Potamogeton

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Potamogeton
PotamogetonPerfoliatus2.jpg
Potamogeton perfoliatus
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
Order: Alismatales
Family: Potamogetonaceae
Genus: Potamogeton
L.
Species

80-100, see text

Potamogeton is a genus of aquatic, mostly freshwater, plants of the family Potamogetonaceae. Most are known by the common name pondweed, although many unrelated plants may be called pondweed, such as Canadian pondweed (Elodea canadensis). The genus name means "river neighbor", originating from the Greek potamos (river) and geiton (neighbor).[1][2]

Morphology[edit]

Potamogeton species range from large (stems of 6 m or more) to very small (less than 10 cm). Height is strongly influenced by environmental conditions, particularly water depth. All species are technically perennial, but some species disintegrate in autumn to a large number of asexually produced resting buds called turions, which serve both as a means of overwintering and dispersal. Turions may be borne on the rhizome, on the stem, or on stolons from the rhizome. Most species, however, persist by perennial creeping rhizomes. The leaves are alternate, which contrasts with the closely related genus Groenlandia, where the leaves are opposite or whorled.

In many species, all the leaves are submerged, and in these cases, they are typically thin and translucent. Some species, especially in ponds and very slow-moving waters, have floating leaves which tend to be opaque with a leathery texture.

All Potamogeton have a delicate membranous sheathing scale, the stipule, at the leaf axil. This may be wholly attached, partly attached, or free of the leaf, and it may have inrolled margins or appear as a tube. The morphology of the stipule is an important character for species identification. The flowers, which are often overlooked, are greenish-brown and are composed of four rounded segments borne in a spike.

Taxonomy[edit]

Potamogeton species are found throughout the world where is standing or running water occurs. In a detailed review of the genus, Wiegleb and Kaplan[3] recognised 69 species, but the variability of many species means that there is disagreement regarding the exact number of species. Curently, the number of accepted names is 94.[4] Hybridisation provides an added complexity to the taxonomy.

The genus has been split into several two subgenera, with several sections. Subgenus Potamogeton contains several Sections. Section Potamogeton contains the larger broad-leaved species such as P. natans, P. perfoliatus and P. alpinus.[5] Section Graminifolii consists of fine-leaved species such as P. rutilus, P. compressus and P. berchtoldii. Series Batrachoseris contains only one species, Potamogeton crispus.[5] Subgenus Coleogeton, containing P. pectinatus, P. filiformis and P. vaginatus, is now considered to belong to a separate genus, Stuckenia. These general divisions have been supported by molecular analysis.[6]

At least 27 hybrids have been observed in the British Isles alone,[5] and more than 50 worldwide,[3] of which 36 have been confirmed using genetic techniques.[7]

Taxonomic History[edit]

Several species of European pondweeds, including P. natans, P. lucens and P. crispus, were included in Linnaeus's Species Plantarum in 1753. Much of the European Potamogeton flora was subsequently named during the late 18th and early 19th century. As botanists ventured further afield, pondweeds began to be collected and named from other parts of the world. The North America flora was largely named by the start of the 20th century. Alfred Fryer became interested in Potamogeton in the 1880s, and was a recognised authority on the genus.[8] The first parts of his work The Potamogetons (Pond Weeds) of the British Isles were published in 1898. His death intervened, and the work was completed by Arthur Bennett (1843-1929), who named a large number of specimens sent to him from around the world. Robert Morgan (1863-1900) illustrated Fryer's contribution to the monograph, his colour plates drawing praise from later critics.[9][10]

New species continue to be described from less well-studied areas such as Asia and Africa, and it is possible that molecular analysis may reveal hitherto unknown cryptic species.

List of Potamogeton species[edit]

The following list is based on the mst up to date listing of valid Potamogeton taxa held on The Plant List.[4]

List of Potamogeton hybrids[edit]

List source :[4]

Ecology[edit]

Potamogeton species are found worldwide in many aquatic ecosystems. They are important as food and habitat for animals.[2][11] Most species are not weedy, but a few can become troublesome, such as curly-leaf pondweed (Potamogeton crispus).[12]

References[edit]

  1. ^ Thorne, R.F. (2012). "Jepson Manual treatment for Potamogetonaceae (Pondweed Family)". Jepson Manual Online. University & Jepson Herbaria; Regents of the University of California. Retrieved January 6, 2012. 
  2. ^ a b "Potamogeton". Flora of North America (eFloras) 22. Retrieved January 6, 2012. 
  3. ^ a b Wiegleb G., Kaplan Z. 1998. An account of the species of Potamogeton L. Folia Geobotanica, 33, 241-316
  4. ^ a b c "Potamogeton". The Plant List; Version 1.1 (published on the internet). Royal Botanic Gardens, Kew and Missouri Botanical Garden. 2010. Retrieved November 16, 2014. 
  5. ^ a b c Preston C.D. (1995). Pondweeds of Great Britain and Ireland. BSBI Handbook No. 8. Botanical Society of the British Isles, London.
  6. ^ Lindqvist C., De Laet J., Haynes R.R., Aagesen L., Keener B.R., Albert V.A. 2006. Molecular phylogenetics of an aquatic plant lineage, Potamogetonaceae. Cladistics, 22, 568-588.
  7. ^ Ito, Y., and Nr. Tanaka (2013) Additional Potamogeton hybrids from China: Evidence from a comparison of plastid trnTtrnF and nuclear ITS phylogenies. APG: Acta Phytotaxonomica et Geobotanica 64 (1): 1–14
  8. ^ Preston C.D. 1988. The Potamogeton L. species and hybrids described by Alfred Fryer. Watsonia, 17 23-35.
  9. ^ http://www.watsonia.org.uk/Wats16p217.pdf[dead link]
  10. ^ "Fryer, Alfred (1826 – 1912)". 
  11. ^ "Pondweeds: Potamogeton species". Center for Aquatic and Invasive Plants; University of Florida / IFAS. 2011. Retrieved January 6, 2012. 
  12. ^ "Curly leaf pondweed: Potamogeton crispus L.". Center for Invasive Species and Ecosystem Health. May 4, 2010. Retrieved January 6, 2012. 

External links[edit]