Comparison of Morphological, Biochemical and Enzymatic Responses of Some Capsicum Species to Drought Stress during Developmental Stages

Drought, an important abiotic stress factor, has a profound effect on plant growth, especially in arid and semi-arid regions. This study investigated the interactive effects of drought stress [100, 75, 50 and 25% Field Capacity (FC)] and plant development stages (20, 40 and 60 days after flowering) on pepper species (Capsicum annuumL. and Capsicum chinense Jacq.). The results show that drought affects plant morphology and reduces photosynthetic pigments while increasing phytochemicals [total phenolics (TPh), total flavonoids (TFv) and total antioxidant activity (TAa)], malondialdehyde (MDA), protein, proline, and antioxidant enzymes [catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD)] (P ≤ 0.05). Throughout plant development, a decrease in photosynthetic pigments and phytochemicals was observed, accompanied by an increase in biochemical components and antioxidant enzymes. The photosynthetic pigments of C. annuum were less affected by drought. Extreme irrigation conditions (25 and 100% FC) caused significant phytochemical changes. With increasing drought stress severity, C. annuum showed significantly higher biophysical and enzymatic values compared to C. chinense. Different stress conditions resulted in significantly higher increases in SOD, POD and CAT levels in C. annuum compared to C. chinense at all growth stages, with average increases of 1.40-fold, 1.25-fold and 1.75-fold, respectively. In addition, antioxidant enzyme activities were significantly higher in C. annuum with increasing stress severity, helping to cope with oxidative stress. In conclusion, C. annuum shows more stable morphological, physiological and biochemical performances compared to C. chinense, establishing itself as a more drought-tolerant species.