Water salad

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Water salad
Pistia stratiotes in the garden pond

Pistia stratiotes in the garden pond

Systematics
Monocots
Order : Frog-spoon-like (Alismatales)
Family : Arum family (Araceae)
Tribe : Pistieae
Genre : Pistia
Type : Water salad
Scientific name of the  tribe
Pistieae
Rich.
Scientific name of the  genus
Pistia
L.
Scientific name of the  species
Pistia stratiotes
L.

The water lettuce ( Pistia stratiotes ), also Green Water Rose or Muschelblume called, is the only species of the genus Pistia within the family of the arum family (Araceae). This floating plant can be found in freshwater in tropical and subtropical zones around the world . It is used as an ornamental plant both in ponds and, above all, in aquaristics .

description

The water lettuce is an aquatic, stemless, perennial herbaceous plant . It forms a multitude of long roots . The alternate and spirally arranged leaves in a rosette are sessile. The pale green, spongy leaf blade , densely covered with fine trichomes consisting of a few cells, is 4 to 5 cm wide and obovate with a broadly rounded upper end and a bulged edge.

Inflorescences of the water salad

The inflorescence stands on a short stem in the axilla of an inner rosette leaf. Each inflorescence is of a whitish bract (= spathe ). which is hairless on the inside and tomentose on the outside. The spathe is constricted in the middle. Below the constriction sits a single, strongly reduced female flower, in the upper area mostly 5–8 male flowers arranged in a ring. The female flowers have a single, single-chamber, ovoid ovary with a plurality of closely spaced ovules , the orthotroph (perpendicular) are arranged in rows 4 to 6. The stylus is short and has a spherical scar . The male flowers each consist of two stamens that are slightly fused with each other, the anthers open with two vertical slits.

The small, egg-shaped berry contains few to many seeds. The fruit pops up irregularly, releasing the seeds. The seeds are cylindrical in shape, slightly cut off at the top and hollowed out in the middle.

The number of chromosomes is 2n = 28.

ecology

The wettability of the leaf surface is poor due to the strong hair and water that hits it rolls off. However, this is not the lotus effect , but rather the Salvinia effect .

Occurrence

The water lettuce occurs in the tropics and subtropics of the Old and New World, in America its distribution area extends in the north to southern Texas and Florida . It is a very old, genetically isolated line of development.

The water salad is mostly found in stagnant fresh water, mostly on the edge of lakes and ponds. Mostly you can find it at altitudes of up to 1200 meters, occasionally it can also be found in higher altitudes.

The water lettuce has been spreading as a neophyte in the Erft in North Rhine-Westphalia since 2008 . Through marsh water , which is channeled into the Erft to drain the nearby lignite mine, the water temperature does not fall below 10 ° C in winter, which means that the water salad does not freeze back even in frosty conditions.

Aquaristics

In the aquarium hobby, the water lettuce is called either by its scientific name or by the German name Muschelblume . It is a popular floating plant that can adapt to various water parameters and is easy to cultivate given its ability to reproduce. As a fast-growing plant, it also helps to counteract the formation of algae in the aquarium in a natural way .

Problems with the care of this plant are mostly reported with regard to the development of rot on the leaves. According to Kasselmann, however, this phenomenon is not due to the formation of condensation between the water surface and the aquarium cover.

Individual evidence

  1. ↑ Christel Kasselmann : Aquarium plants - 450 species in portrait. 3. Edition. Ulmer, Stuttgart 2010, p. 480.
  2. ↑ Close-up of inflorescence
  3. ^ A b Paul C. Standley, Julian A. Steyermark: Flora of Guatemala. (= Fieldiana Botany. Volume 24, Part I). Chicago Natural History Museum, 1958, pp. 347-348. (archive.org)
  4. ^ Tropicos. (tropicos.org)
  5. ↑ Armin Jagel, Annette Höggemeier: Pistia stratiotes - water salad (Araceae). Bochum Botanical Association, 2015 (botanik-bochum.de , PDF, 1.1 MB)
  6. ↑ SS Renner, LB Zhang: Biogeography of the Pistia clade (Araceae): Based on chloroplast and mitochondrial DNA sequences and Bayesian divergence time inference. In: Systematic biology. Volume 53, No. 3, pp. 422-432. doi: 10.1080 / 10635150490445904 . Biogeography of the Pistia Clade (Araceae)
  7. ↑ Andreas Hussner, Sabine Heiligtag: Pistia stratiotes L. (Araceae), the mussel flower, in the area of ​​the lower Erft (North Rhine-Westphalia): Spreading tendency and problem potential. In: Yearbook of the Bochum Botanical Association. Volume 5, 2014, pp. 58-63 (PDF file) .
  8. ↑ Christel Kasselmann: aquarium plants. 2nd, revised and expanded edition. 1999, ISBN 3-8001-7454-5 , p. 399.

Web links

Commons : Water Salad  - Album with pictures, videos and audio files