The Utricularia-Cyanophyta association and its nitrogen-fixing capacity

Utricularia inflexa Forsk. growing in a shallow lake near Dar es Salaam, Tanzania was found to be abundantly associated with blue-green algae and other microorganisms, though blue-green algae were not found in the lake water. The epiphytes occurred both on the outer surfaces of the macrophyte and inside its traps. Seven genera of the Cyanophyta were observed, amongst which Anabaena was the most abundantly and consistently associated.Both epiphytes on the outer surfaces of the macrophyte and those inside mature traps fixed nitrogen in situ. Mature parts of the macrophyte fixed nitrogen at higher rates than immature parts, indicating the former was associated with a greater abundance of nitrogen fixers. The Utricularia-Cyanophyta association showed a nitrogen fixation (acetylene reduction) rate of 2012 nmol C₂H₄ g^–1 dry weight h^–1 or, in terms of lake area, of 4 500 nmol C₂H₄ m^–2 h^–1. The relative contributions of blue-green algae and bacteria were not determined.It is proposed that the association may involve a degree of physiological interdependence and that the association has potential as a biofertilizer for rice.Based on an M.Sc. thesis by G. M. Wagner submitted to the Department of Botany, University of Dar es Salaam, 1983.Based on an M.Sc. thesis by G. M. Wagner submitted to the Department of Botany, University of Dar es Salaam, 1983.