Pteridophyte

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A pteridophyte is a vascular plant (with xylem and phloem) that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are also referred to as "cryptogams", meaning that their means of reproduction is hidden. The pteridophytes include the ferns, horsetails, and the lycophytes (clubmosses, spikemosses, and quillworts). These are not a monophyletic group because ferns and horsetails are more closely related to seed plants than to the lycophytes. Therefore, "Pteridophyta" is no longer a widely accepted taxon, although the term pteridophyte remains in common parlance, as do pteridology and pteridologist as a science and its practitioner, to indicate lycophytes and ferns as an informal grouping, such as the International Association of Pteridologists and the Pteridophyte Phylogeny Group.

Description

Ferns and lycophytes (pteridophytes) are free-sporing vascular plants that have a life cycle with free-living, independent gametophyte and sporophyte phases. Their other common characteristics include vascular plant apomorphies (e.g., vascular tissue) and land plant plesiomorphies (e.g., spore dispersal and the absence of seeds).[1] [2]

Taxonomy

Phylogeny

Of the pteridophytes, ferns account for nearly 90% of the extant diversity.[2] Smith et al. (2006), the first higher-level pteridophyte classification published in the molecular phylogenetic era, considered the ferns as monilophytes, as follows:[3]

where the monilophytes comprise about 9,000 species, including horsetails (Equisetaceae), whisk ferns (Psilotaceae), and all eusporangiate and all leptosporangiate ferns. Historically both lycophytes and monilophytes were grouped together as pteridophytes (ferns and fern allies) on the basis of being spore-bearing ("seed-free"). In Smith's molecular phylogenetic study the ferns are characterised by lateral root origin in the endodermis, usually mesarch protoxylem in shoots, a pseudoendospore, plasmodial tapetum, and sperm cells with 30-1000 flagella.[3] The term "moniliform" as in Moniliformopses and monilophytes means "bead-shaped" and was introduced by Kenrick and Crane (1997)[4] as a scientific replacement for "fern" (including Equisetaceae) and became established by Pryer et al. (2004).[5] Christenhusz and Chase (2014) in their review of classification schemes provide a critique of this usage, which they discouraged as irrational. In fact the alternative name Filicopsida was already in use.[6] By comparison "lycopod" or lycophyte (club moss) means wolf-plant. The term "fern ally" included under Pteridophyta generally refers to vascular spore-bearing plants that are not ferns, including lycopods, horsetails, whisk ferns and water ferns (Marsileaceae, Salviniaceae and Ceratopteris), and even a much wider range of taxa. This is not a natural grouping but rather a convenient term for non-fern, and is also discouraged, as is eusporangiate for non-leptosporangiate ferns.[7]

However both Infradivision and Moniliformopses are also invalid names under the International Code of Botanical Nomenclature. Ferns, despite forming a monophyletic clade, are formally only considered as four classes (Psilotopsida; Equisetopsida; Marattiopsida; Polypodiopsida), 11 orders and 37 families, without assigning a higher taxonomic rank.[3]

Furthermore, within the Polypodiopsida, the largest grouping, a number of informal clades were recognised, including leptosporangiates, core leptosporangiates, polypods (Polypodiales), and eupolypods (including Eupolypods I and Eupolypods II).[3]

In 2014 Christenhusz and Chase, summarising the known knowledge at that time, treated this group as two separate unrelated taxa in a consensus classification;[7]

These subclasses correspond to Smith's four classes, with Ophioglossidae corresponding to Psilotopsida.

The two major groups previously included in Pteridophyta are phylogenetically related as follows:[7][8][9]

Tracheophyta – vascular plants

Lycopodiophyta

Euphyllophyta

Polypodiophyta – ferns

Spermatophyta – seed plants

Gymnospermae

Angiospermae – flowering plants

Subdivision

Pteridophytes consist of two separate but related classes, whose nomenclature has varied.[3][10] The terminology used by the Pteridophyte Phylogeny Group (2016)[2] (with some synonyms) is used here:

Classes, subclasses and orders

In addition to these living groups, several groups of pteridophytes are now extinct and known only from fossils. These groups include the Rhyniopsida, Zosterophyllopsida, Trimerophytopsida, the Lepidodendrales and the Progymnospermopsida.

Modern studies of the land plants agree that all pteridophytes share a common ancestor with seed plants. Therefore, pteridophytes do not form a clade but constitute a paraphyletic group.

Ecology

Pteridophyte life cycle

Just as with seed plants and mosses, the life cycle of pteridophytes involves alternation of generations. This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus, which produces gametes). Pteridophytes differ from mosses and seed plants in that both generations are independent and free-living, although the sporophyte is generally much larger and more conspicuous. The sexuality of pteridophyte gametophytes can be classified as follows:

  • Dioicous: each individual gametophyte is either male (producing antheridia and hence sperm) or female (producing archegonia and hence egg cells).
  • Monoicous: each individual gametophyte produces both antheridia and archegonia and can function both as a male and as a female.
    Protandrous: the antheridia mature before the archegonia (male first, then female).
    Protogynous: the archegonia mature before the antheridia (female first, then male).

