Stigonema
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| C. Agardh ex Bornet & Flahault |
Stigonema is a genus of cyanobacteria (blue-green algae).
description
Stigonema forms branched, blue-green to brown threads with a diameter of 7 to 70 µm, single-row in younger parts and several cell layers in older parts. Younger cells are cylindrical, older ones are rounded. Like all bacterial cells, they contain neither cell nuclei nor plastids . The threads lie in a thin jelly. In Stigonema , in contrast to the spuriously branching genera Plectonema , Scytonema and Tolypothrix , there are real branches. They arise when filament cells do not divide perpendicularly, but parallel to the axis . Colorless, thick-walled cells, the so-called heterocysts , which are used for biological nitrogen fixation, are regularly found in the threads . The growth occurs through division of a vertex cell .
Reproduction
The asexual reproduction is done by hormogonia so wenigzelligen, capable of creeping thread fragments.
Sexual reproduction is absent in all cyanobacteria.
Types (selection)
distribution
Stigonema lives on solid substrate in puddles of bog , on rock in mountain streams, but also on damp earth and on wet rocks.
swell
- Karl-Heinz Linne von Berg, Michael Melkonian u. a .: The Kosmos algae guide. The most important freshwater algae under the microscope. Kosmos, Stuttgart 2004, ISBN 3-440-09719-6 .
Web links
- Stigonema at algaebase.org
- Images of Stigonema ocellatum