its tubular red flowers,[6]and the genus Arceuthobium(dwarf mistletoe; Santalaceae) which has reduced photosynthesis; as an adult, it manufactures only a small proportion of the sugarsit needs from its own photosythesis but as a seedlingit actively photosynthesizes until a connection to the host is established.Some species of the largest family, Loranthaceae, have small, insect-pollinatedflowers(as with Santalaceae), but others have spectacularly showy, large, bird-pollinatedflowers.Most mistletoe seeds are spread by birds, such as the Mistle Thrushin Europe, the Phainopeplain southwestern North America, and Dicaeumof Asiaand Australia. However, distinguishing between these species and ones of other ecological biomes is not difficult. They derive sustenance and agility through eating the fruits and nuts (drupes). The seeds are excreted in their droppings and stick to twigs, or more commonly the bird grips the fruit in its bill, squeezes the sticky coated seed out to the side, and then wipes its bill clean on a suitable branch.[citation needed]The seeds are coated with a sticky material called viscin (containing both cellulosicstrands and mucopolysaccharides), which hardens and attaches the seed firmly to its future host.[edit] Ecological importanceMistletoe was often considered a pest that kills trees and devalues natural habitats, but was recently recognized as an ecological keystone species, an organism that has a disproportionately pervasive influence over its community.[7]A broad array of animals depend on mistletoe for food, consuming the leaves and young shoots, transferring pollenbetween plants, and dispersing the sticky seeds. The dense evergreen witches' broomsformed by the dwarf mistletoes(Arceuthobiumspecies) of western North America also make excellent locations for roosting and nesting of the Northern Spotted Owlsand the Marbled Murrelets. In Australia the Diamond Firetailsand Painted Honeyeatersare recorded as nesting in different mistletoes. This behavior is probably far more widespread than currently recognized; more than 240 species of birds that nest in foliage in Australia have been recorded nesting in mistletoe, representing more than 75% of the resident avifauna.[citation needed]A study of mistletoe in junipersconcluded that more juniper berries sprout in stands where mistletoe is present, as the mistletoe attracts berry-eating birds which also eat juniper berries.[8]Such interactions lead to dramatic influences on diversity, as areas with greater mistletoe densities support higher diversities of animals. Thus, rather than being a pest, mistletoe can have a positive effect on biodiversity, providing high quality food and habitat for a broad range of animals in forests and woodlands worldwide.

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