Studies with phorate, an organophosphate insecticide, on growth, nodulation and on some enzymes of nitrogen metabolism in black gram

The effect of phorate on growth behaviour, nodulation and activity of enzymes of nitrogen metabolism, viz., nitrogenase (N₂-ase), glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) in the root nodules of black gram was studied. Phorate stimulated growth of root and shoot, number of nodules per plant, activity of these enzymes at lower concentration but decreased their activity at higher concentrations. Apparent Km values of N₂-ase, GS, GOGAT and GDH were similar in the control and the treated plants indicating that the treatment affected the synthesis or turnover of these enzymes rather than their activity.