関: Viscum album

WordNet

American plants closely resembling Old World mistletoe (同)false mistletoe
shrub of central and southeastern Europe; partially parasitic on beeches, chestnuts and oaks (同)Loranthus europaeus
Old World parasitic shrub having branching greenish stems with leathery leaves and waxy white glutinous berries; the traditional mistletoe of Christmas (同)Viscum_album, Old World mistletoe

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European mistletoe attached to a silver birch

Mistletoe is the common name for most obligate hemiparasitic plants in the order Santalales. These plants attach to and penetrate the branches of a tree or shrub by a structure called the haustorium, through which they absorb 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 was the only species native to Great Britain and much of Europe. A separate species, Viscum cruciatum, occurs in Southwest Spain and Southern Portugal, as well as North Africa, Australia and Asia.

Over the centuries, the term 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 even families — such as the Misodendraceae and the Loranthaceae.

In particular, the Eastern mistletoe native to North America, Phoradendron leucarpum, belongs to a distinct genus of the Santalaceae family. The genus Viscum is not native to North America, but Viscum album has been introduced to California.^[1] 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 10 or more berries.

Etymology

The word 'mistletoe' derives from the older form 'mistle', adding the Old English word tān (twig). 'Mistle' is common Germanic (Old High German mistil, Middle High German. mistel, Old English mistel, Old Norse mistil).^[2] Further etymology is uncertain, but may be related to the Germanic base for 'mash'.^[3]

Mistletoe groups

Parasitism has evolved at least twelve times among the vascular plants;^[4] and of those, the parasitic mistletoe habit has evolved independently five times, in the Misodendraceae, Loranthaceae, and Santalaceae, including the former separate families Eremolepidaceae and Viscaceae. Although Viscaceae and Eremolepidaceae were placed in a broadly defined Santalaceae by Angiosperm Phylogeny Group II, DNA data indicate they evolved independently.^{[citation needed]}

The largest family of mistletoes, the Loranthaceae, has 73 genera and over 900 species.^[5] Subtropical and tropical climates have markedly more mistletoe species; Australia has 85, of which 71 are in Loranthaceae, and 14 in Santalaceae.^[6]

Life cycle

Mistletoe in winter

Mistletoe plants grow on a wide range of host trees; they commonly reduce their growth and a large plant stunts and commonly kills the distal portion of branch it grows on. A heavy infestation may kill the entire host plant. Viscum album successfully parasitises more than 200 tree and shrub species.

Technically, all mistletoe species are hemiparasites, because they do perform at least a little photosynthesis for at least a short period of their life cycle. However, this is academic in some species whose contribution is very nearly zero. For example, some species, such as Viscum minimum, that parasitise 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 far that its becomes insignificant.^[7]

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 host's supply of water, but also limiting their intake of carbon dioxide for photosynthesis. Accordingly their contribution to the host's metabolic balance becomes trivial and the idle parasite may become quite yellow as it grows, having practically given up photosynthesis.^[7]

At another extreme other species have vigorous green leaves. Not only do they photosynthesise 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 like that is Viscum continuum.^[7]

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 towards 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 mean time the plant is dependent on its own photosynthesis. Only after it reaches the host's conductive tissue can 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.^[7]

Species more or less completely parasitic 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,^[8] and the genus Arceuthobium (dwarf mistletoe; Santalaceae) which 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.

Some species of the largest family, Loranthaceae, have small, insect-pollinated flowers (as with Santalaceae), but others have spectacularly showy, large, bird-pollinated flowers.

