seed plant
n.
A seed-bearing plant.
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For more information on seed plant, visit Britannica.com.
The noun has one meaning:
Meaning #1:
plant that reproduces by means of seeds not spores
Synonyms: spermatophyte, phanerogam
| Seed Plants Fossil range: ??? |
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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:
Seed-bearing plants were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetae, cycads, ginkgo, and conifers. Angiosperms are now thought to have evolved from a gymnosperm ancestor, which would make gymnosperms a paraphyletic group if it includes extinct taxa. Although not a monophyletic taxonomic unit, "gymnosperm" is still widely used to distinguish the four taxa of non-flowering, seed-bearing plants from the angiosperms.
Molecular phylogenies have conflicted with morphologically-based evidence as to whether extant gymnosperms comprise a monophyletic group. Some morphological data suggests that the Gnetophytes are the sister-group to angiosperms, but molecular phylogenies have generally shown a gymnosperm clade that includes the Gnetophytes as sister-group to the conifers.
A traditional classification grouped put all the seed plants in a single division, with classes for our five groups:
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.
A more modern classification ranks these groups as separate divisions (sometimes under the Superdivision Spermatophyta):
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Copyrights:
![]() | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved. Read more | |
![]() | Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved. Read more | |
![]() | WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. Read more | |
![]() | Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Spermatophyte". Read more |
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