Comprehensive biochemical and physiological characterization of Moringa oleifera L. under drought stress conditions

Drought stress is a major abiotic factor that adversely affects plant growth, metabolism, and productivity. This study aimed to investigate the biochemical and physiological responses of Moringa oleifera under varying levels of drought stress. Four-week-old seedlings were subjected to three soil moisture regimes: Control (100% field capacity), Moderate stress (50%), and Severe stress (25%) for 21 days. Fifteen key parameters were analyzed, including antioxidant enzymes (SOD, CAT, POD, APX, GR), oxidative stress markers (MDA, H₂O₂, electrolyte leakage), osmolytes (proline, TSS), photosynthetic pigments (chlorophyll a, b, total), and secondary metabolites (total phenolics and flavonoids). Results showed a significant upregulation of antioxidant enzyme activities under drought, with SOD, CAT, and GR increasing markedly under severe stress, indicating enhanced ROS detoxification. Oxidative stress markers such as MDA and H₂O₂ were elevated, along with increased membrane leakage, suggesting lipid peroxidation and loss of membrane stability. Proline and soluble sugars increased substantially, supporting their role in osmotic adjustment and stress mitigation. Conversely, chlorophyll content declined sharply under drought, reflecting compromised photosynthesis. The accumulation of total phenolics and flavonoids was notably higher in stressed plants, suggesting activation of the phenylpropanoid pathway for antioxidant defense. The findings highlight Moringa oleifera's robust biochemical and physiological adaptations to water deficit, emphasizing its potential as a drought-resilient species. Traits such as enhanced enzymatic activity and osmolyte accumulation may serve as effective biomarkers for screening drought-tolerant genotypes. This study provides valuable insights for future crop improvement strategies in arid and semi-arid agroecosystems.