Spermatophyte

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Seed plants
Temporal range: Carboniferous? or earlier to present, 319–0 Ma
PinusSylvestris.jpg
Scots pine, Pinus sylvestris, a member of the Pinophyta
Scientific classification edit
Clade: Tracheophytes
Clade: Spermatophytes
Divisions
Synonyms
  • Phanerogamae

The spermatophytes, also known as phanerogams or phenogamae, comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or land plants. The term phanerogams or phanerogamae is derived from the Greek φανερός, phanerós meaning "visible", in contrast to the cryptogamae from Greek κρυπτός kryptós = "hidden" together with the suffix γαμέω, gameein, "to marry". These terms distinguished those plants with hidden sexual organs (cryptogamae) from those with visible sexual organs (phanerogamae).

Description

The extant spermatophytes form five divisions, the first four of which are traditionally grouped as gymnosperms, plants that have unenclosed, "naked seeds":

The fifth extant division is the flowering plants, also known as angiosperms or magnoliophytes, the largest and most diverse group of spermatophytes. Angiosperms possess seeds enclosed in a fruit, unlike gymnosperms.

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.

Evolution

A whole genome duplication event in the ancestor of seed plants occurred about 319 million years ago.[1] This gave rise to a series of evolutionary changes that resulted in the origin of seed plants.

A middle Devonian (385-million-year-old) precursor to seed plants from Belgium has been identified predating the earliest seed plants by about 20 million years. Runcaria, small and radially symmetrical, is an integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the mutlilobed integument. It is suspected that the extension was involved in anemophilous (wind) pollination. Runcaria sheds new light on the sequence of character acquisition leading to the seed. Runcaria has all of the qualities of seed plants except for a solid seed coat and a system to guide the pollen to the seed.[2]

Relationships and nomenclature

Seed-bearing plants were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetophytes, cycads, ginkgo, and conifers. Older morphological studies believed in a close relationship between the gnetophytes and the angiosperms,[3] in particular based on vessel elements. However, molecular studies (and some more recent morphological[4][5] and fossil[6] 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:[7][8][9]

angiosperms (flowering plants)

gymnosperms

cycads [10]

Ginkgo

Pinaceae (the pine family)

gnetophytes

other conifers

However, the relationships between these groups should not be considered settled.[3][11]

Other classifications group all the seed plants in a single division, with classes for the five groups:

A more modern classification ranks these groups as separate divisions (sometimes under the Superdivision Spermatophyta):

An alternative phylogeny of spermatophytes based on the work by Novíkov & Barabaš-Krasni 2015[12] with plant taxon authors from Anderson, Anderson & Cleal 2007[13] showing the relationship of extinct clades.

Spermatophytina

Moresnetiopsida Doweld 2001  

Lyginopteridopsida Novák 1961 emend. Anderson, Anderson & Cleal 2007

Pachytestopsida Doweld 2001

Callistophytales Rothwell 1981 emend. Anderson, Anderson & Cleal 2007

Peltaspermopsida Doweld 2001

Umkomasiales Doweld 2001  

Acrogymnospermae

Cycadopsida (Cycads)

Ginkgoopsida (Maidenhair trees)

Pinopsida (Conifers)

Phasmatocycadopsida Doweld 2001

Pentoxylopsida Pant ex Doweld 2001

Dictyopteridiopsida Doweld 2001

Cycadeoideopsida Scott 1923

Caytoniopsida Thomas ex Frenguelli 1946

Magnoliopsida (Flowering plants)

Unassigned spermatophytes:[citation needed]

References

  1. ^ Jiao Y, Wickett NJ, Ayyampalayam S, Chanderbali AS, Landherr L, Ralph PE, Tomsho LP, Hu Y, Liang H, Soltis PS, Soltis DE, Clifton SW, Schlarbaum SE, Schuster SC, Ma H, Leebens-Mack J, Depamphilis CW (2011) Ancestral polyploidy in seed plants and angiosperms. Nature
  2. ^ "Science Magazine". Runcaria, a Middle Devonian Seed Plant Precursor. American Association for the Advancement of Science. 2011. Retrieved March 22, 2011.
  3. ^ a b Palmer, Jeffrey D.; Soltis, Douglas E.; Chase, Mark W. (2004). "The plant tree of life: an overview and some points of view". American Journal of Botany. 91 (10): 1437–1445. doi:10.3732/ajb.91.10.1437. PMID 21652302.
  4. ^ James A. Doyle (January 2006). "Seed ferns and the origin of angiosperms". The Journal of the Torrey Botanical Society. 133 (1): 169–209. doi:10.3159/1095-5674(2006)133[169:SFATOO]2.0.CO;2. ISSN 1095-5674.
  5. ^ Coiro, Mario; Chomicki, Guillaume; Doyle, James A. (n.d.). "Experimental signal dissection and method sensitivity analyses reaffirm the potential of fossils and morphology in the resolution of the relationship of angiosperms and Gnetales". Paleobiology: 1–21. doi:10.1017/pab.2018.23. ISSN 0094-8373.
  6. ^ 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:10.1093/aob/mch138. PMC 4242163. PMID 15229124.
  7. ^ Chaw, Shu-Miaw; Parkinson, Christopher L.; Cheng, Yuchang; Vincent, Thomas M.; Palmer, Jeffrey D. (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 (8): 4086–4091. doi:10.1073/pnas.97.8.4086. PMC 18157. PMID 10760277.
  8. ^ Bowe, L. M.; Michelle, L.; Coat, Gwénaële; Claude (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 (8): 4092–4097. doi:10.1073/pnas.97.8.4092. PMC 18159. PMID 10760278.
  9. ^ Soltis, Douglas E.; Soltis, Pamela S.; Zanis, Michael J. (2002). "Phylogeny of seed plants based on evidence from eight genes". American Journal of Botany. 89 (10): 1670–1681. doi:10.3732/ajb.89.10.1670. PMID 21665594. Archived from the original on 2012-07-10.
  10. ^ 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:10.1093/molbev/msm059. PMID 17383970.
  11. ^ 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:10.1080/10635150600812619. PMID 16969937.
  12. ^ Novíkov & Barabaš-Krasni (2015). "Modern plant systematics". Liga-Pres: 685. doi:10.13140/RG.2.1.4745.6164. ISBN 978-966-397-276-3.
  13. ^ Anderson, Anderson & Cleal (2007). "Brief history of the gymnosperms: classification, biodiversity, phytogeography and ecology". Strelitzia. SANBI. 20: 280. ISBN 978-1-919976-39-6.

Bibliography

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