Phenylalanine coordinates antioxidant responses and ion homeostasis to enhance salinity tolerance in maize

Salinity stress poses a significant challenge to the productivity of maize, adversely affecting crop growth and development. The present study was conducted to elucidate the potential protective role of phenylalanine against salinity stress by modulating morphological traits, antioxidant defense mechanisms, and ionic balance. The study comprises two factors, including (i) salinity stress: NS = No salinity (control) SS = Salinity stress at 100 mM (sodium chloride), and phenylalanine foliar applications: NS = No spray, DWS = Distilled water spray, PAN10 = 10 mM, PAN20 = 20 mM, PAN30 = 30 mM, and PAN40 = 40 mM spray of phenylalanine. The results revealed that salinity stress caused a significant reduction in the morphological attributes (SFW by 47% and RFW by 39%) and photosynthetic pigments (chlorophyll a by 14% and chlorophyll b by 8%), while the foliar-applied PAN40 ameliorated the stress induce toxicity and improved these morphological attributes by 49% and 43% and photosynthetic pigments by 32% and 47%, respectively as compared to control conditions. Salinity stress increased the production of stress indicators such as MDA by 10% and H₂O₂ by 19%, while foliar application of PAN40 improved the activities of enzymatic and non-enzymatic antioxidants such as POD by 38%, CAT by 36%, and AsA by 38% and reduced the production of MDA by 10% and H₂O₂ by 19% under salinity stress. In crux, the foliar-applied PNA (40 mM) showed better performance under stress by improving the morphological and biochemical attributes to cope with the toxic effects of stress. The application of PAN may serve as a scalable, sustainable strategy to impart salinity stress tolerance in maize, improving both agronomic and biochemical resilience.