The Studies On The Protective Roles Of Exogenous NO In Maize Seedlings Under Salt Stress

Nitric oxide (NO) is a key signaling molecule involved in growth, development as well as stress tolerance in plants. In the study, we investigated the protective roles of NO under salt stress in maize seedlings.The main results are following:1. Low concentration NaCl treatment (10 mM) increased the growth of maize seedlings; under 200 mM NaCl treatment, the maize seedlings showed salt tolerance; the higher NaCl stress (300 mM and 450 mM) induced the death of maize seedlings.2. Under 200 mM NaCl treatment for 1,2 or 3 d, the proline content increased with the increasing time in maize seedlings. At day 4, the proline content began to decrease. In SNP+NaCl treatment, exogenous NO could decrease the NaCl-induced proline contents.3. NaCl stress induced H2O2 accumulation in maize seedlings, and which could be abolished buy the addition of exogenous NO. The further study showed that exogenous NO could significantly increase the activities of the antioxidant enzymes (APX, CAT) and the antioxidant contents (GSH). This enhanced antioxidant ability might account for the protective role of NO under salt stress in maize seedlings, which profited to reduced ROS levels.4. Under 200 mM NaCl treatment for 3 d, the activities of nitrate reductase (NR) and glutamine synthase (GS) decreased; and the contents of flavonoid and anthocyanin increased. In SNP+NaCl treatment, exogenous NO could increase the activities of NR and GS as well as anthocyanin contents, which could effectively reduced the damages from salt stress in maize seedlings.