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''Potamogeton acutifolius'' is a European species of aquatic plant in the family Potamogetonaceae, known by the common name sharp-leaved pondweed. It is threatened and declining in at least part of its range. ==Description== Sharp-leaved pondweed grows annually from turions and seed, producing rather lax plants branching near the surface with strongly compressed stems and long, rather grass-like leaves that are 35–100 mm long and 1.5–5 mm wide and dark green, often with a marked reddish or brownish tinge.〔 Each leaf has one vein either side of the midrib. There are no rhizomes or floating leaves. The inflorescences are up to 6 mm long with 4-6 flowers with a short peduncle (5–20 mm long, occasionally more).〔 Within its range, sharp-leaved pondweed is relatively easily identified from all other pondweeds except the closely related grass-wrack pondweed (''P. compressus'') by its combination of strongly flattened stems, sclerenchymatous strands in the leaf (giving the submerged leaves an opaque appearance compared with the transparent appearance of other pondweeds) and leaves with sharply pointed (acute) tips.〔 Grass-wrack pondweed differs in having blunter tips to the leaves, leaves with 2 veins either side of the midrib, and infloresecences with 10-20 flowers on long peduncles, 28–95 mm long.〔 Hybrids with ''P. berchtoldii'' (''P.'' × ''sudermanicus'' Hagstr.) and ''P. friesii'' (''P.'' × ''pseudofriesii'' Dandy & G.Taylor) have been recorded. Both are rare.〔 In northeast Europe, DNA evidence indicates that hybrids with ''P. compressus'' are fairly frequent, but often overlooked because of the difficulty of reliably identifying them.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Potamogeton acutifolius」の詳細全文を読む スポンサード リンク
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