Aa (orchids)
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The plant genus Aa belongs to the family of orchids (Orchidaceae). The approximately 26 plant species thrive terrestrially in high altitudes mostly in the Andes .
description
Vegetative characteristics
Aa species grow small, perennial herbaceous plants . The thick and fleshy roots are sometimes hairy. All Aa species form a basal rosette of spirally arranged leaves . The leaves are sometimes thick, fleshy in texture. The leaf blades are oblong-oval to lanceolate with a pointed upper end. The leaves usually only sprout after the flowering period.
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Generative characteristics
The racemose inflorescence appears to the side of the leafy stem axis . The scion bearing the flowers is covered with loose, sheathed, translucent bracts encompassing the stem , but not with foliage leaves. Below it is hairless, but often glandular hairy in the upper area. The small flowers sit close together at the end of the inflorescence axis. They are surrounded by paper-like bracts, which are usually larger than the flowers and which are thrown back when they bloom.
The flowers are not resupinated . The ovary is not stalked, hairless or hairy with glands. The hermaphrodite flowers are zygomorphic and threefold. The bracts are - in contrast to Altensteinia - hardly hairy. The sepals resemble each other, they are free or sometimes fused together at the base for a short distance. The petals are more narrowly shaped. The lip is hemispherical and sits like a hood over the flower, at the base it is provided with two calluses, the edge is fringed and turned inwards. The gynostemium is also hairless and very short. The clinandrium (a tissue at the top of the gynostemium, above the anther ) is greatly reduced. The rostellum (a separating tissue between the anther and the stigma ) is short and lies across the axis of the column. The stigma itself is large, broad, and kidney shaped. The pollen is organized in four soft pollinia , they are linearly shaped.
ecology
The flowers give off an unpleasant odor, which could be related to the attraction of flies as pollinators . Most Aa species seem to reproduce primarily by self-pollination .
Locations
Most Aa species are found in the high altitudes of the Andes in South America and in Costa Rica above the tree line at altitudes of 3000 to 4400 meters. They occur there in the grassy areas called Páramo , in moors, in bamboo thickets, light bushes and Weinmannia forests.
Systematics, botanical history and distribution
The first scientific descriptions of these orchids were provided by Karl Sigismund Kunth , who in 1815 first named a species Ophrys paleacea , and later Altensteinia paleacea . Heinrich Gustav Reichenbach subdivided the genus Altensteinia in 1854 and described the genus Aa with two species, Aa paleacea and Aa argyrolepis . In the first description Xenia Orchidacea. 1. Volume, Brockhaus, Leipzig 1858, page 18 gives Reichenbach no explanation for the unusual name Aa . There is a presumption that he chose the name so that it always appears first in alphabetically sorted lists. But it could also be an honor to Pieter van der Aas , the printer of Paul Hermann's Paradisus Batavus . A third possibility is that the name is derived as an abbreviation from the closely related genus Altensteinia . A few years later Reichenbach reversed his classification and restored all species to Altensteinia , Rudolf Schlechter again created the separation in 1912: in the meantime, significantly more species were known that made a renewed separation appear sensible.
Most Aa species seem to reproduce primarily by self-pollination . The plant specimens therefore look very uniform within individual populations , although significant deviations can occur with neighboring populations of the same species. Since the descriptions of the Aa species are based only on very limited collections that do not cover the entire range of variation, the taxonomic status and the delimitation of the species is uncertain.
Most Aa species are found in the high altitudes of the Andes in South America and in Costa Rica .
There are about 26 types of Aa :
- Aa achalensis Schltr. , North-central Argentina (La Rioja, San Luis , Córdoba )
- Aa argyrolepis (Rchb. F.) Rchb. f. , Colombia , Ecuador , Peru and northern Brazil
- Aa aurantiaca D. Trujillo , Peru
- Aa calceata (Rchb. F.) Schltr. , Peru to Bolivia
- Aa colombiana Schltr. , Colombia to Ecuador
- Aa denticulata Schltr. , Colombia to Ecuador
- Aa erosa (Rchb. F.) Schltr. , Peru
- Aa fiebrigii (Schltr.) Schltr. : It occurs from Bolivia to northwest Argentina.
