Not to be confused with TOW missile, or Mistel, part of a German composite aircraft.
European mistletoe (Viscum album) attached to a dormant common aspen (Populus tremula)Mistletoe in an apple tree
Mistletoe is the common name for obligatehemiparasiticplants in the orderSantalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they extract water and nutrients from the host plant.
The name mistletoe originally referred to the species Viscum album (European mistletoe, of the family Santalaceae in the order Santalales); it is the only species native to the British Isles and much of Europe. A related species with red fruits, rather than white, Viscum cruciatum, occurs in Southwest Spain and Southern Portugal, as well as in Morocco in North Africa and in southern Africa.[1] There is also a wide variety of species in Australia.[2] The genus Viscum is not native to North America, but Viscum album was introduced to Northern California in 1900.[3][4]
European mistletoe has smooth-edged, oval, evergreen leaves borne in pairs along the woody stem, and waxy, white berries that it bears in clusters of two to six. The eastern mistletoe of North America is similar, but has shorter, broader leaves and longer clusters of ten or more berries.
Over the centuries, the term mistletoe has been broadened to include many other species of parasitic plants with similar habits, found in other parts of the world, that are classified in different genera and families such as the Misodendraceae of South America and the mainly southern hemisphere tropical Loranthaceae.
Online Etymology Dictionary claims a similar theory, noting: "The alteration of the ending... is perhaps from a mistaking of the final -n for a pluralsuffix after tan fell from use as a separate word, but Oxford finds it a natural evolution in West Saxon based on stress."[7]
The largest family of mistletoes, the Loranthaceae, has 73 genera and more than 900 species.[10]Subtropical and tropicalclimates have markedly more mistletoe species; Australia has 85, of which 71 are in Loranthaceae, and 14 in Santalaceae.[11]
Life cycle
Mistletoe species grow on a wide range of host trees, some of which experience side effects including reduced growth, stunting, and loss of infested outer branches. A heavy infestation may also kill the host plant. Viscum album successfully parasitizes more than 200 tree and shrub species.[citation needed]
All mistletoe species are hemiparasites because they do perform some photosynthesis for some period of their life cycle. However, in some species its contribution is very nearly zero. For example, some species, such as Viscum minimum, that parasitize succulents, commonly species of Cactaceae or Euphorbiaceae, grow largely within the host plant, with hardly more than the flower and fruit emerging. Once they have germinated and attached to the circulatory system of the host, their photosynthesis reduces so much that it becomes insignificant.[12]
Mistletoe in winter
Most of the Viscaceae bear evergreen leaves that photosynthesise effectively, and photosynthesis proceeds within their green, fleshy stems as well. Some species, such as Viscum capense, are adapted to semi-arid conditions and their leaves are vestigial scales, hardly visible without detailed morphological investigation. Therefore, their photosynthesis and transpiration only take place in their stems, limiting their demands on the water supply of its host, but also limiting their intake of carbon dioxide for photosynthesis. Accordingly, their contribution to the metabolic balance of its host becomes trivial and the idle parasite may become quite yellow or golden as it grows, having practically given up photosynthesis.[12]
At another extreme, other species have vigorous green leaves. Not only do they photosynthesize actively, but a heavy infestation of mistletoe plants may take over whole host tree branches, sometimes killing practically the entire crown and replacing it with their own growth. In such a tree the host is relegated purely to the supply of water and mineral nutrients and the physical support of the trunk. Such a tree may survive as a Viscum community for years; it resembles a totally unknown species unless one examines it closely, because its foliage does not look like that of any tree. An example of a species that behaves in this manner is Viscum continuum.[12]
A mistletoe seed germinates on the branch of a host tree or shrub, and in its early stages of development it is independent of its host. It commonly has two or even four embryos, each producing its hypocotyl, that grows toward the bark of the host under the influence of light and gravity, and potentially each forming a mistletoe plant in a clump. Possibly as an adaptation to assist in guiding the process of growing away from the light, the adhesive on the seed tends to darken the bark. On having made contact with the bark, the hypocotyl, with only a rudimentary scrap of root tissue at its tip, penetrates it, a process that may take a year or more. In the meantime the plant is dependent on its own photosynthesis. Only after it reaches the host's conductive tissue may it begin to rely on the host for its needs. Later, it forms a haustorium that penetrates the host tissue and takes water and nutrients from the host plant.[12]
