Ascorbic Acid Enhances Growth and Yield of Sweet Peppers (Capsicum annum) by Mitigating Salinity Stress

Salinity is a crucial problem which has affected crop productivity globally. Ascorbic acid is considered helpful against abiotic stresses due to its powerful antioxidant potential. In the pot experiment, salinity stress (0, 35, 70, and 105 mM) was applied to sweet peppers in split doses after 20 days of transplantation. To mitigate the adverse effects of salinity, ascorbic acid (0, 0.40, 0.80, and 1.20 mM) was applied as foliar spray after a 6-day interval during vegetative growth. Sweet pepper plants sprayed with distilled water (control) recorded maximum plant height (cm), leaf area (cm²), number of branches, stem diameter (mm), number of fruit plant⁻¹, fruit diameter (cm), yield plant⁻¹ (g), and chlorophyll content (mg 100 g⁻¹), while the maximum polyphenol oxidase (PPO) activity (unit mg protein⁻¹ min⁻¹) and ascorbate peroxidase (APX) activity (unit mg protein⁻¹ min⁻¹) were recorded in plants treated with 70 mM NaCl application. Salinity stress beyond 70 mM significantly reduced all the studied parameters. An ascorbic acid concentration of 1.20 mM significantly mitigated the negative effects of salt stress and recorded maximum plant height (cm), number of leaves plant⁻¹, leaf area (cm²), number of branches plant⁻¹, stem diameter (mm), number of fruit plant⁻¹, fruit diameter (cm), yield plant⁻¹ (g), chlorophyll content (mg 100 g⁻¹), PPO activity (unit mg protein⁻¹ min⁻¹), and APX activity (unit mg protein⁻¹ min⁻¹). Hence, a 1.20 mM concentration of foliar ascorbic acid could be used in saline conditions up to 70 mM of sodium chloride (NaCl) for better growth, productivity, and enzymatic activity of sweet peppers.