Exogenous Tyrosine Priming Enhances Salt Stress Tolerance in Rice (Oryza sativa L.)

Salt stress is a key abiotic stressor that contributes to reduced global rice production, particularly in salt-sensitive varieties such as Oryza sativa. This study aimed to assess the possibility of exogenous tyrosine (Tyr) seed priming in mitigating salt stress in rice seedlings (IR64 cultivar). The seeds were subjected to four treatment groups: control (water), 25 mM NaCl (salt stress), 5 mg l⁻¹ tyrosine, and 5 mg l⁻¹ tyrosine + 25 mM NaCl. Key morpho-physiological and biochemical parameters were measured after 14 days. Salt stress significantly inhibited seedling growth, decreased photosynthetic pigments, and elevated malondialdehyde (MDA) levels, indicating oxidative stress. In contrast, tyrosineprimed seedlings under salt stress exhibited notable improvements in seedling length (54.89%), fresh weight (58.88%), and dry weight (50%) relative to salt-stressed plants alone. Photosynthetic pigment levels, particularly total chlorophyll, improved by 55.88%, suggesting preserved chloroplast function. Moreover, tyrosine priming significantly decreased MDA content and increased superoxide dismutase (SOD) activity by 2.03-fold, indicating enhanced antioxidative defense. These findings support the role of tyrosine as a stress-mitigating priming agent, likely due to its function as a precursor for secondary metabolites and its involvement in redox signalling pathways. This study provides novel insights into tyrosine-mediated stress amelioration and suggests its applicability as a sustainable strategy to enhance salt tolerance in rice. Further field-scale studies are warranted to validate these findings under agronomic conditions.