Gymnosperm
290236
223402561
2008-07-03T22:43:41Z
205.124.145.254
{{nofootnotes}}
{{Taxobox
| name = Gymnosperms
| image = Fichtennadel.jpg
| image_width = 220px
| image_caption = [[White Spruce]] leaves (needles)
| regnum = [[Plant]]ae
| subdivision_ranks = [[Division (biology)|Divisions]]
| subdivision =
[[Pinophyta]] (or Coniferophyta) - Conifers<br>
[[Ginkgo|Ginkgophyta]] - ''Ginkgo''<br>
[[Cycad|Cycadophyta]] - Cycads<br>
[[Gnetophyta]] - ''Gnetum, Ephedra, Welwitschia''
}}
'''Gymnosperm''' (Gymnospermae) are a group of [[spermatophyte]] seed-bearing [[plant]]s with [[ovule]]s on the edge or blade of an open [[sporophyll]], which are usually arranged in cone-like structures. The other major group of seed-bearing plants, the [[angiosperms]], have ovules enclosed in a [[carpel]], a sporophyll with fused margins. The term gymnosperm comes from the Greek word ''gumnospermos'', meaning "naked seeds" and referring to the unenclosed condition of the seeds, as when they are produced they are found naked on the scales of a cone or similar structure. There are between 700 and 900 species of Gymnosperm. Often they are used for many economical uses and as folk medicines. Some common uses for them are [[soap]], [[varnish]], [[lumber]], [[paint]], edible plants, and [[perfume]]s.
Gymnosperms are [[heterosporous]], producing ''[[microspores]]'' that develop into [[pollen]] grains and ''[[megaspores]]'' that are retained in an ovule. After fertilization (joining of the micro- and megaspore), the resulting embryo, along with other cells comprising the ovule, develops into a seed. The seed is a sporophyte resting stage. Reproduction in gymnosperms varies greatly. [[Cycad]]s and ''[[Ginkgo]]'' have motile sperm that swim directly to the egg inside the ovule, while [[conifer]]s and [[gnetophyte]]s have sperm with no [[flagella]] that are conveyed to the egg along a [[pollen tube]] which grows through ovule tissue.
[[Image:Pseudotsuga menziesii cone.jpg|left|thumb|[[Coast Douglas-fir]] cone]]
In early classification schemes, the gymnosperms (Gymnospermae) "naked seed" plants were regarded as a "natural" group. However, certain fossil discoveries suggest that the angiosperms evolved from a gymnosperm ancestor, which would make the gymnosperms a [[paraphyletic]] group if all extinct taxa are included. Modern [[cladistics]] only accepts taxa that are [[monophyletic]], traceable to a common ancestor and inclusive of all descendants of that common ancestor. So, while the term 'gymnosperm' is still widely used for non-angiosperm seed-bearing plants, the plant species once treated as gymnosperms are usually distributed among four groups, which can be given equal rank as divisions within the Kingdom Plantae.
Molecular [[phylogeny|phylogenies]] of extant gymnosperms have conflicted with morphological datasets with regard to whether they 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 [[clade]]s once existed that are morphologically at least as distinctive as the four living gymnosperm groups, such as [[Bennettitales]], ''Caytonia'' and the glossopterids. When these groups are considered the question of gymnosperm and angiosperm relationships 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])
== External links ==
{{commons|Gymnosperm}}
*[http://www.conifers.org/ Gymnosperm Database]
*[http://www.huh.harvard.edu/research/mathews-lab/atolHtmlSite/ Gymnosperms on the Tree of Life]
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{{Botany}}
[[Category:Gymnosperms|*]]
[[Category:Plant taxonomy| sort31 Gymnospermae]]
[[ar:عاريات البذور]]
[[ca:Gimnosperma]]
[[cs:Nahosemenné]]
[[da:Nøgenfrøede]]
[[de:Nacktsamige Pflanzen]]
[[el:Γυμνόσπερμο]]
[[es:Gymnospermae]]
[[eo:Gimnospermoj]]
[[fa:بازدانگان]]
[[fr:Gymnospermes]]
[[gl:Ximnosperma]]
[[ko:겉씨식물]]
[[id:Tumbuhan berbiji terbuka]]
[[it:Gymnospermae]]
[[he:חשופי זרע]]
[[hu:Nyitvatermők]]
[[mk:Голосеменици]]
[[nah:Petlāuhxinachtli]]
[[nl:Naaktzadigen]]
[[ja:裸子植物]]
[[no:Nakenfrøede planter]]
[[pl:Nagonasienne]]
[[pt:Gymnospermas]]
[[qu:Llat'an muruyuq]]
[[ru:Голосеменные]]
[[simple:Gymnosperm]]
[[sk:Nahosemenné rastliny]]
[[sl:Golosemenke]]
[[sv:Nakenfröiga växter]]
[[ta:வித்துமூடியிலி]]
[[te:వివృతబీజాలు]]
[[vi:Thực vật hạt trần]]
[[tr:Açık tohumlular]]
[[uk:Голонасінні]]
[[zh:裸子植物]]