Species more or less obligate include the leafless quintral, Tristerix aphyllus, which lives deep inside the sugar-transporting tissue of a spiny cactus, appearing only to show its tubular red flowers,[13] and the genus Arceuthobium (dwarf mistletoe; Santalaceae) that has reduced photosynthesis; as an adult, it manufactures only a small proportion of the sugars it needs from its own photosynthesis, but as a seedling actively photosynthesizes until a connection to the host is established.[citation needed]
Some species of the largest family, Loranthaceae, have small, insect-pollinated flowers (as with Santalaceae), but others have spectacularly showy, large, bird-pollinated flowers.[citation needed]
Most mistletoe seeds are spread by birds who eat the 'seeds' (in actuality drupes). Of the many bird species that feed on them, the mistle thrush is the best-known in Europe, the phainopepla in southwestern North America, and Dicaeumflowerpeckers in Asia and Australia. Depending on the species of mistletoe and the species of bird, the seeds are regurgitated from the crop, excreted in their droppings, or stuck to the bill and causing the bird to have to wipe it off onto a branch. The seeds are coated with a sticky material called viscin. Some viscin remains on the seed and when it touches a stem, it sticks tenaciously. The viscin soon hardens and attaches the seed firmly to its future host, where it germinates and its haustorium penetrates the sound bark.[14]
Specialist mistletoe eaters have adaptations that expedite the process; some pass the seeds through their unusually shaped digestive tracts so fast that a pause for defecation of the seeds is part of the feeding routine. Others have adapted patterns of feeding behavior; the bird grips the fruit in its bill and squeezes the sticky-coated seed out to the side. The seed sticks to the beak and the bird wipes it off onto the branch and consumes the remainder of the fruit.[15]
Once a mistletoe plant is established on its host, it usually is possible to save a valuable branch by pruning and judicious removal of the wood invaded by the haustorium, if the infection is caught early enough. Some species of mistletoe can regenerate if the pruning leaves any of the haustorium alive in the wood.[17][18]
Toxicity
There are 1500 species of mistletoe, varying widely in toxicity to humans; the European mistletoe (Viscum album) is more toxic than the American mistletoe (Phoradendron serotinum).[19][20]
The primary active toxic compounds in American mistletoe are phoratoxins (in Phoradendron) and their effects can include blurred vision, diarrhea, nausea, and vomiting, although these rarely occur.[20] Their primary mechanism of action is through disruption of cell membranes which causes lysis and cell death at high concentrations.[21]
In European mistletoe (Viscum), viscumin is the more dangerous active toxin. It acts by irreversibly inhibiting ribsomal protein synthesis in cells, which leads to the death of the affected cell, tissue damage in the area of exposure from mass cell death in the very short term, with the potential for organ failure and death depending on the level of exposure. Early symptoms depend mostly on the route of exposure as the first cells it contacts (thus the first to have their protein synthesis deactivated by it) will be the first to die. Its toxic effects take place through the same mechanism as ricin and other ribosome-inactivating proteins but it enters the cells by a different mechanism than ricin and is toxic even to cultured ricin-resistant cells.[22][23]
Mistletoes are often considered pests that kill trees and devalue natural habitats, but some species have recently been recognized as ecological keystone species, organisms that have a disproportionately pervasive influence over their community.[24] A broad array of animals depend on mistletoe for food, consuming the leaves and young shoots, transferring pollen between plants and dispersing the sticky seeds. In western North America their juicy berries are eaten and spread by birds (notably the phainopepla) while in Australia the mistletoebird behaves similarly. When eaten with the fruit, some seeds pass unharmed through their digestive systems, emerging in extremely sticky droppings which the bird deposits on tree branches, where some may stick long enough to germinate. As the plants mature, they grow into masses of branching stems that suggest the popular name "witches' brooms".[citation needed]
