The

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Arceuthobium'', commonly called dwarf

mistletoe Mistletoe is the common name for obligate parasite, obligate parasitic plant, hemiparasitic plants in the Order (biology), order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they ...

s, is a genus of 42 species of

parasitic plant 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 Parasite, parasitic plants develop a specialized organ ...

s that parasitize members of

Pinaceae The Pinaceae (), or pine family, are conifer trees or shrubs, including many of the well-known conifers of commercial importance such as Cedrus, cedars, firs, Tsuga, hemlocks, Pinyon_pine, piñons, larches, pines and spruces. The family is incl ...

and

Cupressaceae Cupressaceae or the cypress family is a family of conifers. The family includes 27–30 genera (17 monotypic), which include the junipers and redwoods, with about 130–140 species in total. They are monoecious, subdioecious or (rarely) dioecio ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, and

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

. Of the 42 species that have been recognized, 39 and 21 of these are endemic to North America and the United States, respectively. They all have very reduced shoots and

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

(mostly reduced to scales) with the bulk of the plant living under the host's bark. Recently the number of species within the genus has been reduced to 26 as a result of more detailed genetic analysis.

Description

They are

dioecious Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...

, individual plants being either male or female. The

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

is unusual in that it builds up hydrostatic pressure internally when ripe and shoots the single sticky

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

up to speeds nearly , an example of rapid plant movement. The lodgepole pine dwarf mistletoe,'' Arceuthobium americanum, has been found to explosively-disperse its seeds through

thermogenesis Thermogenesis is the process of heat production in organisms. It occurs in all warm-blooded animals, and also in a few species of thermogenic plants such as the Eastern skunk cabbage, the Voodoo lily ('' Sauromatum venosum''), and the giant w ...

.
Rolena A.J. deBruyn, Mark Paetkau, Kelly A. Ross, David V. Godfrey & Cynthia Ross Friedman. Thermogenesis-triggered seed dispersal in dwarf mistletoe. Dwarf mistletoe seeds are enveloped in a

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

, glue-like substance called

viscin {{Short pages monitor A standardized system called the Hawksworth 6-class dwarf mistletoe rating (DMR) system has been devised to determine how much dwarf mistletoe has infected a tree. To use this system, the living part of the

tree crown The crown of a plant is the total of an individual plant's aboveground parts, including stems, leaves, and reproductive structures. A plant community canopy consists of one or more plant crowns growing in a given area. The crown of a woody pla ...

needs to be broken up into 3 sections, (top, middle, bottom). Each section is then rated either 0, 1, or 2 with a score of 0 being assigned for a uninfected section, 1 for light infection with fewer than half of the branches infected, or 2 for heavy infection with over half of the branches infected. The 3 numbers are then added together to give the total rating for the tree.

Species

Arceuthobium occidentale on Pinus sabiniana

* '' Arceuthobium abietinum'' Engelm. ex Munz * '' Arceuthobium americanum'' Nutt. ex Engelm. * '' Arceuthobium apachecum'' Hawksworth & Wiens * '' Arceuthobium azoricum'' Hawksw. & Wiens * '' Arceuthobium blumeri'' A. Nels. * '' Arceuthobium californicum'' Hawksworth & Wiens * '' Arceuthobium campylopodum'' Engelm. * '' Arceuthobium cyanocarpum'' (A. Nels. ex Rydb.) A. Nels. * '' Arceuthobium divaricatum'' Engelm. * '' Arceuthobium douglasii'' Engelm. * '' Arceuthobium gillii'' Hawksworth & Wiens * '' Arceuthobium globosum'' Hawksw. & Wiens * '' Arceuthobium laricis'' (Piper) St. John * '' Arceuthobium littorum'' Hawksworth, Wiens & Nickrent * '' Arceuthobium microcarpum'' (Engelm.) Hawksworth & Wiens * '' Arceuthobium minutissimum'' Hook. f. * '' Arceuthobium monticola'' Hawksworth, Wiens & Nickrent * '' Arceuthobium occidentale'' Engelm. * '' Arceuthobium oxycedri'' (DC.) M.Bieb. * '' Arceuthobium pusillum'' Peck * '' Arceuthobium siskiyouense'' Hawksworth, Wiens & Nickrent * '' Arceuthobium tsugense'' (Rosendahl) G.N. Jones * '' Arceuthobium vaginatum'' (Humb. & Bonpl. ex Willd.) J. Presl (Syn. ''Viscum vaginatum'' Humb. & Bonpl. ex Willd.)

References

External links

Maleshoots of ''A. campylopodum'' in California

Fruiting plant of ''A. campylopodum'' on Pine shoot

PLANTS profile for Arceuthobium (United States) including range maps.

US forest service data about dwarf mistletoes
{{Taxonbar, from=Q244255 Dioecious plants Epiphytes Parasitic plants Santalaceae genera

Description

Species

References

Further reading

External links