Most mistletoe seeds are spread by birds that eat the (drupes). Quite a range of birds feed on them, of which the mistle thrush is the best-known in Europe, the Phainopepla in southwestern North America, and Dicaeum of 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, from which the bird wipes it onto a suitable 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.^[9]

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 behaviour; 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.^[10]

Biochemically, viscin is a complex adhesive mix containing cellulosic strands and mucopolysaccharides.^[11]

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.^[12]^[13]

Ecological importance

Mistletoe 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.^[14] 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 Phainopepla, or silky-flycatcher). When eaten, some seeds pass unharmed through their digestive systems; if the birds’ droppings happen to land on a suitable branch, the seeds may stick long enough to germinate. As the plants mature, they grow into masses of branching stems which suggest the popular name "witches’ brooms". The dense evergreen witches' brooms formed by the dwarf mistletoes (Arceuthobium species) of western North America also make excellent locations for roosting and nesting of the northern spotted owl and the marbled murrelet. In Australia the diamond firetail and painted honeyeater are 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 birds.^{[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 which also eat juniper berries.^[15] 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.

Cultural references

Mistletoe is relevant to several cultures. It is associated with Western Christmas as a decoration, under which lovers are expected to kiss. The reasons for this are less than clear. It is clear that Mistletoe has played an important role in Druidic mythology. Most interesting is the Ritual of Oak and Mistletoe.

In Norse Mythology, Loki tricked the blind god Hodur into murdering Balder with an arrow made of Mistletoe, being the only plant to which Balder was vulnerable. Some versions of the story have mistletoe becoming a symbol of peace and friendship to compensate for its part in the murder.^[16]

Images

European mistletoe on an apple tree in Essex, England
Mistletoe bush on a Eucalyptus tree
Mistletoe attached to Eucalyptus host
Fruits
Red mistletoe, New Zealand
Mistletoe in San Bernardino Mountains
Mistletoe berries in Wye Valley
Mistletoe in abundance in Wye Valley
Mistletoe in North Central Texas
Desert mistletoe on a palo verde tree in southern Arizona.

References

^ USDA, NRCS. 2009. The PLANTS Database (http://plants.usda.gov, 28 August 2009). National Plant Data Center, Baton Rouge, LA 70874-4490 USA
^ Grimm, Jacob and Wilhelm. "Deutsches Wörterbuch". Woerterbuchnetz. Retrieved November 30, 2014.
^ Oxford English Dictionary, 3rd edition, December 2000
^ JH Westwood, JI Yoder, MP Timko, CW dePhamphilis (2010) The evolution of parasitism in plants. Trends Plant Sci 15:227-235
^ WS Judd, CS Campbell, EA Kellogg, PF Stevens & MJ Donaghue (2002) Plant systematics: a phylogenetic approach. Sinauer Associates, Inc., Sunderland Massachusetts, USA. ISBN 0-87893-403-0
^ B.A. Barlow (1983) A revision of the Viscaceae of Australia. Brunonia 6, 25–58.
^ ^a ^b ^c ^d Visser, Johann (1981). South African parasitic flowering plants. Cape Town: Juta. ISBN 0-7021-1228-3.
^ Susan Milius, "Botany under the Mistletoe" Science News' 158.26/27 (December 2000:412).
^ Zulu Journal. University of California Press. pp. 114–. GGKEY:5QX6L53RH1U. Retrieved 17 May 2013.
^ Maurice Burton; Robert Burton (2002). International Wildlife Encyclopedia. Marshall Cavendish. pp. 869–. ISBN 978-0-7614-7266-7. Retrieved 17 May 2013.
^ International Society for Horticultural Science. Section for Ornamental Plants; International Society for Horticultural Science. Commission on Landscape and Urban Horticulture; International Society for Horticultural Science. Working Group on New Ornamentals (2009). Proceedings of the VIth International Symposium on New Floricultural Crops: Funchal, Portugal, June 11–15, 2007. International Society for Horticultural Science. ISBN 978-90-6605-200-0. Retrieved 17 May 2013.
^ "Mistletoe". University of California - Davis. Retrieved November 30, 2014.
^ Torngren, T. S., E. J. Perry, and C. L. Elmore. 1980. Mistletoe Control in Shade Trees. Oakland: Univ. Calif. Agric. Nat. Res. Leaflet 2571
^ David M. Watson, "Mistletoe-A Keystone Resource in Forests and Woodlands Worldwide" Annual Review of Ecology and Systematics 32 (2001:219–249).
^ Susan Milius, "Mistletoe, of All Things, Helps Juniper Trees" Science News 161.1 (January 2002:6).
^ "Norse, Greek & Roman mistletoe traditions". The Mistletoe Pages. Retrieved 4 February 2015.

