Foliar Application of Zinc Oxide Nanoparticles and Salicylic Acid Enhances Drought Tolerance in Tomato by Improving Antioxidant Defence, Nutrient Uptake, and Anatomical Features

This study aimed to explore the impact of foliar use of zinc oxide nanoparticles (ZnO-NPs) and salicylic acid (SA), each at a concentration of 60 mg/L, applied either separately or together, in minimizing the negative outcomes of water shortage stress at 75 and 50% field capacity in tomato (Solanum lycopersicum L.) plants (‘Super Strain B’). The findings revealed that drought stress markedly decreased the content of essential nutrients; nitrogen, phosphorus and potassium, and negatively affected stem anatomical features, including reduced thickness of the cortex, phloem, xylem, and vascular cambium. Nevertheless, the use of ZnO-NPs and SA, either alone or in combination, alleviated these negative impacts by enhancing the activity of key antioxidant enzymes such as superoxide dismutase, catalase, and peroxidase. These treatments also improved nutrient uptake and restored anatomical structures under water stress. To sum up, the findings suggest that foliar use of ZnO-NPs and SA, independently or jointly, enhances antioxidant defense, nutrient accumulation, and stem anatomy in tomato plants under drought conditions, thereby improving plant resilience to water scarcity.