Herbicidal effect on some metabolic processes of Azotobacter chroococcum.

The effect of pyramin (1-phenyl-4-amino-5-chloro-piridazone-6) and venzar (3-cyclohexyl-5,6-trimethyleneuracil) on growth, oxygen uptake and nitrogenase activity was examined. The possibilities of herbicide accumulation in cells and binding by mucopolisaccharides were also tested. Stimulation of growth was observed in the presence of pyramin (20 and 100 ppm) but no influence of venzar was found. Venzar was found to penetrate into the cells. Pyramin did not penetrate into the cells but its content decreased in cultures of Azotobacter strains. However, no degradation products of pyramin were found. Pyramin was detected in mucopolisaccharide fractions in range 0.2-47 micrograms of Pyrazon per 100 mg. Pyramin and venzar reduced the acetylene reduction rate of crude extracts by 50% when doses of active substances were equal to the weight of crude extract protein contents. Doses required for similar effect in living cells were however more than fourteen times higher. Addition of polivinylpyrrolidone and albumin protected the N2-ase from negative effect of pyramin and to a lesser degree from that of venzar.