Effect of nitrate nutrition on growth and nitrogen assimilation of pearl millet exposed to sodium chloride stress

Influence of nitrate concentration on growth and nitrogen assimilation in salinity-stressed pearl millet (Pennisetum typhoids L.) was studied. The plants were grown in perlite and irrigated with nutrient solution containing 0, 25, 50, or 100 mM sodium chloride (NaCl) in the presence of 2 or 10 mM NO3-. Salinity decreased leaf dry weight and soluble proteins, as well as total chlorophyll. Free amino acid content, including proline, was higher in salt-stressed plants compared to controls. The activities of nitrate reductase, nitrite reductase, and glutamate synthase were reduced, but the glutamine synthetase activity was less affected. High nitrate (10 mM) in the irrigation solution partially restored activities of the above enzymes and increased the soluble protein content despite the high NaCl concentration. The retarded growth of pearl millet due to salinity stress was partially restored in the presence of high nitrate concentration in the irrigation solution.