Yellow-green algae

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Yellow-green algae
Alger, Botydium granulatum, Nordisk familjebok.png
Botydium granulatum
Scientific classification
Domain: Eukaryota
Kingdom: Chromalveolata
Phylum: Heterokontophyta
Class: Xanthophyceae
Allorge ex Fritsch
Synonyms

Yellow-green algae or xanthophytes are an important group of heterokont algae. Most live in freshwater, but some are found in marine and soil habitats. They vary from single-celled flagellates to simple colonial and filamentous forms. Xanthophyte chloroplasts contain the photosynthetic pigments Chlorophyll a, Chlorophyll c, β-Carotene, and the carotenoid diadinoxanthin.[1] Unlike other heterokonts, their chloroplasts do not contain fucoxanthin, which accounts for their lighter colour. Its storage polysaccharide is chrysolaminarin.[1] Xanthophyte cell walls are produced of cellulose and hemicellulose.[1] They appear to be the closest relatives of the brown algae.

Classifications[edit]

The Xanthophyceae have been divided into the following four orders in some classification systems:

Recent ultrastructural and molecular phylogenetic DNA (nuclear and plastid) research shows that the Mischococcales might be paraphyletic, and the Tribonematales and Botrydiales polyphyletic, and suggests two orders at most be used until the relationships within the division are sorted.[3]

The Xanthophyceae were placed before in the division Chrysophyta, e.g., in the classification of Smith (1938). In this classification, there are six orders:

In a classification presented by Hoek, Mann and Jahns (1995), based on the level of organization of the thallus, there are seven orders:

Informal groups, according to Maistro et al. (2009):[4]

  • Botrydiopsalean clade
  • Chlorellidialean clade
  • Tribonematalean clade
  • Vaucherialean clade

Unicellular flagellates, amoeboid and palmelloid taxa were not included in this study.

According to Adl et al. (2012):[5]

  • Tribonematales (genera Botrydium, Bumilleriopsis, Characiopsis, Chloromeson, Heterococcus, Ophiocytium, Sphaerosorus, Tribonema, Xanthonema)
  • Vaucheriales (genus Vaucheria)

See also[edit]

References[edit]

  1. ^ a b c Stace, Clive A. Plant Taxonomy and Biosystematics. Cambridge University Press, 1991. ISBN 978-0-521-42785-2. 
  2. ^ Christensen, T. 1987. Seaweeds of the British Isles. Volume 4 Tribophyceae (Xanthophyceae). British Museum (Natural History), London ISBN 0-565-00980-X
  3. ^ Adl SM, Simpson AG, Farmer MA, et al. (2005). "The new higher level classification of eukaryotes with emphasis on the taxonomy of protists". J. Eukaryot. Microbiol. 52 (5): 399–451. doi:10.1111/j.1550-7408.2005.00053.x. PMID 16248873. 
  4. ^ http://www.sciencedirect.com/science/article/pii/S1434461009000091
  5. ^ http://www.ncbi.nlm.nih.gov/pubmed/23020233