Gibberellic Acid-Induced Regulation of Antioxidant–Flavonoid Channels Provides Protection Against Oxidative Damage in Safflower Under Salinity Stress

Salinity is a major constraint that compromises safflower performance by disrupting redox balance and metabolic homeostasis. Although hormonal mechanisms for improving plant resilience to abiotic stresses have been reported, the mechanistic role of gibberellic acid (GA3)-induced regulation of safflower tolerance to salinity remains unclear. This study aimed to investigate the impact of exogenous GA3 application under normal and saline conditions to evaluate its effects on growth, physiology, redox regulation, and flavonoid biosynthesis in safflower. Using phenotypic, physiological, biochemical, and gene expression analysis, it is suggested that GA3 significantly alleviates salt stress by integrating antioxidant defense and flavonoid biosynthesis. The results of phenotypic and physiological assessments showed that GA3 at 400 mg/L GA3 in safflower seedlings suggests enhanced vegetative growth and photosynthetic performance. Under salt stress, GA3 significantly alleviated oxidative damage by reducing H2O2, O2−, and malondialdehyde (MDA) levels, while enhancing osmoprotective compounds such as proline, soluble sugars, proteins, and chlorophyll. GA3 also significantly increased the activity of antioxidant enzymes (SOD, POD, CAT, APX, GST, DHAR, and Prx), accompanied by the transcriptional upregulation of their corresponding genes, indicating GA3-mediated regulation of redox homeostasis at both biochemical and molecular levels. In parallel, GA3 enhanced the accumulation of major flavonoids, particularly hydroxy safflor yellow A (HSYA), with strong induction of key HSYA biosynthetic genes (CtF6H, CtCGT, Ct2OGD1), whereas salinity alone suppressed their expression. In contrast, the quercetin branch displayed a regulatory bottleneck at CtF3H, which remained suppressed under all treatments, although upstream genes were GA3-responsive. Together, these findings demonstrate that GA3 enhances salinity tolerance in safflower by simultaneously activating antioxidant defenses and stimulating flavonoid biosynthesis, providing mechanistic insight with practical implications for developing salt-resilient safflower varieties.