Glycine-betaine induced salinity tolerance in maize by regulating the physiological attributes, antioxidant defense system and ionic homeostasis

The plants are exposed to different abiotic stresses, including the salinity stress (SS) that negatively affect the growth, metabolism, physiological and biochemical processes. Thus, this study investigated the effect of diverse levels of foliar-applied GB (0 control, 50 mM and 100 mM) on maize growth, membrane stability, physiological and biochemical attributes, antioxidant enzymes and nutrients accumulation under different levels of SS (i.e., control, 6 dS m⁻¹, 12 dS m⁻¹). Salt stress diminished the root and shoot length, root and shoot biomass, chlorophyll contents, photosynthetic rate (Pn), stomatal conductance (gs), relative water contents (RWC), soluble proteins (SP) and free amino acids; (FAA); and increased activities of antioxidant enzymes, electrical conductivity (EC) and accumulation of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), Na⁺ and Cl⁻ ions. GB application significantly increased root and shoot growth, leaves per plant, shoots length, chlorophyll contents, gs, Pn and membrane stability by reducing MDA and H₂O₂ accumulation. Moreover, GB also increased the SP, FAA accumulation, activities of antioxidant enzymes and Na⁺ and Cl⁻ exclusion by favouring Ca²⁺ and K⁺ accumulation. In conclusion, the foliar-applied GB increased Pn, gs, ant-oxidants activities, and accumulation of SP and FAA; and reduced the accretion of Na⁺ and Cl⁻ by favouring the Ca²⁺ and K⁺ accretion which in turns improved growth under SS.