Plectonemaex Gomont, 1892
Lectotype species: Plectonema tomasinianum Bornet ex Gomont
Original publication and holotype designation: Gomont, M. (1892 '1893'). Monographie des Oscillariées (Nostocacées Homocystées). Deuxième partie. - Lyngbyées. Annales des Sciences Naturelles, Botanique, Série 7 16: 91-264, pls 1-7.
Taxonomic status: currently recognized as a distinct genus.
Most recent taxonomic treatment adopted: Komárek, J., Kastovsky, J., Mares, J. & Johansen, J.R. (2014). Taxonomic classification of cyanoprokaryotes (cyanobacterial genera) 2014, using a polyphasic approach. Preslia 86: 295-335.
Description: Filamentous; filaments long, isopolar, solitary or in macroscopic clusters, usually waved or coiled, always with more or less thick, firm, colorless sheaths, sometimes slightly lamellated, open at the apex, obligately and frequently false-branched. Trichomes isopolar, 8-25 _m wide, uniseriate, composed of short cylindrical or barrel-like (discoid) cells (always shorter than wide, usually several times), constricted or unconstricted at the crosswalls, not attenuated or very shortly attenuated towards the ends, nonmotile (with exception of hormogonia). Cells without aerotopes, sometimes with granular, blue-green, olive-green or grey-blue content; end cells widely rounded, sometimes capitate or with slightly thickened outer cell wall. Heterocytes and akinetes absent. Cell division crosswise, perpendicular to the long axis of a trichome, in a rapid sequence. Irregular meristematic zones. Reproduction by motile hormogonia, escaping from sheaths at the ends of filaments, by means of necridic cells. Hormogonia germinate and grow at both ends (isopolar development). The absence of heterocytes was doubted by Hoffmann and Demoulin (1985); in the case of heterocyte production Plectonema must be transferred to Scytonema (Nostocales). In clear (usually katharobic to oligosaprobic) water basins, springs or creeks, in metaphyton and periphyton.
Information contributed by: J. Komárek. The most recent alteration to this page was made on 14 Apr 2015 by Wendy Guiry.
Numbers of names and species: There are 66 species names in the database at present, as well as 15 infraspecific names. Of the species names, 18 have been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..
Names: ('C' indicates a name that is accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):
Click here to also show infraspecific names in the list below.
Verification of data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.
Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.
Created: 11 April 2002 by M.D. Guiry
Verified by: 14 April 2015 by Wendy Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=43619
Please cite this record as:
Wendy Guiry in Guiry, M.D. & Guiry, G.M. 2019. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 23 April 2019.