Viscum is a genus of over 100 species of , native to temperate and tropical regions of Europe, Africa, Asia and Australasia.
They are woody, Parasitic plant with branches long. Their hosts are woody shrubs and . The foliage is dichotomously or verticillately branching, with opposite pairs or whorls of green leaf which perform some photosynthesis (minimal in some species, notably V. nudum), but with the plant drawing its mineral and water needs from the host tree. Different species of Viscum tend to use different host species; most species are able to use several different host species.
The are inconspicuous, greenish-yellow, diameter. The fruit is a berry, white, yellow, orange, or red when mature, containing one or more embedded in very sticky juice; the seeds are dispersed when (notably the mistle thrush) eat the fruit, and remove the sticky seeds from the bill by wiping them on tree branches where they can germinate.
Toxicity in the genus Viscum
Viscum species are poisonous to humans; eating the fruit causes a weak pulse and acute gastrointestinal problems including stomach pain and
diarrhea.
At least one of the active ingredients is the
lectin viscumin, which is intensely toxic. It inhibits protein synthesis by catalytically inactivating
ribosomes.
[Sjur Olsnes, Fiorenzo Stirpe, Kirsten Sandvig, Alexander Pihl. Isolation and Characterization of Viscumin, a Toxic Lectin from Viscum album L. THE JOURNAL OF BIOLOGICAL CHEMISTRY Vol. 257, No 22, November 25, pp. 13263-13270, 1982.] In spite of this, many species of animals are adapted to eating the fruit as a significant part of their diet.
[David M. Watson, "Mistletoe-A Keystone Resource in Forests and Woodlands Worldwide" Annual Review of Ecology and Systematics 32 (2001:219–249).]
Fossil record
†
Viscum morlotii from the early
Miocene, has been described from
fossil leaf compressions that have been found in the Kristina Mine at Hrádek nad Nisou in
North Bohemia, the
Czech Republic.
[A review of the early Miocene Mastixioid flora of the Kristina Mine at Hrádek nad Nisou in North Bohemia, The Czech Republic, January 2012 by F. Holý, Z. Kvaček and Vasilis Teodoridis - ACTA MUSEI NATIONALIS PRAGAE Series B – Historia Naturalis • vol. 68 • 2012 • no. 3–4 • pp. 53–118]
Species
112 species are accepted.
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Other sources
