Foliar Application of Salicylic Acid and Jasmonic Acid Enhances Drought Tolerance in Sesame (Sesamum indicum L.) by Modulating Antioxidant Defense, Photosynthetic Efficiency and Seed Yield

Drought stress poses a significant threat to sesame (Sesamum indicum L.) productivity, yet the potential of plant growth regulators (PGRs) to mitigate its effects remains underexplored. This study investigated the impacts of foliar-applied salicylic acid (SA) and jasmonic acid (JA) on sesame under varying drought intensities over two growing seasons (2022–2023). A split-plot design was employed with three irrigation regimes (25%, 50%, and 75% soil moisture depletion) and seven PGR treatments (SA at 0.5, 1, and 1.5 mM; JA at 50, 100, and 150 µM; and a control). Severe drought increased catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) activities by up to 10%, alongside elevated ion leakage (49.88%) and malondialdehyde (MDA) (10.59 µmol g⁻¹ FW), while reducing relative water content (RWC) to 57.32%. SA at 1.5 mM enhanced CAT (1.66 µmol mg⁻¹ protein min⁻¹), chlorophyll a (1.80 mg g⁻¹ FW), carotenoids (0.450 mg g⁻¹ FW), and seed yield by 8% (752 kg ha⁻¹), while JA at 100 µM reduced ion leakage to 44.05% and boosted proline to 1.81 µmol g⁻¹ FW under 75% depletion. Both PGRs mitigated H₂O₂ accumulation, with SA 1.5 mM achieving the lowest level (1.71 mg g⁻¹ FW). These findings highlight SA’s role in photosynthetic protection and JA’s contribution to osmoprotection, offering concentration-specific strategies to enhance sesame resilience and productivity in drought-prone environments.