Spermatophyte
| Seed Plants Fossil range: Devonian? or earlier to recent |
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 Welwitschia mirabilis a member of the Gnetophyta
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The spermatophytes (from the Greek word "Σπερματόφυτα") (also known as phanerogams) comprise those plants that produce seeds. They are a subset of the embryophytes or land plants. The living spermatophytes form five groups:
- cycads, a subtropical and tropical group of plants with a large crown of compound leaves and a stout trunk,
- Ginkgo, a single living species of tree,
- conifers, cone-bearing trees and shrubs,
- gnetophytes, woody plants in the genera Gnetum, Welwitschia, and 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 gigantopterids.
Relationships and nomenclature
- Further information: Evolutionary history of plants
Seed-bearing plants were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetophytes, cycads, ginkgo, and conifers. Older morphological studies have shown a close relationship between the gnetophytes and the angiosperms,[1] in particular based on vessel elements. However, molecular studies (and some more recent morphological[2] and fossil[3] papers) have generally shown a clade of gymnosperms, 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:[4][5][6]
| gymnosperms |
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The relationships between these groups should not be considered settled.[1][8]
A traditional classification grouped put all the seed plants in a single division, with classes for our five groups:
- Division Spermatophyta
- Cycadopsida, the cycads
- Ginkgoopsida, the ginkgo
- Pinopsida, the conifers, ("Coniferopsida")
- Gnetopsida, the gnetophytes
- Magnoliopsida, the flowering plants, or Angiospermopsida
A more modern classification ranks these groups as separate divisions (sometimes under the Superdivision Spermatophyta):
- Cycadophyta, the cycads
- Ginkgophyta, the ginkgo
- Pinophyta, the conifers
- Gnetophyta, the gnetophytes
- Magnoliophyta, the flowering plants
References
- ↑ 1.0 1.1 Jeffrey D. Palmer, Douglas E. Soltis and Mark W. Chase (2004). "The plant tree of life: an overview and some points of view". American Journal of Botany 91: 1437–1445. doi:. http://www.amjbot.org/cgi/content/full/91/10/1437.
- ↑ James A. Doyle (January 2006). "Seed ferns and the origin of angiosperms". The Journal of the Torrey Botanical Society 133 (1): 169–209. doi:. doi:10.3159/1095-5674(2006)133%5B169:SFATOO%5D2.0.CO;2.
- ↑ Zi-Qiang Wang (2004). "A New Permian Gnetalean Cone as Fossil Evidence for Supporting Current Molecular Phylogeny". Annals of Botany 94 (2): 281–288. doi:. PMID 15229124. http://aob.oxfordjournals.org/cgi/content/full/94/2/281.
- ↑ Chaw, Shu-Miaw, Christopher L. Parkinson, Yuchang Cheng, Thomas M. Vincent, and Jeffrey D. Palmer. 2000. 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
- ↑ Bowe, L. Michelle, Gwénaële Coat, and Claude W. dePamphilis. 2000. 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.
- ↑ Soltis, Douglas E., Pamela S. Soltis and Michael J. Zanis. 2002. Phylogeny of seed plants based on evidence from eight genes. American Journal of Botany 89: 1670-1681.
- ↑ Chung-Shien Wu, Ya-Nan Wang, Shu-Mei Liu and Shu-Miaw Chaw (2007). "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". Molecular Biology and Evolution 24 (6): 1366–1379. doi:. PMID 17383970.
- ↑ Won, Hyosig; Renner, Susanne (August 2006). "Dating Dispersal and Radiation in the Gymnosperm Gnetum (Gnetales)—Clock Calibration When Outgroup Relationships Are Uncertain". Systematic Biology 55 (4): 610–622. doi:.