Original paper

Growth response and acetylene reduction activity of two nitrogen fixing cyanobacteria to commercial fertilizers

Sahu, Jayanta Kumar; Adhikary, Siba Prasad


Changes in the growth and nitrogenase activity (acetylene reduction activity, ARA) of two heterocystous cyanobacteria in response to various doses of the commercial fertilizers, e.g. Urea, ammonium sulphate, muriate of potash (MOP) and single super phosphate (SSP) was studied. Fertilizer concentration dependent reduction in chlorophyll-a content and ARA of both the organisms was observed. Recommended dose of the nitrogenous fertilizer inhibited the ARA, however, the threshold value of N-fertilizer to inhibit the growth was much higher than for nitrogen fixation. When both the organisms were exposed to recommended and EC 50 doses of different fertilizers for 3 or 6 days and subsequently grown in fertilizer free medium for a further period of 3 or 6 days, grew better than the fertilizer treated culture and revived their nitrogenase activity showing a temporary repression of nitrogen fixation in presence of the commercial fertilizers.


cyanobacteriarice fieldfertilizerchlorophyll-aacetylene reductiontolerancerecovery