Freshwater depletion becomes a significant challenge as the population grows and food demand rises. We evaluated the responses of lettuce cultivars (Lactuca Sativa) under saline stress in photosynthetic responses, production, and ion homeostasis. We used a randomized block design in a 3 × 5 factorial scheme with five replications—the first factor: three cultivars of curly lettuce: SVR 2005, Simpson, and Grand Rapids. The second factor consisted of five treatments: T1—control (water of 0.53 dS m−1); T2—saline stress (water of 4.0 dS m−1); T3—saline stress + ascorbic acid; T4—saline stress + gibberellic acid; and T5—saline stress + salicylic acid. The Grand Rapids lettuce cultivar tolerated water salinity, obtaining the highest production. The Simpson lettuce cultivar was sensitive to salinity, reducing biomass production under saline stress by 11.47% compared to Grand Rapids. Salicylic acid was more effective at mitigating saline stress in the Simpson lettuce cultivar than ascorbic and gibberellic acids, with a 24.85% increase in production compared to saline stress. The findings suggest that the Grand Rapids lettuce cultivar is more resilient to saline conditions, while salicylic acid can significantly enhance production in the sensitive Simpson cultivar under saline stress.
