Influence of nitrate, phosphate and herbicide stresses on nitrogenase activity and growth of cyaobacteria 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 ul/ mg.h) at lOmM nitrate concentration. At 25mM phosphate concentration, Nodularia showed the highest nitrogenase activity (0.006 ethylene ul/ mg.h ). The highest tolerances for the herbicides were present in Nodularia (0.06 ethylene ul/ mg.h) for bensulphuron (50ug /ml) and Nostoc 6 ethylene ul/ mg.h (for molinate lOOug / ml).