Gnetales
Gnetales | ||||||||||||
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Welwitschia ( Welwitschia mirabilis ) |
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Systematics | ||||||||||||
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Scientific name | ||||||||||||
Gnetales | ||||||||||||
Luerss. |
The Gnetales are an order of the seed plants (Spermatophytina). They are naked animals (gymnosperms) and are currently part of the Coniferopsida due to their molecular genetic characteristics . The order includes 75 species in three genera.
description
In some characteristics the Gnetophyta resemble the Bedecktsamern (Magnoliophyta), but are probably not an ancestor of the same. The Gnetophyta have a woody sprout that runs underground in Welwitschia . The secondary wood contains vessels . The leaves are opposite or whorled.
The flowers are unisexual, so they have either only female or only male organs. They are grouped into inflorescences . The male flowers have a perianth (perianth). The seeds have two cotyledons .
Systematics
Within the Gnetales there are three families , each with only one genus:
- Sea shrub family (Ephedraceae
Dum. )
- Genus Meerträubel ( Ephedra Tourn. Ex L. ): 40 species of shrubs in arid regions of South America, the Sahara, the Mediterranean and Asia.
- Family Gnetaceae Lindl.
- Welwitschiagewächse family (Welwitschiaceae Caruel )
- Genus Welwitschia Hook. f. : There is only one type.
- Welwitschie ( Welwitschia mirabilis Hook. F. ): Namib desert of Namibia and Angola. It forms only two continuously growing, ribbon-shaped leaves and is up to 2000 years old. In 2001, two subspecies were described on the basis of six specimens cultivated in Berlin; this was often cited, but could not be confirmed in field studies. There are still no subspecies.
- Genus Welwitschia Hook. f. : There is only one type.
swell
- Christopher J. Earle: Gnetidae Pax ex Prantl 1894. In: The Gymnosperm Database. March 1, 2019, accessed April 9, 2019 .
- Peter v. Sengbusch: Information from the University of Hamburg.
Individual evidence
- ↑ Nicholas Jacobson, Peter Jacobson, Ernst van Jaarsveld, Kathryn Jacobson: Field evidence from Namibia does not support the designation of Angolan and Namibian subspecies of Welwitschia mirabilis Hook. In: Transactions of the Royal Society of South Africa , Volume 69, Issue 3, 2014, pp. 179-186. doi : 10.1080 / 0035919X.2014.950187 .