Mitigation of salt stress in maize seedlings by exogenous proline application

The mitigation effect of exogenous proline (Pro) application on salt stress was investigated in maize seedlings with different resistance levels using a salt-tolerant inbred line 8723 and salt-sensitive inbred line P138. The effects of exogenous Pro application on the growth parameters and related physiological indexes of maize seedlings under salt stress were studied under conditions of 180 mmol·L⁻¹ NaCl and 250 μmol·L⁻¹ exogenous Pro. The results showed that exogenous Pro treatment can effectively alleviate the inhibitory effect of salt stress on roots and shoots growth of maize seedlings, and increase the activities of superoxide dismutase, peroxidase, and catalase, as well as the levels of osmotic solute Pro and soluble sugars, reduce the content of malondialdehyde, and stabilize the structure of cell membranes. Exogenous Pro addition could also strengthen the intracellular ion balance and reduce the toxic effect of Na⁺ on maize seedlings. In addition, exogenous Pro had a better mitigation effect in the salt sensitive variety. The above results indicated that exogenous Pro could alleviate the effect of salt stress damage on maize seedlings by regulating antioxidant enzyme activities and osmotic solute and ion nutrient balances, thereby improving its salt tolerance.