Role of nitric oxide in saline stress: Implications on nitrogen metabolism

The present work is focused on the possible relationship between nitric oxide and the induction of nitrogen metabolism in response to salt stress. The plants were subjected to 100 mM NaCl and sodium nitrite (NaNO2) or sodium nitroprusside (SNP) as the NO donor. On one hand, plants showed lower Na+ and Cl- accumulation after application of SNP or NaNO2 together with the NaCl treatment in leaves and roots of tomato. On the other hand, nitrate accumulation can be more important under SNP + NaCl and NO2 + NaCl than NaCl treatment alone. Further results proved that NO significantly enhanced the activities of nitrate reductase (NR, EC 1.6.1.6) and glutamine synthetase (GS, EC 6.3.1.2), both of which separately contributed to the delay of ammonium accumulation in tomato plants under salt stress. Meanwhile, the glutamine synthetase (GS) activity was apparently enhanced by NO. Therefore, these results suggested that NO could strongly protect tomato plants from toxic damage caused by salt stress. Key words: Solanum lycopersicom, salt stress, nitric oxide, nitrogen metabolism.