Integrated Molecular Defense Mitigating Salt Stress in Tomatoes Using Synergistic Signaling Molecules

Salt stress severely compromises agricultural productivity worldwide, necessitating innovative defense strategies. While individual signaling molecules can enhance stress tolerance, their combined potential remains largely unexplored. This study introduces a novel triple-defense approach, investigating the synergistic effects of three signaling molecules (30 mM KNO₃, 0.2 mM H₂O₂, and 30 mM CaCl₂) in mitigating 100 mM NaCl-induced salt stress in tomato plants. Our comprehensive analysis revealed that salt stress significantly impaired plant growth parameters, including height, leaf SPAD value, biomass accumulation, and essential nutrient concentrations (K, Ca, Mg, S) in both leaves and roots. Salt stress also disrupted water relations and triggered oxidative stress, evidenced by increased sodium accumulation, hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) levels. The strategic application of signaling molecules, particularly in combination, effectively counteracted these stress-induced alterations. KNO₃ emerged as the most potent individual defender, followed by CaCl₂ and H₂O₂, enhancing growth characteristics and antioxidant defense mechanisms through increased catalase (CAT) and ascorbate peroxidase (APX) activities. Notably, the simultaneous application of all three compounds demonstrated superior efficacy in alleviating salt stress impacts, establishing a robust defense mechanism through improved osmolyte accumulation (proline, soluble sugars) and reduced oxidative damage. This triple-defense strategy presents a promising approach for enhancing salt stress tolerance in tomato cultivation.