Effect of cultural conditions on biomass and nitrate reductase activity in six strains of anabaena isolated from paddy field soils of Ganjam (Orissa)

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