Exogenous Allantoin Enhances Maize (Zea mays L.) Resilience to Salinity Stress: Physiological and Biochemical Insights

Salinity is a major abiotic stress limiting maize growth and productivity worldwide by imposing oxidative stress, impairing photosynthesis and osmotic imbalance. Here, we demonstrate that the exogenous application of 0.5 mM allantoin markedly enhances maize (Zea mays L.) seedling resilience under salinity, effectively restoring germination and vigor, promoting post-germinative growth, and increasing plant height and biomass. Furthermore, allantoin simultaneously decreased oxidative damage by repressing lipid peroxidation and ROS accumulation and increased stress resilience by increasing antioxidant enzyme activities, maintaining chlorophyll and anthocyanin levels, and promoting proline and protein accumulation. Multivariate analysis revealed coordinated regulation of growth, oxidative stress, and metabolic responses, with allantoin-treated seedlings exhibiting an intermediate, stress-adaptive phenotype between those of control and salt-stressed plants. Collectively, these findings reveal that allantoin is a potent modulator of stress tolerance, with promising implications for improving crop performance in saline environments.