Trebouxia
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| Puymaly , 1924 |
Trebouxia is a seaweed genus from the class of Trebouxiophyceae . It is the most common algae partner in lichens - symbioses and occurs in more than half of all known species of lichens.
description
Trebouxia species are unicellulars . The cell diameters are 10 to 15 (-20) μm. Adult vegetative cells have a large central, lobed or star-shaped chloroplast with a pyrenoid in the center. The cytoplasm is limited to a narrow border between the chloroplast and the plasmalemma . The cell nucleus lies in an indentation of the chloroplast.
Occurrence and Physiology
The representatives of the genus Trebouxia live on soil surfaces or epiphytic and represent the most common green algae species, a lichen - symbiosis remembered as the photobiont. They occur in more than half of all known types of lichen and have a high tolerance to dehydration. In the wild, however, at least some species have also been observed and are then about twice the size than in the symbiosis.
Lichenized (i.e. living in a lichen symbiosis) Trebouxia mainly produces sugar alcohols (80% ribitol ), while in free- living cells sugar alcohols take a back seat to other carbohydrates . Trebouxia is also able to live saprophytically in the absence of light .
Multiplication
In the lichen symbiosis, autospores are formed for asexual reproduction , and under humid conditions and in culture also mobile stages ( zoospores ). Sexual reproduction has also been observed; it occurs isogamously or anisogamously by fusing biflagellate (biflagellated) gametes.
Systematics
Algaebase lists 36 species within the genus Trebouxia , 28 of which are taxonomically accepted. The holotype is Trebouxia arboricola .
Individual evidence
- ^ Protist Information Server
- ↑ Trebouxia MD Guiry in MD Guiry and GM Guiry, 2017. AlgaeBase. National University of Ireland, Galway. http://www.algaebase.org; last accessed on November 25, 2017
literature
- Georg Masuch: biology of lichens . Quelle & Meyer, Heidelberg / Wiesbaden (UTB f. Wissenschaft), 1993, ISBN 3-8252-1546-6 , pp. 79-80.
- Robert Edward Lee: Phycology . Cambridge University Press, 4th ed. 2008, ISBN 978-0-521-68277-0 , p. 217