Exogenously Applied Gibberellic Acid Enhances Growth and Salinity Stress Tolerance of Maize through Modulating the Morpho-Physiological, Biochemical and Molecular Attributes

Soil salinity is the major limiting factor restricting plant growth and development. Little is known about the comparative and combined effects of gibberellic acid (GA₃) seed priming and foliar application on maize under salt stress. The current study determined the impact of different application methods of GA₃ on morpho-physiological, biochemical and molecular responses of maize seedlings under three salinity stress treatments (no salinity, moderate salinity-6 dS m^-1, and severe salinity-12 dS m^-1). The GA₃ treatments consisted of control, hydro-priming (HP), water foliar spray (WFS), HP + WFS, seed priming with GA₃ (GA₃P, 100 mg L^-1), foliar spray with GA₃ (GA₃FS, 100ppm) and GA₃P + GA₃FS. Salt stress particularly at 12 dS m^-1 reduced the length of shoots and roots, fresh and dry weights, chlorophyll, and carotenoid contents, K⁺ ion accumulation and activities of antioxidant enzymes, while enhanced the oxidative damage and accumulation of the Na⁺ ion in maize plants. Nevertheless, the application of GA₃ improved maize growth, reduced oxidative stress, and increased the antioxidant enzymes activities, antioxidant genes expression, and K⁺ ion concentration under salt stress. Compared with control, the GA₃P + GA₃FS recorded the highest increase in roots and shoots length (19-37%), roots fresh and dry weights (31-43%), shoots fresh and dry weights (31-47%), chlorophyll content (21-70%), antioxidant enzymes activities (73.03-150.74%), total soluble protein (13.05%), K⁺ concentration (13-23%) and antioxidants genes expression levels under different salinity levels. This treatment also reduced the H₂O₂ content, and Na⁺ ion concentration. These results indicated that GA₃P + GA₃FS could be used as an effective tool for improving the maize growth and development, and reducing the oxidative stress in salt-contaminated soils.