English

Abstract

Cyanobacteria offer an economically and ecologically sound alternative to chemical fertilizers for realizing the ultimate goal of increased productivity, especially in rice cultivation. There is however, a growing concern about the adverse effects of indiscriminate use of chemical fertilizers on soil productivity and environmental quality. A comparative study between the NR activity and biomass of six Anabaena strains isolated from paddy field soils of Ganjam district in presence of pH, temperature, copper& molybdenum, NaNO 3, NH 4Cl, and Urea is being conducted to present a situation where NR activity and biomass may be affected under varied concentration. Maximum NR activity was observed in Anabaena sp. at pH 8.5 and 35 o C temperature while Anabaena circinalis showed minimum activity in same concentration. Biomass content was maximum in Anabaena variabilis at pH 8.5 where as at temperature 35 o C in Anabaena flos-aquae and minimum biomass observed in Anabaena iyengarii at same concentration. NR activity in relation to copper was maximum in Anabaena sp. at 2 �g/l while minimum in Anabaena circinalis at same concentration. At 0.5µg/l molybdenum content in the culture medium showed maximum NR activity in Anabaena sp and reduced in all strains with increase of concentration. Anabaena flos-aquae showed minimum NR activity at 0.1mM concentration of NaNO 3 while Anabaena circinalis showed minimum NR activity at same concentration of NH 4Cl. The NR activity was observed minimum at 3mM concentration of Urea in A. cylindrica . The activity of NR and biomass in all the strains was influenced by external NH 4 - and NO 3