Gibberellic acid modulates drought stress signaling, antioxidant defense, and ionic homeostasis in spinach

Drought stress is a major environmental signal that disrupts plant growth and metabolic homeostasis, particularly in water-sensitive leafy vegetables, such as spinach (Spinacia oleracea L.). Plant hormones play a central role in decoding stress signals and coordinating adaptive responses. This study investigated the role of exogenous gibberellic acid (GA) in regulating drought-induced physiological, biochemical, and ionic signaling in spinach. A pot experiment was conducted using two spinach cultivars (V1 = Desi, V2 = Lahori) subjected to well-watered and drought conditions (50% field capacity), combined with foliar GA applications (0, 100, and 200 ppm). Drought stress markedly altered plant behavior by suppressing growth traits, photosynthetic pigment synthesis, and redox balance, while increasing reactive oxygen species accumulation. GA application, particularly at 200 ppm, significantly modulated drought stress signaling by activating antioxidant defense systems [CAT (51.1%), POD (44.2%), and SOD (42.6%)], reducing oxidative damage indicators [H₂O₂ (3.6%) and MDA (25.3%)], and restoring metabolic stability. In addition, GA regulated ionic homeostasis by limiting Na⁺ (11.2%) accumulation and promoting K⁺ (96.6%) and Ca²⁺ (46.3%) uptake in both roots and shoots, reflecting improved stress adaptation. Cultivar-specific responses indicated higher signaling sensitivity and adaptive capacity in the Desi variety under drought stress. Overall, these findings demonstrate that gibberellic acid acts as a key regulatory signal that orchestrates antioxidant, metabolic, and ionic responses, thereby increasing drought stress adaptability in spinach.