Stress signaling and physiological modulation by glycine betaine for cadmium-resilient maize

Glycine betaine (GB), a naturally occurring osmoprotectant, stabilizes proteins, membranes, and osmotic balance under abiotic stress. It effectively mitigates oxidative damage and maintains redox homeostasis, making it a promising candidate for cadmium (Cd) tolerance. Cd toxicity is a major constraint to sustainable agriculture due to its phytotoxicity and bioaccumulation. This study evaluates the effect of GB applied via seed priming and foliar spray on Cd stress in two maize cultivars with contrasting tolerance ( CZP and MMRI). Plants were exposed to 500 mM CdCl₂ under controlled conditions, and morpho-physiological and biochemical traits - including biomass, chlorophyll, protein, reactive oxygen species (ROS), malondialdehyde (MDA), hydrogen peroxide (H₂O₂), proline, GB, soluble sugars, phenolics, and flavonoids - were measured. Cd exposure reduced biomass, chlorophyll, and protein, while increasing ROS, MDA, and H₂O₂. Treatments, particularly seed priming, enhanced osmoprotectants and antioxidants, restoring osmotic balance and redox homeostasis. CZP showed greater biochemical resistance and lower Cd translocation than MMRI. Overall, GB-mediated stress modulation involves physiological reprogramming, with seed priming proving more effective than foliar spray. This study provides novel insights into GB-driven amelioration of Cd stress in maize.