These terms are not the same as monoecious and dioecious, which refer to whether a seed plant's sporophyte bears both male and female gametophytes, i. e., produces both pollen and seeds, or just one of the sexes.

See also

References

Bibliography

  • Cantino, Philip D.; Doyle, James A.; Graham, Sean W.; Judd, Walter S.; Olmstead, Richard G.; Soltis, Douglas E.; Soltis, Pamela S.; Donoghue, Michael J. (1 August 2007). "Towards a Phylogenetic Nomenclature of Tracheophyta". Taxon. 56 (3): 822. doi:10.2307/25065865.
  • Christenhusz, M. J. M.; Zhang, X. C.; Schneider, H. (18 February 2011). "A linear sequence of extant families and genera of lycophytes and ferns" (PDF). Phytotaxa. 19 (1): 7. doi:10.11646/phytotaxa.19.1.2.
  • Christenhusz, Maarten J.M. & Chase, Mark W. (2014). "Trends and concepts in fern classification". Annals of Botany. 113 (9): 571–594. doi:10.1093/aob/mct299. PMC 3936591. PMID 24532607.
  • Clark, James; Hidalgo, Oriane; Pellicer, Jaume; Liu, Hongmei; Marquardt, Jeannine; Robert, Yannis; Christenhusz, Maarten; Zhang, Shouzhou; Gibby, Mary; Leitch, Ilia J.; Schneider, Harald (May 2016). "Genome evolution of ferns: evidence for relative stasis of genome size across the fern phylogeny". New Phytologist. 210 (3): 1072–1082. doi:10.1111/nph.13833.
  • Chase, Mark W. & Reveal, James L. (2009). "A phylogenetic classification of the land plants to accompany APG III". Botanical Journal of the Linnean Society. 161 (2): 122–127. doi:10.1111/j.1095-8339.2009.01002.x.
  • Gifford, Ernest M.; Foster, Adriance S. (1996). Morphology and evolution of vascular plants (3rd ed.). New York: Freeman. ISBN 0-7167-1946-0.
  • Kenrick, Paul; Crane, Peter (1996). "Embryophytes: Land plants". Tree of Life Web Project. Retrieved 19 April 2017.
  • Kenrick, Paul; Crane, Peter R. (4 September 1997). "The origin and early evolution of plants on land" (PDF). Nature. 389 (6646): 33–39. doi:10.1038/37918.
  • Kenrick, Paul; Crane, Peter (1997). The Origin and Early Diversification of Land Plants: A Cladistic Study. Washington, D.C.: Smithsonian Institution Press. ISBN 9781560987291.
  • Pryer, K. M.; Schuettpelz, E.; Wolf, P. G.; Schneider, H.; Smith, A. R.; Cranfill, R. (1 October 2004). "Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences". American Journal of Botany. 91 (10): 1582–1598. doi:10.3732/ajb.91.10.1582.
  • Pteridophyte Phylogeny Group (November 2016). "A community-derived classification for extant lycophytes and ferns". Journal of Systematics and Evolution. 54 (6): 563–603. doi:10.1111/jse.12229.
  • Ranker, Tom A.; Haufler, Christopher H. (2008). Biology and Evolution of Ferns and Lycophytes. Cambridge University Press. ISBN 978-0-521-87411-3.
  • Raven, Peter H.; Evert, Ray F.; Eichhorn, Susan E. (2005). Biology of plants (7th ed.). New York, NY: Freeman and Company. ISBN 0-7167-1007-2.
  • Schneider, Harald; Schuettpelz, Eric (November 2016). "Systematics and evolution of lycophytes and ferns". Journal of Systematics and Evolution. 54 (6): 561–562. doi:10.1111/jse.12231.
  • Smith, Alan R.; Kathleen M. Pryer; Eric Schuettpelz; Petra Korall; Harald Schneider; Paul G. Wolf (2006). "A classification for extant ferns" (PDF). Taxon. 55 (3): 705–731. doi:10.2307/25065646. JSTOR 25065646.
  • Pteridophyte Phylogeny Group (November 2016). "A community-derived classification for extant lycophytes and ferns". Journal of Systematics and Evolution. 54 (6): 563–603. doi:10.1111/jse.12229.

External links

  • British Pteridological Society
  • Annual Review of Pteridological Research
  • Wikisource "Pteridophyta". Encyclopædia Britannica (11th ed.). 1911.
  • Pteridophytes Test Questions for Papers And Quizzes [Important]
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