Spermatophyte
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2008-06-21T14:28:36Z
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{{Taxobox
| name = Seed Plants
| image = Welwitchia.jpg
| image_width = 200px
| image_caption = ''Welwitschia mirabilis'' a member of the [[Gnetophyta]]
| fossil_range = ???
| regnum = [[Plant]]ae
| subdivision_ranks = '''Divisions'''
| subdivision =
*[[Pinophyta]]
*[[Cycad|Cycadophyta]]
*[[Ginkgo|Ginkgophyta]]
*[[Gnetophyta]]
*[[Flowering plant|Magnoliophyta]]
*[[Bennettitales]][[extinction|†]]
}}
The '''spermatophytes''' (from the Greek word "Σπερματόφυτα") (also known as '''phanerogams''') comprise those [[plant]]s that produce [[seed]]s. They are a subset of the [[embryophyte]]s or land plants. The living spermatophytes form five groups:
*[[cycad]]s, a subtropical and tropical group of plants with a large crown of compound leaves and a stout trunk,
*''[[Ginkgo]]'', a single species of [[tree]],
*[[conifers]], cone-bearing trees and [[shrub]]s,
*[[gnetophytes]], [[woody plant]]s in the genera ''[[Gnetum]]'', ''[[Welwitschia]]'', and ''[[Ephedra (genus)|Ephedra]]'', and
*[[angiosperms]], the flowering plants, a large group including many familiar plants in a wide variety of habitats.
In addition to the taxa listed above, the fossil record contains evidence of many [[extinct]] taxa of seed plants. The so-called "seed ferns" ([[Pteridospermae]]) were one of the earliest successful groups of land plants, and forests dominated by seed ferns were prevalent in the late [[Paleozoic]]. ''[[Glossopteris]]'' was the most prominent [[tree]] [[genus]] in the ancient southern [[supercontinent]] of [[Gondwana]] during the [[Permian]] period. By the [[Triassic]] period, seed ferns had declined in ecological importance, and representatives of modern gymnosperm groups were abundant and dominant through the end of the [[Cretaceous]], when angiosperms radiated. Another Late Paleozoic group of probable spermatophytes were the [[gigantopterid]]s.
==Relationships and nomenclature==
{{see|Evolutionary history of plants}}
Seed-bearing plants were traditionally divided into [[angiosperm]]s, or flowering plants, and [[gymnosperm]]s, which includes the gnetophytes, cycads, ginkgo, and conifers. Older morphological studies have shown a close relationship between the gnetophytes and the angiosperms,<ref name="palmer">{{cite journal | url = http://www.amjbot.org/cgi/content/full/91/10/1437 | title = The plant tree of life: an overview and some points of view | author = Jeffrey D. Palmer, Douglas E. Soltis and Mark W. Chase | journal = American Journal of Botany | year = 2004 | volume = 91 | pages = 1437–1445 | doi = 10.3732/ajb.91.10.1437}}</ref> in particular based on [[vessel elements]]. However, molecular studies (and some more recent morphological<ref>{{cite journal | journal = The Journal of the Torrey Botanical Society | pages = 169–209 | title = Seed ferns and the origin of angiosperms | author = James A. Doyle | volume = 133 | issue = 1 | date = January 2006 | id = {{doi | id = 10.3159/1095-5674(2006)133%5B169:SFATOO%5D2.0.CO;2 | label = <nowiki>10.3159/1095-5674(2006)133[169:SFATOO]2.0.CO;2</nowiki> }} | year = 2006 | doi = 10.3159/1095-5674(2006)133[169:SFATOO]2.0.CO;2 }}</ref> and fossil<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> papers) have generally shown a [[clade]] of [[gymnosperm]]s, with the gnetophytes in or near the conifers. For example, one common proposed set of relationships is known as the ''gne-pine hypothesis'' and looks like:<ref>Chaw, Shu-Miaw, Christopher L. Parkinson, Yuchang Cheng, Thomas M. Vincent, and Jeffrey D. Palmer. 2000. [http://www.pnas.org/cgi/content/full/97/8/4086 Seed plant phylogeny inferred from all three plant genomes: Monophyly of extant gymnosperms and origin of Gnetales from conifers]. ''Proceedings of the National Academy of Sciences'' 97: 4086-4091
</ref><ref>Bowe, L. Michelle, Gwénaële Coat, and Claude W. dePamphilis. 2000. [http://www.pnas.org/cgi/content/full/97/8/4092 Phylogeny of seed plants based on all three genomic compartments: Extant gymnosperms are monophyletic and Gnetales' closest relatives are conifers]. ''[[Proceedings of the National Academy of Sciences]]'' 97: 4092-4097.</ref><ref>Soltis, Douglas E., Pamela S. Soltis and Michael J. Zanis. 2002. [http://intl.amjbot.org/cgi/content/full/89/10/1670 Phylogeny of seed plants based on evidence from eight genes]. ''[[American Journal of Botany]]'' 89: 1670-1681.</ref>
{{clade |
1=[[angiosperm]]s |
label2=[[gymnosperm]]s |
2={{clade |
1=[[cycad]]s <ref>{{cite journal | journal = Molecular Biology and Evolution | year = 2007 | volume = 24 | issue =6 | pages = 1366–1379 | doi = 10.1093/molbev/msm059 | title = Chloroplast Genome (cpDNA) of Cycas taitungensis and 56 cp Protein-Coding Genes of Gnetum parvifolium: Insights into cpDNA Evolution and Phylogeny of Extant Seed Plants | author = Chung-Shien Wu, Ya-Nan Wang, Shu-Mei Liu and Shu-Miaw Chaw | pmid = 17383970 }}</ref> |
2=''[[Ginkgo]]'' |
3={{clade |
1={{clade |
1=[[Pinaceae]] (the pine family) |
2=[[gnetophytes]]
}} |
2=other conifers
}}
}}
}}
The relationships between these groups should not be considered settled.<ref name="palmer"/><ref>{{cite journal | title = Dating Dispersal and Radiation in the Gymnosperm Gnetum (Gnetales)—Clock Calibration When Outgroup Relationships Are Uncertain | author = Won, Hyosig; Renner, Susanne | journal = Systematic Biology | volume = 55 | issue = 4 | date = August 2006 | pages = 610–622 | doi = 10.1080/10635150600812619 }}</ref>
A traditional classification{{Specify|date=February 2008}} grouped put all the seed plants in a single [[division (biology)|division]], with [[class (taxonomy)|class]]es for our five groups:
*Division '''Spermatophyta'''
**'''[[Cycad|Cycadopsida]]''', the cycads
**'''[[Ginkgo|Ginkgoopsida]]''', the ginkgo
**'''[[Pinopsida]]''', the conifers, ("Coniferopsida")
**'''[[Gnetophytes|Gnetopsida]]''', the gnetophytes
**'''[[Magnoliopsida]]''', the [[flowering plant]]s, or '''Angiospermopsida'''
A more modern classification ranks these groups as separate divisions (sometimes under the '''Superdivision Spermatophyta'''):
*'''[[Cycad|Cycadophyta]]''', the cycads
*'''[[Ginkgo|Ginkgophyta]]''', the ginkgo
*'''[[Pinophyta]]''', the [[conifer]]s
*'''[[Gnetophytes|Gnetophyta]]''', the gnetophytes
*'''[[Flowering plant|Magnoliophyta]]''', the [[flowering plant]]s
== References ==
<references/>
[[Category:Plants]]
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