View source for Biology:Potamogeton obtusifolius

{{Short description|Species of aquatic plant}}
{{speciesbox
|image = Potamogeton obtusifolius kz1.JPG
|genus = Potamogeton
|species = obtusifolius
|authority = Mert. & W.D.J.Koch
|synonyms = 
*''Buccaferrea obtusifolia'' <small>(Mert. & W.D.J.Koch) Bubani</small>
*''Potamogeton divaricatus'' <small>Wolfg.</small>
*''Potamogeton liljebladii'' <small>Wallman ex Rchb.</small>
*''Potamogeton tataricus'' <small>Less.</small>
*''Potamogeton reflexus'' <small>A.Benn.</small>
*''Spirillus obtusifolius'' <small>(Mert. & W.D.J.Koch) Nieuwl.</small>
|synonyms_ref = <ref name=kwc2/>
}}

'''''Potamogeton obtusifolius''''', known as '''blunt-leaved pondweed''',<ref name=BSBI07/> is an [[Biology:Aquatic plant|aquatic plant]] in the [[Biology:Genus|genus]] ''Potamogeton''. It grows mainly in mesotrophic to eutrophic lakes, ponds and ditches, rarely in brackish water. It occurs primarily in Central Europe, the British Isles, Fennoscandia and eastern North America.

==Description==
Blunt-leaved pondweed grows annually from [[Biology:Turion (botany)|turions]] and seed, producing branching plants with slender, flattened stems that have well-developed nodal glands (these appear as two raised bumps on the stem where the leaf attaches). The submerged leaves are long, rather grass-like, sessile, translucent leaves that are 48–85 (rarely up to 100)&nbsp;mm long and 1.5–3.55&nbsp;mm wide and pale green, often with a very marked reddish or brownish tinge<ref name=Preston/> and a pink tinge along the midrib. There are 1–2 lateral veins either side of the midrib. As the name suggests, the leaf tips are rather blunt,<ref name=Preston/> though close inspection usually reveals a narrow point at the tip. The [[Biology:Stipule|stipule]]s are open. There are no rhizomes or floating leaves. Abundant turions are produced along the stem, especially in autumn as the plant disintegrates.

The flower spikes of blunt-leaved pondweed are rather short and dense, 4–9&nbsp;mm long with 6–8 flowers in each.<ref name=Preston/> Fruits, which are approximately 3 × 2&nbsp;mm, are freely produced.

Blunt-leaved pondweed could be confused with other fine-leaved pondweeds within its range, especially ''[[Biology:Potamogeton berchtoldii|Potamogeton berchtoldii]]'' and ''P. friesii'',<ref name=Preston/> but potentially also ''[[Biology:Potamogeton pusillus|P. pusillus]]''. The combination of open stipules, rounded tips to the leaves, dense flower spikes and a tendency to produce a mass of bushy growth at the surface all help to distinguish this plant, but use of a botanical key or flora is recommended.

''Potamogeton obtusifolius'' is diploid, with 2n=26.<ref name=Kap2/>

According to a key monograph on the genus, no hybrids of ''Potamogeton obtusifolius'' have been confirmed.<ref name=Wiegleb/> However, ''P''. × ''saxonicus'' <small>Hagstr.</small> has been suggested to be the hybrid with ''P. pusillus''.<ref name=kwc2/>

==Taxonomy==
Blunt-leaved pondweed was first described in 1823 by Franz Carl Mertens and Wilhelm Daniel Joseph Koch.<ref name=kwc2/> The specific name ''obtusifolius'' means 'blunt-leaved'. It is related to other fine-leaved pondweeds, such as ''P. friesii'' and ''P. pusillus''.

Wang et al.<ref name=Wang/>  have suggestedbbased on DNA analysis that ''P. obtusifolius'' may have arisen through hybridisation between ''[[Biology:Potamogeton compressus|P. compressus]]'' and ''P. pusillus''.

==Distribution==
''Potamogeton obtusifolius'' has a wide global distribution, occurring in North America (Canada, northern US),<ref name=USDA/> Europe (Scandinavia, Central Europe, N Balkans, Great Britain, Ireland, France, N Spain),<ref name=Sweden/> Asia (NE China (Heilongjiang Province), Russia, Japan, Kazakhstan, Kyrgyzstan, Mongolia, Myanmar, Caucasus, Iran).<ref name=Guo/>

==Ecology and conservation==
In Britain, ''P. obtusifolius'' occurs in a range of standing water habitats including ponds, ditches, canals<ref name='Briggs'/> and shallow lakes, favouring circumneutral or slightly acidic waters.<ref name='Preston'/> It is strictly a lowland plant and rarely observed in running water, except where current speeds are very slow. Although widely distributed it has a patchy distribution and is not usually abundant at any individual site. Like other fine-leaved pondweeds, ''P. obtusifolius'' probably benefits from a certain amount of disturbance to suppress competing vegetation. It seems to favour smaller water bodies and apparently tolerates poor water quality, including turbid water, reasonably well. In spite of this, blunt-leaved pondweed does not usually proliferate in eutrophic lakes. It is possible that this species is rather sensitive to wind action.

