Rootless dwarf duckweed

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Rootless dwarf duckweed
Rootless dwarf duckweed (Wolffia arrhiza)

Rootless dwarf duckweed ( Wolffia arrhiza )

Systematics
Monocots
Order : Frog-spoon-like (Alismatales)
Family : Arum family (Araceae)
Subfamily : Duckweed family (Lemnoideae)
Genre : Wolffia
Type : Rootless dwarf duckweed
Scientific name
Wolffia arrhiza
( L. ) Horkel ex Wimm.

The rootless dwarf duckweed ( Wolffia arrhiza ), also called rootless dwarf lens or simply dwarf duckweed , is one of about eleven aquatic plant species from the genus of dwarf duckweed ( Wolffia ) that predominantly occur in warm to tropical zones. The genus, like all duckweed , has recently become part of the arum family (previously: Lemnaceae). The generic name is reminiscent of the German botanist Johann Friedrich Wolff (1778–1806).

Duckweed duckweed are the smallest flowering plants in the world.

features

The tiny plant bodies, which are called "shoot members" (not: leaves!) In duckweed, are ellipsoidal to ovoid in Wolffia arrhiza , about 0.5 to 1.5 millimeters long, sometimes slightly translucent and green in color. They drift either individually or in pairs (with a daughter-branch member) on the water surface. In contrast to other duckweed, there are no root threads. It's basically just a few chlorophyll cells that are integrated into a miniature swim pad. A scion member has between ten and one hundred stomata ( stomata ). The plants are monoecious and “bloom” invisibly in secret. There is only one stylus and one stamen - some botanists also interpret this structure as an inflorescence of two unisexual plants. In Central Europe, however, the rootless dwarf duckweed usually remains sterile - the decisive factor here is vegetative reproduction by sprouting and passive spreading with the help of water birds. During the winter, the smaller daughter shoots take on the function of turions , which sink to the bottom of the water in autumn. The remaining members of the shoot then die.

If you rub dwarf duckweed between your fingertips, the consistency feels like granules or like coarse grains of sand. Confusion with stunted specimens of other duckweed should actually be ruled out once you have seen and felt this species (however, please note the information below on possible occurrences of other, neophytic Wolffia species in Europe!).

The number of chromosomes is 2n = 40, 50 or 80.

Occurrence

Miniature duckweed on fingers

The rootless dwarf duckweed needs warmth and grows in the summer half of the year on the surface of moderately nutrient-rich and base-rich, sun-drenched, wind-protected waters, for example in ponds, backwaters , ditches and peat cuttings. It usually appears gregarious, covering the body of water close together with millions of scion limbs. It is usually associated with various other types of pond and duckweed (for example multi-rooted pond lentil , small duckweed ) or with pond liver moss ( Riccia fluitans ). It is considered to be a character species of the Lemnion minoris association and inhabits waters up to a water depth of 150 centimeters.

The species is distributed in Europe from Mediterranean to moderately continental; their distribution area extends from Europe to northern India, also in Asia from South Korea to the Philippines and includes Africa and Australia. In Germany it is considered very rare. Certain major deposits exist in parts of the north German lowlands , including in the Bremen area and near Uelzen . The few known records in southern Germany are probably synanthropic , i.e. they result from human settlements. On the Red List of Germany is Wolffia arrhiza "high risk" as performed.

After finding the very similar Columbian dwarf duckweed ( Wolffia columbiana H. Karst. ) From America in 2013 in Germany and the Netherlands, inspections revealed that several of the alleged occurrences of the rootless dwarf duckweed ( Wolffia arrhiza ) were in reality about this neophyte.

Like Wolffia neglecta , Wolffia arrhiza can also be cultivated as an aquarium plant.

Sources and further information

Size comparison of the smallest ( Wolffia arrhiza ) and the largest ( Spirodela polyrhiza ) duckweed species in Europe

literature

  • Eckhard Garve: Atlas of the endangered fern and flowering plants in Lower Saxony and Bremen. - Nature Conservation Landscape Management Lower Saxony 30 (1994). ISBN 3-922321-68-2 .
  • 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 .
  • Henning Haeupler & Peter Schönfelder : Atlas of the fern and flowering plants of the Federal Republic of Germany . - Ulmer Verlag, Stuttgart, 1988. ISBN 3-8001-3434-9 .
  • Erich Oberdorfer : Plant-sociological excursion flora . - Ulmer Verlag, Stuttgart, 6th edition 1990. ISBN 3-8001-3454-3 .
  • Elfrune Wendelberger: Plants of the wetlands: bodies of water, moors, floodplains. - BLV-Verlag, Munich, 1986. ISBN 3-405-12967-2 .

Web links

Commons : Rootless Duckweed  - Album with pictures, videos and audio files

Individual evidence

  1. ↑ Lotte Burkhardt: Directory of eponymous plant names . Botanic Garden and Botanical Museum Berlin, Free University Berlin Berlin 2016. ISBN 978-3-946292-10-4 . doi : 10.3372 / epolist2016
  2. ↑ a b 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.  120 .
  3. ↑ Rafaël Govaerts (ed.): Wolffia - World Checklist of Selected Plant Families of the Royal Botanic Gardens, Kew. Last accessed on June 18, 2018.
  4. ↑ ULF SCHMITZ, STEFFEN KÖHLER & HASKO NESEMANN: New evidence of the Columbian dwarf duckweed Wolffia columbiana in Europe - How many alleged occurrences of Wolffia arrhiza are actually neophytes? In: Publications of the Bochum Botanical Association 8 (1): 1-10. Bochumer Botanischer Verein, July 9, 2016, accessed on July 16, 2016 .
  5. ↑ Christel Kasselmann : aquarium plants. Ulmer Verlag, Stuttgart 1995; 2nd, revised and expanded edition 1999, ISBN 3-8001-7454-5 , p. 438 f.