Gymnosperm

Not to be confused with the flowering plant genera Gymnosperma and Gymnospermium.

Gymnosperm
Temporal range: Carboniferous–Present
Various gymnosperms.
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Spermatophytes
Clade: Gymnospermae
Living orders[1]

The gymnosperms (/ˈdʒɪmnəˌspɜːrmz, -noʊ-/ ⓘ JIM-nə-spurmz, -⁠noh-; lit. 'revealed seeds') are a group of seed-producing plants that include conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae. The term gymnosperm comes from the composite word in Greek: γυμνόσπερμος (γυμνός, gymnos, 'naked' and σπέρμα, sperma, 'seed'), and literally means 'naked seeds'. The name is based on the unenclosed condition of their seeds (called ovules in their unfertilized state). The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or on their own as in yew, Torreya, and Ginkgo.[2] The life cycle of a gymnosperm involves alternation of generations, with a dominant diploid sporophyte phase, and a reduced haploid gametophyte phase, which is dependent on the sporophytic phase. The term "gymnosperm" is often used in paleobotany to refer to (the paraphyletic group of) all non-angiosperm seed plants. In that case, to specify the modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used.

The gymnosperms and angiosperms together constitute the spermatophytes or seed plants. The spermatophytes are subdivided into five divisions, the angiosperms and four divisions of gymnosperms: the Cycadophyta, Ginkgophyta, Gnetophyta, and Pinophyta (also known as Coniferophyta). Newer classification place the gnetophytes among the conifers.[3] Numerous extinct seed plant groups are recognised including those considered pteridosperms/seed ferns, as well other groups like the Bennettitales.[4]

By far the largest group of living gymnosperms are the conifers (pines, cypresses, and relatives), followed by cycads, gnetophytes (Gnetum, Ephedra and Welwitschia), and Ginkgo biloba (a single living species). About 65% of gymnosperms are dioecious,[5] but conifers are almost all monoecious.[6]

Some genera have mycorrhiza, fungal associations with roots (Pinus), while in some others (Cycas) small specialised roots called coralloid roots are associated with nitrogen-fixing cyanobacteria.

  1. ^ Cite error: The named reference Phylogenomics of gymnosperms was invoked but never defined (see the help page).
  2. ^ "Gymnosperms on The Plant List". Theplantlist.org. Archived from the original on 2013-08-24. Retrieved 2013-07-24.
  3. ^ Yang, Yong; Ferguson, David Kay; Liu, Bing; Mao, Kang-Shan; Gao, Lian-Ming; Zhang, Shou-Zhou; Wan, Tao; Rushforth, Keith; Zhang, Zhi-Xiang (2022-07-01). "Recent advances on phylogenomics of gymnosperms and a new classification". Plant Diversity. 44 (4): 340–350. Bibcode:2022PlDiv..44..340Y. doi:10.1016/j.pld.2022.05.003. ISSN 2468-2659. PMC 9363647. PMID 35967253.
  4. ^ Raven, P.H. (2013). Biology of Plants. New York: W.H. Freeman and Co.
  5. ^ Walas, Łukasz; Mandryk, Wojciech; Thomas, Peter A.; Tyrała-Wierucka, Żanna; Iszkuło, Grzegorz (2018-09-01). "Sexual systems in gymnosperms: A review". Basic and Applied Ecology. 31: 1–9. Bibcode:2018BApEc..31....1W. doi:10.1016/j.baae.2018.05.009. ISSN 1439-1791. S2CID 90740232.
  6. ^ Walas Ł, Mandryk W, Thomas PA, Tyrała-Wierucka Ż, Iszkuło G (2018). "Sexual systems in gymnosperms: A review" (PDF). Basic and Applied Ecology. 31: 1–9. Bibcode:2018BApEc..31....1W. doi:10.1016/j.baae.2018.05.009. S2CID 90740232.