- Aa figueroi Szlach. & S.Nowak , Colombia
- Aa hieronymi (Cogn.) Schltr. , Northwest Argentina to Cordoba
- Aa lehmannii Rchb. f. ex Szlach. & Kolan. , Ecuador
- Aa leucantha (Rchb. F.) Schltr. , Colombia to Ecuador
- Aa lorentzii Schltr. : It occurs in northwestern Argentina.
- Aa lozanoi Szlach. & S.Nowak , Colombia
- Aa macra Schltr. , Colombia and Ecuador
- Aa maderoi Schltr. (Syn .: Aa hartwegii Garay ), northwestern Venezuela to Ecuador and Colombia
- Aa mandonii (Rchb. F.) Schltr. , Peru to Bolivia
- Aa matthewsii (Rchb. F.) Schltr. : It occurs in Peru to western Bolivia.
- Aa microtidis Schltr. : It occurs in Bolivia.
- Aa nervosa (Kraenzl.) Schltr. , northern Chile
- Aa paleacea (Kunth) Rchb. f. , Costa Rica to Bolivia
- Aa riobambae Schltr. , Ecuador
- Aa rosei Ames , Peru
- Aa schickendanzii Schltr. : It occurs in northwestern Argentina.
- Aa sphaeroglossa Schltr. : It occurs in Bolivia.
- Aa trilobulata Schltr. : It occurs in Bolivia.
- Aa weddeliana (Rchb. F.) Schltr. : It occurs from Peru to northwest Argentina.
See also
Individual evidence
- ↑ WE Higgins: Selby Vignette, The Aa's of Orchids. (No longer available online.) 2006, archived from the original on November 29, 2010 ; Retrieved August 24, 2009 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ HG Reichenbach: Xenia Orchidacea. 1. Volume, Brockhaus, Leipzig 1858, p. 18. scanned at botanicus.org .
- ^ RE Schultes, AS Pease: Generic Names of Orchids. Their Origin and Meaning. New York, Academic Press 1963. cit. n. Barringer, 1984.
- ↑ European Orchid Congress - Paradisus Batavius ( Memento of March 13, 2007 in the Internet Archive )
- ↑ Lotte Burkhardt: Directory of eponymous plant names - Extended Edition. Part I and II. Botanic Garden and Botanical Museum Berlin , Freie Universität Berlin , Berlin 2018, ISBN 978-3-946292-26-5 doi: 10.3372 / epolist2018 .
- ^ CH Dodson, CA Luer: Orchidaceae part 2 (Aa-Cyrtidiorchis) . In: G. Harling, L. Andersson (Eds.): Flora of Ecuador . tape 76 . Botanical Institute Göteborg University, Göteborg 2005, ISBN 91-88896-51-X , p. 6 .
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab Rafaël Govaerts (Ed.): Aa. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved April 3, 2020.
literature
- K. Barringer: Aa (Orchidaceae) in Costa Rica . In: Phytologia . tape 55 , no. 6 , 1984, ISSN 0031-9430 , pp. 443-446 .
- Leslie A. Garay: Orchidaceae (Cypripedioideae, Orchidoideae and Neottioideae) . In: Gunnar Harling, Benkt Sparre (ed.): Flora of Ecuador . Vol. 225, Vol. 9, No. 1 , 1978, ISSN 0347-8742 , p. 298 .
- Alec M. Pridgeon, Phillip Cribb, Mark W. Chase, Finn Rasmussen (Eds.): Genera Orchidacearum. Orchidoideae . Part 2. Vanilloideae. tape 3/2 . Oxford University Press, New York / Oxford 2003, ISBN 0-19-850711-9 , pp. 24-26 .
- Rudolf Schlechter: Repertorium specierum novarum regni vegetabilis . tape 32 . Berlin 1912, p. 147 ff . ( botanicus.org ).
