Potamogeton praelongus
| Potamogeton praelongus | |
|---|---|
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| Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Order: | Alismatales |
| Family: | Potamogetonaceae |
| Genus: | Potamogeton |
| Species: | P. praelongus |
| Binomial name | |
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Potamogeton praelongus Wulfen |
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| Synonyms | |
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Potamogeton acuminatus Wahlenb. Potamogeton flexuosus Wredow Potamogeton flexuosus Schleich. Spirillus praelongus (Wulfen.) Nieuwl. |
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Potamogeton acuminatus Wahlenb. Potamogeton flexuosus Wredow Potamogeton flexuosus Schleich. Spirillus praelongus (Wulfen.) Nieuwl.
Potamogeton praelongus, commonly known as whitestem pondweed in North America and Long-stalked Pondweed in Britain, is a large, perennial aquatic plant in the family Potamogetonaceae. It is widely distributed in lakes and rivers in the northern hemisphere, but is sensitive to poor water quality.
Long-stalked pondweed has tall stems to 3 m growing from stout, rusty-spotted perennial rhizomes. The stems often change direction between each node, giving a characteristic zig-zagging pattern. The transparent pale to deep green leaves are typically between 60 and 150 mm long but occasionally reach 250 mm and are 14–40 mm wide. The stipules are persistent, open, whitish and translucent, with prominent veins when dry. Floating leaves and turions are absent. The inflorescences are produced quite early for a pondweed, in May–June, and have 15-20 inconspicuous greenish flowers and held on robust peduncles 80–200 mm long. The fruits are large for a pondweed, 4.5-5.5 x 2.5-3.6 mm.
Hybrids with several other species, P. alpinus (P. × griffithii A. Benn.), P. crispus (P. × undulatus Wolgf.), P. lucens (P. × jutlandicus Zalewska-Gał.), P. natans (P. × vepsicus A.A. Bobrov & Chemeris) and P. perfoliatus (P. × cognatus Asch. & Graebn.) have been described, but all are rare.Chromosome counts show that, like most other broad-leaved pondweeds, P. praelongus is tetraploid, with 2n=52 chromosomes.
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