Hydrogen peroxide and salt stress in radish: effects on growth, physiology, and root quality

Hydrogen peroxide (H₂O₂) plays a central role in responses to salt stress, a major abiotic stress that impacts crop yield worldwide. Despite the evidence that H₂O₂ mitigates salt stress and improves post-harvest quality on several species, its effects on radish were not investigated so far. Thus, the objective of this study was to evaluate the exogenous application of H₂O₂ on salt stress mitigation of radish growth, physiology, and post-harvest quality. For this, radish plants were grown in pots for 30 days, being watered with non-saline (0.31 dS m⁻¹) or saline water (120 mM NaCl, 12.25 dS m⁻¹). Plants were leaf-sprayed weekly with water (control – 0 µM H₂O₂) or H₂O₂ (150 or 1500 µM) solutions. The experimental design was completely randomized in a 3 × 2 factorial scheme (H₂O₂ treatments × salt stress conditions). The growth, physiology (gas exchanges, photochemical efficiency, relative water content, electrolyte leakage, and the contents of chlorophylls and carotenoids), and post-harvest attributes of globular roots (color, anthocyanins, vitamin C, phenolic compounds, and soluble solids) were determined. Salt stress decreased gas exchanges and increased electrolyte leakage, which resulted in stunted radish growth, and increased the contents of antioxidants, such as anthocyanins, soluble solids, and vitamin C, improving globular root quality. Conversely, H₂O₂ did not mitigate salt stress effects on radish growth, photosynthetic capacity, and oxidative damages. Although H₂O₂ increased vitamin C under non-stressed condition, it was decreased under salt stress. Thus, we conclude that H₂O₂ did not mitigate salt stress on radish growth and quality.