Anabaenaazollae is a symbiont of the small aquatic fern, Azolla. Economic importance includes Salvinia species used as cultivated ornamentals (some species are weeds of water bodies) and use of Azolla to control mosquitoes (by covering the water surface), as animal fodder, and as a “seeded” addition to rice paddies, enhancing rice growth by release of nitrogens from symbiotic cyanobacteria. Azolla has been used as “green manure” in several countries to fertilize rice paddies and to increase rice yields (van Hove and Lejeune, 2002). All the species of the genus harbour in their fronds a filamentous N 2 -fixing cyanobacterium until now referred as Anabaena azollae (Nostocaceae) (Papaefthimiou et al., 2008). Moreover, an overall decrease (up to 70%) in GS activity in the Azolla cyanobiont has also been shown, that limits the ammonia assimilation in heterocysts. (1997), Giller (2001). The mature cavity, ellipsoid in shape, has the interior surface covered by a mucilaginous layer delimited by an envelope, where 2000–5000 cyanobacterial cells are embedded and immobilized. Nitrogen fixation protein NifU. This situation is different from other cyanobacterial symbioses such as inGunnera, Blasia andAnthoceros, where physiological modifications are reported in the symbiosis with another photosynthetic partner such as the absence of O2 evolution and the absence of photo-fixation of CO2 in the cyanobionts. 1 - 7 of 7. In sharp contrast to the tropical rice paddy ecosystem, biological soil crusts are highly specialized photosynthetic communities of cyanobacteria, algae, lichens, and mosses that are commonly found in arid and semiarid environments throughout the world (Belnap and Lange, 2003). Other notable constraints to Azolla growth are temperature (both high and low temperatures inhibit growth), high water requirement, and pests and diseases (Giller, 2001). Epidermal cells inside the leaf cavity of Azolla project inwards forming numerous multicellular hairs wit… Strasburger, E. 1873 ÜberAzolla. 1913 Über die Assimilation des freien Stickstoffs durch Azolla. This property of nitrogen fixation has made Azolla extremely important economically in the cultivation of … In order to investigate the mechanism of nitrogen fixation, Anabaenaazollae has been isolated from Azolla and cultured separately in synthetic media. Because of rapid wetting and drying, the N2 fixed tends to be released quickly and provides immediate benefit to the vascular plants in the surrounding ecosystem. SEM image of Azolla surface. Stewart, W. D. P., Haystead, A. and Pearson, H. W. 1969 Nitrogenase activity in heterocysts of blue-green algae. Ecol. Several trichomes, traditionally called hairs, protrude from the cavity surface into the mucilage layer and create an intimate contact between the symbiotic partners helping in the exchange of metabolites. It is suggested that by selection (domestication) more efficient strains (clones) can be obtained, and further that with more advanced techniques such as gene mutation and genetic manipulation even more efficient and for agriculture more beneficial clones can be obtained. Microbiology. © 2020 Springer Nature Switzerland AG. Contamination of aquatic ecosystem is perpetually increasing due to release of waste and discharges (having major proportion of toxic heavy metals) from numerous industries that affect the growth and survival of the primary producers of aquatic ecosystem. Bull. Thus the thick mat produced helps to reduce the volatilization of ammonia in rice fields. Moreover, Azolla has a high rate of multiplication, which helps in covering very rapidly the surface of water bodies where it is growing. Of water U.S., June 1974, vol.2, pp 345–373, Intern reported. 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