External links

About mistletoe
Parasitic Plant Connection. See families Misodendraceae, Loranthaceae, Santalaceae, and Viscaceae
Introduction to Parasitic Flowering Plants by Nickrent & Musselman
Phoradendron serotinum images at bioimages.vanderbilt.edu
Scientific Studies, Research and Clinical Trials on Mistletoe Treatment in Cancer
Deck the halls with wild, wonderful mistletoe, West Virginia Department of Agriculture
"Mistletoe". Encyclopaedia Britannica 16 (9th ed.). 1883.

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English Journal

Spatiotemporal mutualistic model of mistletoes and birds.

Wang C1, Liu R, Shi J, Del Rio CM.Author information 1Department of Mathematics, University of Wyoming, Laramie, WY, 82071, USA.AbstractA mathematical model which incorporates the spatial dispersal and interaction dynamics of mistletoes and birds is derived and studied to gain insights of the spatial heterogeneity in abundance of mistletoes. Fickian diffusion and chemotaxis are used to model the random movement of birds and the aggregation of birds due to the attraction of mistletoes, respectively. The spread of mistletoes by birds is expressed by a dispersal operator, which is typically a convolution integral with a dispersal kernel. Two different types of kernel functions are used to study the model, one is a Dirac delta function which reflects the special case that the spread behavior is local, and the other one is a general non-negative symmetric function which describes the nonlocal spread of mistletoes. When the kernel function is taken as the Dirac delta function, the threshold condition for the existence of mistletoes is given and explored in terms of parameters. For the general non-negative symmetric kernel case, we prove the existence and stability of spatially nonhomogeneous equilibria. Numerical simulations are conducted by taking specific forms of kernel functions. Our study shows that the spatial heterogeneous patterns of mistletoes are related to the specific dispersal pattern of birds which carry mistletoe seeds.
Journal of mathematical biology.J Math Biol.2014 May;68(6):1479-520. doi: 10.1007/s00285-013-0664-8. Epub 2013 Apr 19.
A mathematical model which incorporates the spatial dispersal and interaction dynamics of mistletoes and birds is derived and studied to gain insights of the spatial heterogeneity in abundance of mistletoes. Fickian diffusion and chemotaxis are used to model the random movement of birds and the aggr
PMID 23604589

Korean mistletoe (Viscum album coloratum) extract extends the lifespan of nematodes and fruit flies.

Lee SH1, An HS, Jung YW, Lee EJ, Lee HY, Choi ES, An SW, Son H, Lee SJ, Kim JB, Min KJ.Author information 1Department of Biological Sciences, Inha University, Inchon, 402-751, Korea.AbstractViscum album coloratum (Korean mistletoe) is a semi-parasitic plant that grows on various trees and has a variety of biological functions such as immunomodulation, apoptosis, and anti-tumor activity. In this study, we investigated the effects of Korean mistletoe extract (KME) on lifespan in experimental models using Caenorhabditis elegans and Drosophila melanogaster. Supplementation of KME at 50 μg/ml extended the mean survival time by 9.61 and 19.86 % in worms and flies, respectively. The longevity benefit of KME was not due to reduced feeding, reproduction, and/or locomotion in flies and worms. The supplementation of KME also did not increase resistance to various stresses including heat shock, oxidative, or starvation stresses. Furthermore, KME did not further extend the lifespan of flies fed a dietary restricted diet but did increase the expression of Sir2, one of the target genes of dietary restriction, suggesting that KME may function as a putative dietary restriction mimetic. These results also suggest that the longevity promoting effects of KME may be an example of mild stress-induced hormesis.
Biogerontology.Biogerontology.2014 Apr;15(2):153-64. doi: 10.1007/s10522-013-9487-7. Epub 2013 Dec 14.
Viscum album coloratum (Korean mistletoe) is a semi-parasitic plant that grows on various trees and has a variety of biological functions such as immunomodulation, apoptosis, and anti-tumor activity. In this study, we investigated the effects of Korean mistletoe extract (KME) on lifespan in experime
PMID 24337961

Nectar secretion dynamic links pollinator behavior to consequences for plant reproductive success in the ornithophilous mistletoe Psittacanthus robustus.

