Gnetophyta 238281 220373359 2008-06-19T15:26:14Z DOI bot 6652755 Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{Taxobox | name = Gnetophyta | image = Welwitchia.jpg | image_width = 240px | image_caption = ''[[Welwitschia mirabilis]]'' | regnum = [[Plant]]ae | divisio = '''Gnetophyta''' | classis = '''Gnetopsida''' | subdivision_ranks = Genera | subdivision = *''[[Gnetum]]'' *''[[Welwitschia]]'' *''[[Ephedra (genus)|Ephedra]]'' }} The [[plant]] division '''Gnetophyta''' or gnetophytes comprise three related families of [[woody plant]]s grouped in the [[gymnosperm]]s. The gnetophytes differ from other gymnosperms in having [[vessel element]]s as in the [[flowering plant]]s ('''Angiosperms''' or '''Magnoliophytes'''). The living Gnetophyta comprise three genera: *''[[Gnetum]]'' *''[[Welwitschia]]'' *''[[Ephedra (genus)|Ephedra]]'' ''[[Gnetum]]'' species are mostly [[wood]]y [[Vine|climbers]] in tropical forests. However, the most well-known member of this group, ''[[Gnetum gnemon]]'', is a tree. Its seeds are used to produce a crispy ''[[krupuk]]'' snack known as ''emping'' or ''krupuk belinjo''. ''[[Welwitschia]]'' comprises only one species, ''Welwitschia mirabilis''. It grows only in the deserts of [[Namibia]] and [[Angola]]. The plant is strange in having only two large strap-like leaves for all its life. These grow continuously from the base, and are usually tattered at the ends by flapping in the winds. Plants of the genus ''[[Ephedra (genus)|Ephedra]]'' are known as jointfirs because they have long slender branches which bear tiny scale-like leaves at their nodes. ''Ephedra'' has been traditionally used as a [[stimulant]], but is a [[controlled substance]] today in many juristictions because of the risk of harmful or even fatal [[overdose|overdosing]]. In some classifications all three genera are placed in a single order (Gnetales) but in others distributed among three orders, each containing a single family and genus. ''Gnetum'' and ''Welwitschia'' diverged from each other more recently than from ''Ephedra''.<ref name="crane">{{cite journal | url = http://www.amjbot.org/cgi/content/full/91/10/1683 | title = Fossils and plant phylogeny | author = Peter R. Crane, Patrick Herendeen and Else Marie Friis | journal = American Journal of Botany | year = 2004 | volume = 91 | pages = 1683–1699 | doi = 10.3732/ajb.91.10.1683 }}</ref> Knowledge of fossils of the gnetophytes has increased greatly since the 1980s.<ref name="crane"/> There are fossils from the [[Permian]],<ref>{{cite journal | url = http://aob.oxfordjournals.org/cgi/content/full/94/2/281 | title = A New Permian Gnetalean Cone as Fossil Evidence for Supporting Current Molecular Phylogeny | author = Zi-Qiang Wang | journal = Annals of Botany | year = 2004 | volume = 94 | issue = 2 | pages = 281–288 | doi = 10.1093/aob/mch138 | pmid = 15229124 }}</ref> the [[Triassic]], and the [[Jurassic]] which may belong to the gnetophytes, but this is uncertain.<ref name="rydin">{{cite journal | url = http://aob.oxfordjournals.org/cgi/content/full/98/1/123 | journal = Annals of Botany | year = 2006 | volume = 98 | issue = 1 | pages = 123–140 | doi = 10.1093/aob/mcl078 | title = Former Diversity of Ephedra (Gnetales): Evidence from Early Cretaceous Seeds from Portugal and North America | author = Catarina Rydin, Kaj Raunsgaard Pedersen, Peter R. Crane and Else Marie Friis | pmid = 16675607}}</ref> The fossil record is richer starting in the early [[Cretaceous]], with fossils of plants as well as [[seed]]s and [[pollen]] which can be clearly assigned to the gnetophytes.<ref name="rydin"/> Molecular phylogenies of extant gymnosperms have conflicted with morphological characters with regard to whether the gymnosperms as a whole (including gnetophytes) comprise a [[monophyletic group]] or a [[paraphyletic]] one that gave rise to angiosperms. At issue is whether the Gnetophyta are the [[sister group]] of [[angiosperms]], or whether they are sister to, or nested within, other extant gymnosperms. Numerous fossil gymnosperm clades once existed that are morphologically at least as distinctive as the four living [[gymnosperm]] groups, such as [[Bennettitales]], ''Caytonia'' and the glossopterids. When these gymnosperm fossils are considered the question of gnetophyte relationships to other seed plants becomes even more complicated. == References == <references/> *Burleigh, J. G., and S. Mathews. 2004. Phylogenetic signal in nucleotide data from seed plants: implications for resolving the seed plant tree of life. ''American Journal of Botany'' 91: 1599-1613 ([http://www.amjbot.org/cgi/content/abstract/91/10/1599 abstract]) *Gifford, Ernest M., Adriance S. Foster. 1989. Morphology and Evolution of Vascular Plants. Third edition. WH Freeman and Company, New York. *Hilton, Jason, and Richard M. Bateman. 2006. Pteridosperms are the backbone of seed-plant phylogeny. ''Journal of the Torrey Botanical Society'' 133: 119-168 ([http://www.bioone.org/perlserv/?request=get-abstract&doi=10.3159%2F1095-5674(2006)133%5B119%3APATBOS%5D2.0.CO%3B2&ct=1 abstract]) [[Category:Gnetophyta| ]] [[ar:شعبة الجنتويات]] [[bg:Гнетови]] [[da:Gnetophyta]] [[de:Gnetopsida]] [[es:Gnetophyta]] [[fr:Gnetales]] [[it:Gnetophyta]] [[he:גנטאים]] [[lt:Gnetūnai]] [[hu:Leplesmagvúak]] [[ja:グネツム綱]] [[pl:Gniotowe]] [[pt:Gnetófita]] [[ro:Gnetatae]] [[ru:Гнетовые]] [[sk:Lianovcorasty]] [[fi:Gnetophytina]] [[sv:Gnetophyta]] [[vi:Ngành Dây gắm]] [[to:ʻakau sukau]] [[uk:Гнетоподібні]] [[zh:买麻藤纲]]