Horn leaf


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Horn leaf
Rough horn leaf (Ceratophyllum demersum), illustration

Rough horn leaf ( Ceratophyllum demersum ), illustration

Systematics
Department : Vascular plants (tracheophyta)
Subdivision : Seed plants (Spermatophytina)
Class : Bedecktsamer (Magnoliopsida)
Order : Horn leaf-like
Family : Horn leaf family
Genre : Horn leaf
Scientific name of the  order
Ceratophyllales
link
Scientific name of the  family
Ceratophyllaceae
Gray
Scientific name of the  genus
Ceratophyllum
L.

Horn leaf ( Ceratophyllum ), sometimes misleadingly referred to as hornwort (this is already the German name of the genus Cerastium ), forms the only genus of the horn leaf family (Ceratophyllaceae) and the horn leaf-like order (Ceratophyllales) within the flowering plants (Magnoliopsida). The genus name Ceratophyllum is derived from the Greek words keras for horn and phyllon for leaf. These aquatic plants are not to be confused with the candelabrum algae, which sometimes look very similar .

description

Ceratophyllum species consist of a central stem axis with a tensile, but fragile stem to which leaves and lateral axes are attached. The main axis reaches a length of about 1 meter. Ceratophyllum species do not have roots to anchor in the ground. They float freely in the water and absorb nutrients through root-like structures that have arisen from transformed sprouts. The plant continues to grow on one end while it dies on the other end.

The leaves are made up of whorls (whorls) and bifurcate one to several times depending on the species. In the frequently occurring rough horn leaf, for example, they are once or twice forked, dark green and end in two to four rigid, rough, linear tips. In the rarer Zarten Hornblatt they are lighter green, finer and three to four times forked with five to eight tips. The horn leaf usually only blooms in warm summers. From June to September, small inconspicuous greenish flowers form in the leaf axils.

Male flowers of the rough horn leaf ( Ceratophyllum demersum )

The horn leaf species are single sexed ( monoecious ). The very inconspicuous flowers are in the leaf axils, but can hardly be observed. Also, fertilization and seed formation take place under water.

As a rule, however , the plant spreads vegetatively , with the brittle shoot axes disintegrating in spring. A new individual grows out of every fragment. In addition, starch-rich winter buds ( turions ) are formed in autumn , which detach and sink to the bottom. New plants also emerge from them in spring.

Occurrence

The genus Ceratophyllum is represented worldwide with around ten species in freshwater. Ceratophyllum species grow in stagnant or slow-flowing, summer-warm, nutrient-rich, often even hypertrophic (polluted) waters.

Systematics

The species in this family are very different from all other flowering plants. They are probably the sister group of the eudicotyledons , but possibly also the monocotyledons or the Chloranthaceae .

The genus Ceratophyllum was set up in 1753 by Carl von Linné in Species Plantarum .

Rough horn leaf ( Ceratophyllum demersum )
Tender horn leaf ( Ceratophyllum submersum )

There are about five (to ten) species in the genus Ceratophyllum :

  • Raues horn leaf ( Ceratophyllum demersum L. ): It is distributed worldwide, several varieties belong to it.
  • Ceratophyllum echinatum A.Gray : It is found from western Canada to the northwestern United States and from central and eastern Canada to the central and eastern United States.
  • Ceratophyllum muricatum Cham. : It is distributed almost worldwide with three subspecies.
    • Ceratophyllum muricatum subsp. australe (Griseb.) Les : It occurs in the southeastern United States, in Cuba and from central and southern Mexico to tropical South America and Trinidad. It is also viewed by some authors as a separate species: Ceratophyllum australe Griseb.
    • Ceratophyllum muricatum subsp. kossinskyi (Kuzen.) Les : It occurs from Southeast Europe to China.
    • Ceratophyllum muricatum subsp. muricatum : It occurs in Africa, Asia and on islands in the southwestern Pacific.
  • Broad spiny horn leaf ( Ceratophyllum platyacanthum Cham. ): It comprises two subspecies. The species is native to the temperate zones of Eurasia. However, some authors consider both subspecies to be varieties of Ceratophyllum demersum .
    • Ceratophyllum platyacanthum subsp. oryzetorum (Kom.) Les (Syn .: Ceratophyllum demersum var. quadrispinum Makino ): It occurs from Siberia to temperate East Asia.
    • Ceratophyllum platyacanthum subsp. platyacanthum (Syn .: Ceratophyllum demersum var. platyacanthum (Cham.) Wimm. ): It occurs in Central and Northeastern Europe.
  • Tender horn leaf ( Ceratophyllum submersum L. ): It is distributed in two varieties from Europe to Central Asia, from tropical Africa to the Arabian Peninsula, in the southeastern United States and on Hispaniola.
  • Ceratophyllum tanaiticum Sapegin : It occurs in eastern Central Europe and in Eastern Europe.

Aquaristics

Various types of horn leaf are used in the aquarium hobby. They are characterized by strong growth and help to improve the water quality. Their ability to absorb nutrients dissolved in the water also makes them suitable for combating algae.

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Individual evidence

  1. Angiosperm Phylogeny Group : An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. In: Botanical Journal of the Linnean Society. Volume 161, No. 2, 2009, pp. 105-121, doi: 10.1111 / j.1095-8339.2009.00996.x .
  2. Carl von Linné: Species Plantarum. Volume 2, Lars Salvius, Stockholm 1753, p. 992, digitizedhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fwww.biodiversitylibrary.org%2Fopenurl%3Fpid%3Dtitle%3A669%26volume%3D2%26issue%3D%26spage%3D992%26date%3D1753~GB%3D~ IA% 3D ~ MDZ% 3D% 0A ~ SZ% 3D ~ double-sided% 3D ~ LT% 3D ~ PUR% 3D
  3. a b c d e f g h i j k l m n Rafaël Govaerts (Ed.): Ceratophyllum. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved September 25, 2019.
  4. a b c Walter Erhardt , Erich Götz, Nils Bödeker, Siegmund Seybold: The great pikeperch. Encyclopedia of Plant Names. Volume 2. Types and varieties. Eugen Ulmer, Stuttgart (Hohenheim) 2008, ISBN 978-3-8001-5406-7 .
  5. ^ A b Donald H. Les: Ceratophyllaceae. In: Flora of North America Editorial Committee (Ed.): Flora of North America North of Mexico . Volume 3: Magnoliophyta: Magnoliidae and Hamamelidae . Oxford University Press, New York / Oxford a. a. 1997, ISBN 0-19-511246-6 , Ceratophyllum , p. 81-84 (English).

Web links

Commons : Hornblatt  - collection of images, videos and audio files