Arthrocnemum
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Arthrocnemum is a genus of plants in the foxtail family(Amaranthaceae). They are shrubby salt plants with fleshy, apparently articulatedstemsand greatly reduced leaves and flowers. There are only about two species distributed from Macaronesia and western tropical Africa across the Mediterranean to Southwest Asia.
description
Vegetative characteristics
The Arthrocnemum species are small shrubs that can reach heights of up to 1.5 meters. They are strongly branched from the base and often form dense mat-like stands. The bark of this year's twigs is blue-green (sometimes yellowish) and bare.
The opposite leaves are fleshy, fused at the base and cup-like surrounding the stem, reduced to small scales with a length of up to 5 millimeters and drawn out into a fine point at the top. Between the leaf scales, gaps can be seen on the stems.
Inflorescences and flowers
The inflorescences standing at the end of the side branches are spike-like unbranched or can contain short paracladia . They consist of opposite, three-flowered cymes , each of which arises from the axilla of a bract.
The flowers are hermaphroditic (sometimes the stamens are missing on the side flowers) and protandric . The central flower is square, the side ones are triangular. The three to four tepals are usually fused to the tip, stand upright and protrude beyond the bracts by a third or half of the length. They consist of several layers of thin-walled cells with scattered woody cells, but never harden completely. The flowers contain one or two protruding stamens 0.8 to 1.3 millimeters in length. The ovary is conical. The stylus ends in two scars .
Fruits and seeds
The pericarp consists of thick and multi-layered parenchyma in the upper part and thin parenchyma in the lower part . The seeds are reddish when immature and later turn black. The crust-like seed coat usually has papilla-like, conical outgrowths on one side. The embryo is vertical and bent like a comma, there is a nutrient tissue.
Occurrence
The distribution area of Arthrocnemum includes (after excluding the American species, see below) the Mediterranean area , Macaronesia , western tropical Africa , the northern Sahara and Southwest Asia (Saharo-Arab region).
As typical salt plants (halophytes), the species colonize salt marshes on the sea coasts and salty locations inland.
Systematics
The genus Arthrocnemum was 1840 Alfred Moquin-Tandon installed . A type species has not yet been validly defined.
In the genus Arthrocnemum numerous species were previously combined, which are placed in other genera within the tribe Salicornieae (for example, to Sarcocornia and Tecticornia ). Arthrocnemum is clearly delineated both in terms of molecular genetics and in terms of its fruit characteristics .
Arthrocnemum is closely related to the monotypic genus Microcnemum .
According to Sukhorukov & Nilova 2016, the genus Arthrocnemum only contains two species:
- Arthrocnemum franzii Sukhor. : It occurs in western tropical Africa ( Cape Verde ) on the islands of Sal , Maio and Boa Vista .
- Arthrocnemum macrostachyum (Moric.) C. Koch : It iswidespreadin the Mediterranean region , Macaronesia , the northern Sahara and southwest Asia .
Type to be excluded:
- Arthrocnemum subterminale (Parish) Standl. : It occurs from California to Mexico . This species has different characteristics and should be excluded from the genus according to Sukhorukov & Nilova 2016.
literature
- Alexander P. Sukhorukov, Maya V. Nilova: A new species of Arthrocnemum (Salicornioideae: Chenopodiaceae-Amaranthaceae) from West Africa, with a revised characterization of the genus. In: Botany Letters 2016. doi : 10.1080 / 23818107.2016.1185033 .
Individual evidence
- ^ Alfred Moquin-Tandon: Chenopodearum Monographica Enumeratio. Paris, 1840, pp. 111-113. First description scanned at BHL.
- ↑ Gudrun Kadereit, Ladislav Mucina, Helmut Freitag: Phylogeny of Salicornioideae (Chenopodiaceae): diversification, biogeography, and evolutionary trends in leaf and flower morphology. In: Taxon , Volume 55, Issue 3, 2006, pp. 617-642.
- ^ Peter W. Ball: Arthrocnemum . In: Flora of North America Editorial Committee (Ed.): Flora of North America North of Mexico . Volume 4: Magnoliophyta: Caryophyllidae, part 1 . Oxford University Press, New York / Oxford a. a. 2003, ISBN 0-19-517389-9 , pp. 381 (English).
Web links
Wikispecies: Arthrocnemum - Species Directory- Arthrocnemum at Tropicos.org. Missouri Botanical Garden, St. Louis, accessed September 15, 2017.
- Arthrocnemum at Tropicos.org. In: IPCN Chromosome Reports . Missouri Botanical Garden, St. Louis
- Arthrocnemum at Tropicos.org. In: Flora of Pakistan . Missouri Botanical Garden, St. Louis
- Arthrocnemum at Tropicos.org. In: Flora Palestine . Missouri Botanical Garden, St. Louis
- Mikko Piirainen 2009: Arthrocnemum. In: P. Uotila, (Ed.): Chenopodiaceae. In: Euro + Med Plantbase - the information resource for Euro-Mediterranean plant diversity.