Thorny pondweed

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Thorny pondweed
Spiny pondweed (Potamogeton friesii)

Spiny pondweed ( Potamogeton friesii )

Systematics
Class : Bedecktsamer (Magnoliopsida)
Monocots
Order : Frog-spoon-like (Alismatales)
Family : Pondweed family (Potamogetonaceae)
Genre : Spawn herbs ( Potamogeton )
Type : Thorny pondweed
Scientific name
Potamogeton friesii
Rupr.

The spiny pondweed ( Potamogeton friesii , syn .: Potamogeton mucronatus ) is a submerged ( submerged ) representative of the family of the pondweed family (Potamogetonaceae). Narrow-leaved forms are easy to confuse with the common dwarf pondweed ( Potamogeton pusillus ).

The scientific name honors the Swedish botanist and mycologist Elias Magnus Fries (1794–1878).

Occurrence

The spiny pondweed occurs circumpolarly in the submeridional to boreal climatic zone from the flat to the hill country. It is widespread in the temperate latitudes of the northern hemisphere and grows preferentially in meso- to eutrophic lakes. It is also less common in slow-flowing waters. The locations are mostly on humus or peaty mud soils. Some shade is tolerated. The species is a characteristic of the plant association Hottonietum palustris and has its main occurrence in the association Potamogetonion pectinati.

Its populations are threatened throughout Germany due to water pollution and increasing eutrophication of the water. In Saxony-Anhalt, Saxony, Hesse and Rhineland-Palatinate, it is already considered lost. In the other federal states it is on the red list of vascular plants.

Important identification feature: leaf tip and outgoing leaf veins
Another important characteristic: outgoing leaf median nerves in the upper half of the leaf center

Identifying features

The spiny pondweed can reach a length of almost 1.5 m. It forms a relatively thick main shoot , from which many significantly shorter side branches branch off, which appear compressed in cross section and are blunt-edged. However , the spiny pondweed usually does not form a rhizome . All leaves are submerged, up to 10 cm long and about 1.5 to 4 mm wide. They are greenish in color and turn brown as they age. The leaves appear rounded at the front and have a characteristic short, attached tip. The leaves have 5 nerves (rarely 3 or 7), with the middle nerve being provided with air tissue. An important determinant is the way in which the leaf veins originate from the midrib. Just below the tip of the leaf, two nerves emerge, slightly offset. In the upper half of the middle of the leaf this time 2 leaf veins come off slightly offset from one side only; on the other side, a little further up, another one. The stipules are often two-columned to the base.

The spiny pondweed flowers from June to August, the individual flowers are not very close together in an approximately 0.8 to 1.5 cm long spike . The ear stalk, which is thickened towards the top, is about 1.5 to 3 cm, rarely up to 6 cm long. The fruits measure about 1.5 cm in diameter, they are often longer than wide and bumpy. In autumn, spindle-shaped winter buds ( turions ) are also formed, which are terminal or axillary.

The number of chromosomes is 2n = 26.

literature

  • Henning Haeupler , Thomas Muer: picture atlas of the fern and flowering plants of Germany (= the fern and flowering plants of Germany. Volume 2). Published by the Federal Agency for Nature Conservation. Ulmer, Stuttgart 2000, ISBN 3-8001-3364-4 , p. 576.
  • Erich Oberdorfer: Plant-sociological excursion flora . 7th edition. Ulmer, Stuttgart 1994, ISBN 3-8252-1828-7 , pp. 103 .
  • Potamogeton friesii. In: FloraWeb.de.

Individual evidence

  1. ↑ Rafaël Govaerts (ed.): Potamogeton friesii. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Accessed June 1, 2020.
  2. ^ Erich Oberdorfer : Plant-sociological excursion flora for Germany and neighboring areas . With the collaboration of Angelika Schwabe and Theo Müller. 8th, heavily revised and expanded edition. Eugen Ulmer, Stuttgart (Hohenheim) 2001, ISBN 3-8001-3131-5 , pp.  103-104 .

Web links

Commons : Thorny pondweed ( Potamogeton friesii )  - Collection of images, videos and audio files