In cultivation, ''P. obtusifolius'' leaves were eaten by three different species of chironomid (non-biting midge) larvae.<ref name=Moore/>

Globally and in various national Red Lists, blunt-leaved pondweed is considered Least Concern.<ref name=IUCN/> However, blunt-leaved pondweed has suffered local declines and is Critically Endangered in Switzerland, Vulnerable in Germany,<ref name=IUCN/> Very Rare in Luxemburg,<ref name=Colling/> listed as Endangered in New Jersey and Pennsylvania, and Sensitive in Washington.<ref name=USDA/>

It is considered to have declined in Britain, but is still widespread,<ref name=NewAt/> and listed as Least Concern.<ref name=Cheffings/>

==Cultivation==
Blunt-leaved pondweed is not presently in cultivation. Although its wide ecological tolerance suggests it may not be difficult to grow, it would probably require a deeper substrate than is usual in most ponds. It can also be grown in aquaria by anchoring the turions in sand or mud.<ref name=Moore/> It is also likely to compete poorly with other pond plants.{{citation needed|date=November 2014}}

==References==
{{Reflist|3|refs=
<ref name='Briggs'>[http://archive.bsbi.org.uk/WBull45.pdf Briggs J.D., Tandy C.E. 1987. Aquatic Plants in the Montgomery Canal. BSBI Welsh Bulletin, 45, 3-5] {{webarchive|url=https://web.archive.org/web/20121015232944/http://archive.bsbi.org.uk/WBull45.pdf |date=2012-10-15}}</ref>
<ref name=BSBI07>{{BSBI 2007|accessdate=2014-10-17}}</ref>
<ref name=Cheffings>Cheffings, C.M.; Farrell, L. (eds), Dines, T.D.; Jones, R.A.; Leach, S.J.; McKean, D.R.; Pearman, D.A.; Preston, C.D.; Rumsey, F.J.; Taylor, I. (2005). [http://jncc.defra.gov.uk/pdf/pub05_speciesstatusvpredlist3_web.pdf "The Vascular Plant Red Data List for Great Britain"]. ''Species Status'' '''7''': 1–116. Peterborough: Joint Nature Conservation Committee.</ref>
<ref name=Colling>{{cite journal |url=http://floredunordest.free.fr/IMG/pdf/ListeRougeLux.pdf |last1=Colling |first1=G. |date=2005 |title=Red List of the Vascular Plants of Luxembourg |journal=Ferrantia |volume=42 |pages=5–77 }}</ref>
<ref name=Guo>{{cite book |last1=Guo |first1=Y. |last2=Haynes |first2=R.R. |last3=Hellquist |first3=C.B. |last4=Kaplan |first4=Z. |date=2010 |contribution=''Potamogeton'' |title=Flora of China |volume=23 |pages=108–114 |url=http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=222000297 }}</ref>
<ref name=IUCN>{{cite web |url=http://www.iucnredlist.org/details/summary/167905/0 |last1=Allen |first1=D.J. |date=2011 |title=''Potamogeton obtusifolius'' |work=The IUCN Red List of Threatened Species. Version 2014.2 |accessdate=31 October 2014}}</ref>
<ref name=Kap2>[https://www.researchgate.net/publication/259236450_Revision_of_chromosome_numbers_of_Potamogetonaceae_a_new_basis_for_taxonomic_and_evolutionary_implications Kaplan Z., Jarolímová V., Fehrer J, 2013. Revision of chromosome numbers of Potamogetonaceae: a new basis for taxonomic and evolutionary implications. Preslia, 85, 421-482.]</ref>
<ref name=kwc2>[http://www.theplantlist.org/tpl1.1/record/kew-292369 The Plant List: ''Potamogeton obtusifolius''. Royal Botanic Gardens, Kew and Missouri Botanic Gardens. Accessed November 20, 2014]</ref>
<ref name=Moore>[http://fishbull.noaa.gov/33-1/moore.pdf Moore E. 1913. The Potamogetons in relation to pond culture. Bulletin of the U.S. Bureau of Fisheries, 33, 251-291.]</ref> 
<ref name=NewAt>{{cite web |url=http://www.brc.ac.uk/plantatlas/index.php?q=node/2560 |work=Online Atlas of the British and Irish flora |title=''Potamogeton obtusifolius'' }}</ref>
<ref name=Preston>{{cite book |last=Preston |first=C.D. |date=1995 |title=Pondweeds of Great Britain and Ireland. BSBI Handbook No. 8 |publisher=Botanical Society of the British Isles |publication-place=London }}</ref>
<ref name=Sweden>{{cite web |last1=Anderberg |first1=A. |last2=Anderberg |first2=A-L. |url=http://linnaeus.nrm.se/flora/mono/potamogetona/potam/potaobt.html |work=Den Virtuella Floren |title=Trubbnate ''Potamogeton obtusifolius'' }}</ref>
<ref name=USDA>{{cite web |url=http://plants.usda.gov/core/profile?symbol=POOB2 |publisher=United States Department of Agriculture (USDA) Natural Resources Conservation Service |title=Plants Profile for ''Potamogeton obtusifolius'' |accessdate=31 October 2014 }}</ref>
<ref name=Wang>Wang Q.D., Zhang T., Wang J.B. 2007. Phylogenetic relationships and hybrid origin of ''Potamogeton'' species (Potamogetonaceae) distributed in China: insights from the nuclear ribosomal internal transcribed spacer sequence (ITS). Plant Systematics and Evolution, 267, 65-78.</ref>
<ref name=Wiegleb>Wiegleb G., Kaplan Z. 1998. An account of the species of ''Potamogeton'' L. (Potamogetonaceae). Folia Geobotanica, 33, 241-316.</ref>
}}

==External links==
*{{cite web |url=http://linnaeus.nrm.se/flora/mono/potamogetona/potam/potaobtv.jpg |work=Den virtuella floran |title=''Potamogeton obtusifolius'' – Trubbnate Distribution map |language=Swedish}}

{{Taxonbar|from=Q160722}}

[[Category:Potamogeton|obtusifolius]]

{{Sourceattribution|Potamogeton obtusifolius}}