Sequenced application of ascorbate-proline-glutathione improves salt tolerance in maize seedlings

• Sequenced application of AsA-Pro-GSH by soaking seeds mitigated the adverse effects of NaCl stress on maize seedlings.
• Growth, endogenous antioxidants and phytohormones increased by AsA-Pro-GSH application to maize.
• Sequenced application of AsA-Pro-GSH protected antioxidant system in maize seedlings.

The role of antioxidants exogenously-applied individually or in sequences in the improvement of salt tolerance in maize seedlings, and their effects on changes in the activities of endogenous enzymatic and non-enzymatic antioxidants, and the concentrations of phytohormones in seedlings grown under 100 mM NaCl stress were assessed. The efficiency of maize seedlings to tolerate salt stress in terms of growth was noticed to varying degrees with antioxidants applied singly or in sequences. The healthy growth of salt-stressed seedlings was correlated with the improvements in the activities of enzymatic and non-enzymatic antioxidants, the concentrations of osmoprotectants and phytohormones, and tissue health in terms of relative water content and membrane stability index. Results show that, seed soaking in AsA, GSH and proline applied in sequences (i.e., AsA0.50-Pro0.50-GSH0.50 or GSH0.50-Pro0.50-AsA0.50) was better than their applications individually. In addition, the sequenced application of AsA0.50-Pro0.50-GSH0.50 as integrated treatment was better, generating maize seedlings more tolerant to salinity than those generated from the sequenced application of GSH0.50-Pro0.50-AsA0.50. Therefore, we recommend using the sequenced application of AsA0.50-Pro0.50-GSH0.50 as integrated soaking treatment for maize to grow under salt stress.