A study of mistletoe in junipers concluded that more juniper berries sprout in stands where mistletoe is present, as the mistletoe attracts berry-eating birds who also eat juniper berries.[25]
Mistletoe is relevant to several cultures. Pagan cultures regarded the white berries as symbols of male fertility, with the seeds resembling semen.[26] The Celts, particularly, saw mistletoe as the semen of Taranis, while the Ancient Greeks referred to mistletoe as "oak sperm".[27][28] Also in Roman mythology, mistletoe was used by the hero Aeneas to reach the underworld.[29][30]
Mistletoe may have played an important role in Druidic mythology in the Ritual of Oak and Mistletoe, although the only ancient writer to mention the use of mistletoe in this ceremony was Pliny. Evidence taken from bog bodies makes the Celtic use of mistletoe seem medicinal rather than ritual.[31] It is possible that mistletoe was originally associated with human sacrifice and only became associated with the white bull after the Romans banned human sacrifices.[32]
The Romans associated mistletoe with peace, love, and understanding and hung it over doorways to protect the household.[33]
In the advent of the Christian era, mistletoe in the Western world became associated with Christmas as a decoration under which lovers are expected to kiss, as well as with protection from witches and demons.[34] Mistletoe continued to be associated with fertility and vitality through the Middle Ages, and by the eighteenth century it had also become incorporated into Christmas celebrations around the world. The custom of kissing under the mistletoe is referred to as popular among servants in late eighteenth-century England.[35][36]
The serving class of Victorian England is credited with perpetuating the tradition.[37] The tradition dictated that a man was allowed to kiss any woman standing underneath mistletoe, and that bad luck would befall any woman who refused the kiss.[38][39] One variation on the tradition stated that with each kiss a berry was to be plucked from the mistletoe, and the kissing must stop after all the berries had been removed.[37][39]
From at least the mid-nineteenth century, Caribbean herbalists of African descent have referred to mistletoe as "god-bush".[40] In Nepal, diverse mistletoes are used for a variety of medical purposes, particularly for treating broken bones.[41]
Mistletoe is the floral emblem of the U.S. state of Oklahoma and the flower of the UK county of Herefordshire. Every year, the UK town of Tenbury Wells holds a mistletoe festival and crowns a 'Mistletoe Queen'.[33]
See also
Witch's broom, a growth of the host plant's own tissue, rather than a parasite in itself
The Santalales are an order of flowering plants in the dicotyledons. Well-known members of the Santalales include sandalwoods and the many species of mistletoes. The order has a cosmopolitan distribution, but is heavily concentrated in tropical and subtropical regions. It derives its name from its type genus, Santalum (sandalwood).
Viscaceae is a taxonomic family name of flowering plants. In this circumscription, the family includes the several genera of mistletoes. This family name is currently being studied and under review as in past decades, several systems of plant taxonomy recognized this family, notably the 1981 Cronquist system.
Loranthaceae, commonly known as the showy mistletoes, is a family of flowering plants. It consists of about 75 genera and 1,000 species of woody plants, many of them hemiparasites. The three terrestrial species are Nuytsia floribunda, Atkinsonia ligustrina, and Gaiadendron punctatum Loranthaceae are primarily xylem parasites, but their haustoria may sometimes tap the phloem, while Tristerix aphyllus is almost holoparasitic. For a more complete description of the Australian Loranthaceae, see Flora of Australia onlineArchived 2018-04-01 at the Wayback Machine., for the Malesian Loranthaceae see Flora of Malesia.
The Santalaceae, sandalwoods, are a widely distributed family of flowering plants which, like other members of Santalales, are partially parasitic on other plants. Its flowers are bisexual or, by abortion, unisexual. Modern treatments of the Santalaceae include the family Viscaceae (mistletoes), previously considered distinct.
In botany and mycology, a haustorium is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates the host's tissue and draws nutrients from it. In mycology, it refers to the appendage or portion of a parasitic fungus, which performs a similar function. Microscopic haustoria penetrate the host plant's cell wall and siphon nutrients from the space between the cell wall and plasma membrane but do not penetrate the membrane itself. Larger haustoria do this at the tissue level.
