Effect of pre-incubation of nitrate and ammonium in cultures on nitrate reductase activity in marine red algae <i style="">Gelidiella </i>and <i style="">Gracilaria </i>from southeast coast of India

Abstract

232-236Nitrate reductase (NR) activities of six agar yielding seaweeds viz. Gelidiella acerosa, Gracilaria corticata, G. crassa, G. edulis, G. foliifera and G. verrucosa pre-incubated in different concentrations (150, 300, 450, 600 and 750 µmol/l) of nitrate (NaNO3) and ammonium (NH4)2S2O8 (700, 1400, 2100, 2800 and 3500 µmol/l) were studied. NR activity ranged from 0.07 to 24.72 mmol/g (f.wt)/h in G. acerosa; 0.19 to 5.83 mmol/g (fr.wt.)/h in G. corticata; 0.23 to 9.99 mmol/g (fr.wt.)/h in G .crassa; 0.06 to 0.43 mmol/g (fr.wt.)/h in G. edulis; 0.37 to 19.92 mmol/g (fr.wt.)/h in G. foliifera and 0.74 to 10.54 mmol/g (fr.wt.)/h in G. verrucosa. Maximum NR activity was found at an optimum nitrate concentration of 600 µ mol/l in all five species of Gracilaria and at 450 µmol/l in Gelidiella acerosa. Nitrate enhanced NR activity in all six species of agarophytes. Ammonium suppressed NR activity in all algae except G. edulis in which no obvious difference was observed in NR activity between NO3 and NH4 added culture