Morphometric, Physiological, and Proteomic Insights into Drought Stress Mitigation in Big Leaf Mahogany: The Role of Defense Hormones JA and SA in Enhancing Stress Resilience

Drought stress is a major abiotic constraint affecting growth and productivity in tropical forestry species such as Swietenia macrophylla (mahogany). This study investigates the morphometric, physiological, biochemical, and proteomic responses of mahogany seedlings to drought and evaluates the ameliorative potential of two defense hormones—Jasmonic Acid (JA) and Salicylic Acid (SA). Seedlings were subjected to three phases: pre-drought (well-watered), drought (25% field capacity), and recovery (rehydration with foliar application of 0.6 mM JA or 0.8 mM SA). Drought stress significantly reduced photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), pigment content, and relative water content (RWC), while enhancing proline and superoxide dismutase accumulation and altering protein expression profiles. Exogenous hormone application mitigated these effects, with JA showing superior efficacy in restoring growth traits, physiological function, and pigment levels compared to SA. Proteomic analysis revealed drought-induced downregulation of photosynthetic and metabolic proteins such as RuBisCO and DAHP synthase, along with upregulation of stress-responsive proteins including Heat Shock Protein 90 (HSP90) and sulfiredoxin. Hormonal treatments reversed these patterns, promoting the accumulation of proteins associated with photosynthesis and stress defense. Gene Ontology (GO) enrichment highlighted the involvement of photosynthetic processes, metabolic reprogramming, and reactive oxygen species (ROS) scavenging in drought adaptation. Overall, the findings demonstrate that JA and SA play complementary roles in alleviating drought stress, with JA being more effective, and provide valuable insights for enhancing stress resilience in tropical tree species through targeted hormonal interventions.