Viscum album is a species of mistletoe in the family Santalaceae, commonly known as European mistletoe, common mistletoe, or simply as mistletoe. It is native to Europe as well as to western and southern Asia. V. album is found only rarely in North America, as an introduced species.
Viscum is a genus of about 70–100 species of mistletoes, native to temperate and tropical regions of Europe, Africa, Asia and Australasia. Traditionally, the genus has been placed in its own family Viscaceae, but recent genetic research by the Angiosperm Phylogeny Group shows this family to be correctly placed within a larger circumscription of the sandalwood family, Santalaceae. Its name is the origin of the English word viscous, after the Latin viscum, a sticky bird lime made from the plants' berries.
Phoradendron is a genus of mistletoe, native to warm temperate and tropical regions of the Americas. The center of diversity is the Amazon rainforest. Phoradendron is the largest genus of mistletoe in the Americas, and possibly the largest genus of mistletoes in the world. Traditionally, the genus has been placed in the family Viscaceae, but recent genetic research acknowledged by the Angiosperm Phylogeny Group shows this family to be correctly placed within a larger circumscription of the sandalwood family, Santalaceae.
A parasitic plant is a plant that derives some or all of its nutritional requirements from another living plant. They make up about 1% of angiosperms and are found in almost every biome. All parasitic plants develop a specialized organ called the haustorium, which penetrates the host plant, connecting them to the host vasculature – either the xylem, phloem, or both. For example, plants like Striga or Rhinanthus connect only to the xylem, via xylem bridges (xylem-feeding). Alternately, plants like Cuscuta and some members of Orobanche connect to both the xylem and phloem of the host. This provides them with the ability to extract resources from the host. These resources can include water, nitrogen, carbon and/or sugars. Parasitic plants are classified depending on the location where the parasitic plant latches onto the host, the amount of nutrients it requires, and their photosynthetic capability. Some parasitic plants can locate their host plants by detecting volatile chemicals in the air or soil given off by host shoots or roots, respectively. About 4,500 species of parasitic plants in approximately 20 families of flowering plants are known.
Phoradendron leucarpum is a species of mistletoe in the Viscaceae family which is native to the United States and Mexico. Its common names include American mistletoe, eastern mistletoe, hairy mistletoe and oak mistletoe. It is native to Mexico and the continental United States. It is hemiparasitic, living in the branches of trees. The berries are white and 3–6 millimeters (0.12–0.24 in). It has opposite leaves that are leathery and thick. Ingesting the berries can cause "stomach and intestinal irritation with diarrhea, lowered blood pressure, and slow pulse". This shrub can grow to 1 meter (3.3 ft) by 1 meter (3.3 ft).
Phoradendron californicum, the desert mistletoe or mesquite mistletoe, is a hemiparasitic plant native to southern California, Nevada, Arizona, Sonora, Sinaloa and Baja California. It can be found in the Mojave and Sonoran Deserts at elevations of up to 1400 m.
Dendrophthoe falcata is one of the hemiparasitic plants that belong to the mistletoe family Loranthaceae. It is the most common of all the mistletoes that occur in India. At the moment reports say that it has around 401 plant hosts. The genus Dendrophthoe comprises about 31 species spread across tropical Africa, Asia, and Australia among which 7 species are found in India.
Osyris compressa is a facultatively hemiparasitic, mainly South African plant of the sandalwood family, Santalaceae. Until recently, the favoured binomial name was Colpoon compressum, but around 2001, the genus Colpoon was included in Osyris on the basis of comparative DNA studies. That assignment is not final, however, and according to the Kew Gardens plant list, Colpoon compressum P.J.Bergius, though still in review, is the accepted name.
Phoradendron tomentosum, the leafy mistletoe, hairy mistletoe or Christmas mistletoe, is a plant parasite. It is characterized by its larger leaves and smaller berries than dwarf mistletoe. Leafy mistletoe seldom kill but they do rob their hosts of moisture and some minerals, causing stress during drought and reducing crop productions on fruit and nut trees. Leafy mistletoe has the ability to photosynthesize on its own but it relies on other plants in order to obtain its nutrients. It attaches itself to a tree and then grows haustoria, in order to get the food and water it needs.
