Influence of Nitrate, Phosphate and Herbicide Stresses on Nitrogenase Activity and Growth of Cyanobacteria Isolated from Paddy Fields*

Abstract

Samples were collected from paddy fields in Corum-TURKIYE. Nitrogen-free BG-11 medium was used for isolation of
nitrogen fixing cyanobacteria. Acetylene reduction technique was used to determine the effects of different chemical agents
on the nitrogenase activities of the cyanobacteria, which were identified at the genus level. Nodularia showed the highest
nitrogenase activity (0.006 ethylene μl/ mg.h) at 10mM nitrate concentration. At 25mM phosphate concentration, Nodularia
showed the highest nitrogenase activity (0.006 ethylene μl/ mg.h ). The highest tolerances for the herbicides were present in
Nodularia (0.06 ethylene μl/ mg.h) for bensulphuron (50μg /ml) and Nostoc 6 ethylene μl/ mg.h (for molinate 100μg / ml).