Anabaena sp. (Bory) ex Bornet & Flah., 1888
The trichomes are unbranched, straight or coiled. The gelatinous sheaths surrounding the trichomes are generally watery such that they are not apparent unless demonstrated by special methods. The cells are spherical to barrel-shaped with constrictions at the cross-walls. There are numerous heterocysts that are ellipsoidal and larger than the vegetative cells. Akinetes are larger still, cylindrical and with rounded ends.
This is a cosmopolitan genus that occurs primarily in freshwater.
Mainly freshwater, although a few species occur in the marine environment. Anabaena azollae occurs as a symbiont of inside the leaves of the freshwater fern, Azolla.
Akinetes can survive desiccation and eventually germinate into a new filament.
Increases the fertility of the soil/water via the action of the heterocysts in fixing free nitrogen.
Anabaena azollae is used in association with the water fern Azolla as an alternate source of nitrogen in wet rice cultivation. This is because the alga has the ability to fix atmospheric nitrogen, providing nitrates to the crop. Generally, the water fern is grown during the fellow period of rice cultivation. The fern can also be used as a green manure in the cultivation of taro (Colacasia esculanta) or wheat (Triticum spp.).
Bold, H. C., C. J. Alexopoulos & T. Delevoryas, 1987. Morphology of plants and fungi. Harper & Row, New York. (5th ed.). 912pp.
Prud’homme van Reine, W. F. & G. C. Trona Jr. (eds.), 2002. Plant resources of South-East Asia No. 15(1). Cryptogams: Algae. Prosea Foundation, Borgor, Indonesia. 318 pp.