Lysiana exocarpi, commonly known as harlequin mistletoe, is a species of hemiparasitic shrub, endemic to Australia. It is in the Gondwanan family Loranthaceae and is probably the most derived genus of that family with 12 pairs of chromosomes. The Loranthaceae is the most diverse family in the mistletoe group with over 900 species worldwide and including the best known species in Australia. Mistletoes are notable for their relationships with other species. In an early reference to the group in Australia Allan Cunningham explorer and first Director of the Royal Botanic Gardens, Sydney, wrote in 1817: "The Bastard Box is frequently much encumbered with the twining adhering Loranthus aurantiacus which 'Scorning the soil, aloft she springs, Shakes her red plumes and claps her golden wings'."
Arceuthobium pusillum is a perennial, obligate parasitic plant in the sandalwood family. Its common names include Dwarf mistletoe or Eastern dwarf mistletoe. It is one of the most widespread dwarf mistletoes within its range which covers the eastern United States and Canada, from Saskatchewan to Nova Scotia and New Jersey. The species name "pusillum" derives from Latin "pusillus", meaning very small.
Viscum minimum is a species of mistletoe in the family Santalaceae. It is a parasitic plant native to South Africa.
Daniel Lee Nickrent is an American botanist, working in plant evolutionary biology, including the subdisciplines of genomics, phylogenetics, systematics, population genetics, and taxonomy. A major focus has been parasitic flowering plants, particularly of the sandalwood order (Santalales). His interest in photographic documentation and photographic databases has led to several photographic databases including Parasitic Plant Connection, Phytoimages, Plant Checklist for the Rocky Mountain National Park, and Plant Checklist for the Crab Orchard National Wildlife Refuge.
Phoratoxins are a group of peptide toxins that belong to the family of thionins, a subdivision of small plant toxins. Phoratoxins are proteins present in the leaves and branches of the Phoradendron, commonly known as the American variant of the mistletoe, a plant commonly used as decoration during the festive season. The berries of the mistletoe do not contain phoratoxins, making them less toxic compared to other parts of the plant. The toxicity of the mistletoe is dependent on the host tree, since mistletoe is known to be a semi-parasite. The host tree provides fixed inorganic nitrogen compounds necessary for the mistletoe to synthesize phoratoxins.
Amyema miraculosa, also known as the fleshy mistletoe and the round-leaf mistletoe, is an Australian native mistletoe found in all states except Tasmania. It is a woody, hemiparasitic plant, in the Loranthaceae family. Being hemiparasitic, it draws water and minerals from its host, however it photosynthesises to manufacture its own supply of carbohydrates.
1 2 "Mistletoe poisoning". MedlinePlus Medical Encyclopedia. National Library of Medicine. Retrieved 2 January 2025.
↑ Markman, Ofer; Rao, Usha; Lewis, Karen A.; Heffron, Gregory J.; Stec, Boguslaw; Teeter, Martha M. (1993). "Mode of Phospholipid Binding to the Membrane Active Plant Toxin Phoratoxin-A". New Developments in Lipid-Protein Interactions and Receptor Function: 263–274. doi:10.1007/978-1-4615-2860-9_25.
↑ Mosteller, Angie (2010). Christmas. First Printing. p.119.
↑ "When at Christmas in the hall / The men and maids are hopping, / If by chance I hear them bawl / Amongst them quick I pop in. / All the men, Jem, John, and Joe, / Cry, "What good luck has sent ye?" / And kiss beneath the mistletoe / The girl not turn'd of twenty...", song by George Colman the Younger in the musical comedy Two to One (1784)
↑ "The pendant mistletoe, hung up to view / Reminds the youth, the duty youth should do: / While titt'ring maidens, to enhance their wishes / Entice the men to smother them with kisses...", The Times (London), 24 December 1787 p.3 (poem), The Approach of Christmas.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