Guerra TJ1, Galetto L, Silva WR.Author information 1Programa de Pós-Graduação em Ecologia, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil.AbstractThe mistletoe Psittacanthus robustus was studied as a model to link flower phenology and nectar secretion strategy to pollinator behaviour and the reproductive consequences for the plant. The bright-coloured flowers presented diurnal anthesis, opened asynchronously throughout the rainy season and produced copious dilute nectar as the main reward for pollinators. Most nectar was secreted just after flower opening, with little sugar replenishment after experimental removals. During the second day of anthesis in bagged flowers, the flowers quickly reabsorbed the offered nectar. Low values of nectar standing crop recorded in open flowers can be linked with high visitation rates by bird pollinators. Eight hummingbirds and two passerines were observed as potential pollinators. The most frequent flower visitors were the hummingbirds Eupetomena macroura and Colibri serrirostris, which actively defended flowering mistletoes. The spatial separation between anthers, stigma and nectar chamber promotes pollen deposition on flapping wings of hovering hummingbirds that usually probe many flowers per visit. Seed set did not differ between hand-, self- and cross-pollinated flowers, but these treatments set significantly more seeds than flowers naturally exposed to flower visitors. We suggest that the limitation observed in the reproductive success of this plant is not related to pollinator scarcity, but probably to the extreme frequency of visitation by territorial hummingbirds. We conclude that the costs and benefits of plant reproduction depend on the interaction strength between flowers and pollinators, and the assessment of nectar secretion dynamics, pollinator behaviour and plant breeding system allows clarification of the complexity of such associations.
Plant biology (Stuttgart, Germany).Plant Biol (Stuttg).2014 Mar 18. doi: 10.1111/plb.12146. [Epub ahead of print]
The mistletoe Psittacanthus robustus was studied as a model to link flower phenology and nectar secretion strategy to pollinator behaviour and the reproductive consequences for the plant. The bright-coloured flowers presented diurnal anthesis, opened asynchronously throughout the rainy season and pr
PMID 24641568

Japanese Journal

Antioxidant Activity and Phenolic Content of Mistletoe Extracts Following High-Temperature Batch Extraction

Rahmawati Siti Irma,Ishimaru Kanji,Hou De-Xing,Hayashi Nobuyuki
Food Science and Technology Research 20(2), 201-206, 2014
… Mistletoe is a traditional medicinal plant containing bioactive phenolic compounds with, for example, anti-cancer effects. … oortiana showing a high antioxidant activity of 51 µmol TEAC/g extract as well as high content of phenolic compounds (289 mg GAE/g extract) among the mistletoe extracts obtained by HTBE. … other phenolic compounds such as catechin, epicatechin, rutin and quercetin partly contributed to the antioxidant effect of mistletoe extracts obtained by HTBE. …
NAID 130004463414

The Identification of in Vitro Production of Lectin from Callus Cultures of Korean Mistletoe (Viscum album L. var. coloratum)

LEE Keun Pyo,LEE Dae Won
Bioscience, biotechnology, and biochemistry 77(4), 884-887, 2013-04-23
… Despite potential medical, economical, and agronomical importance, the bioprocessing of mistletoe cell cultures, from callus cultures to mass production of high-value products (e.g., lectins and viscotoxins), has been unsuccessful to date. … In this study, we confirmed the potential of in vitro lectin production from callus cultures of Korean mistletoe (Viscum album L. …
NAID 10031170741