Abstract

Nostoc spongiaeforme collected from rice-fields of Andhra Pradesh, India, were made unialgal and were used for the present study. The effect of nitrogen sources (NH4CI, KNO3, NaNO2) alone and in combination with 2,4-D herbicide on growth of the algae and uptake and kinetics of nitrogen along with 2,4-D were also examined up to 25 days of life cycle with an interval of 5 days. Uptake of nitrogen alone and in combination with 2,4-D followed Michaelis-Menton Kinetics in Nostoc spongiaeforme. At the beginning of the life cycle, Nostoc spongiaeforme exhibited low Km values which indicated the high uptake of nitrogen. Later, increasing Km values at every successive period of the growing stages of algae indicate the reduction in uptake of nitrogen from the medium suggesting that the algal cells might have absorbed sufficient nitrogen. Nitrogen uptake was high when algal cells were grown in nitrogen containing medium whereas the uptake was comparatively lower when Nostoc spongiaeforme was grown in 2,4-D + nitrogen containing medium.