Bluntleaf Pondweed (Potamogeton obtusifolius)
Description
Blunt-leaved pondweed grows annually from 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) mm long and 1.5-3.55 mm wide and pale green, often with a very marked reddish or brownish tinge 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,though close inspection usually reveals a narrow point at the tip. The stipules 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 mm long with 6-8 flowers in each. Fruits, which are approximately 3 - 2 mm, are freely produced.Blunt-leaved pondweed could be confused with other fine-leaved pondweeds within its range, especially Potamogeton berchtoldii and P. friesii,but potentially also 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.
Taxonomic tree
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Domain: Eukarya
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Kingdom: Plantae
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Phylum: Magnoliophyta
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Class: Liliopsida
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Order: Alismatales
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Family: Potamogetonaceae
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Genus: Potamogeton
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