Seed Priming with Carrot Extract Improves Early Physiological Responses to Salinity in Rice

Soil salinization is a major constraint on irrigated rice cultivation, mainly due to poor irrigation management and cropping in coastal areas. Seed priming is widely recognized as a cost-effective and practical approach to enhance early growth and improve tolerance to abiotic stresses, including salinity. This study evaluated the effects of seed priming of rice seeds from two cultivars, BRS Querência (Indica) and BRS 358 (Japonica), using aqueous carrot root extract at 0% (water), 25%, and 50% concentrations for 48 h. Seeds were sown in rhizotrons and exposed to 0, 75, or 150 mM NaCl. Morphological, physiological, and biochemical traits were evaluated at 21 days after sowing. Seed priming with carrot extract was associated with improved growth and physiological responses under salinity stress. Under 150 mM NaCl, primed seedlings showed approximately 40% higher chlorophyll index, 35% greater root volume, and 30% higher shoot dry mass compared to unprimed controls. The 25% extract concentration was particularly effective for BRS Querência, which showed enhanced root elongation and a higher nitrogen balance index. Activities of superoxide dismutase, ascorbate peroxidase, and catalase increased by 45-70%, while hydrogen peroxide and malondialdehyde levels decreased by approximately 50%, suggesting enhanced antioxidant responses and improved redox balance. Anthocyanin accumulation also increased in specific cultivar-treatment combinations, suggesting a potential effect on secondary metabolism and antioxidant pathways. Overall, carrot-based seed priming was associated with improved seedling performance, pigment stability, and regulation of oxidative stress under saline conditions. These results suggest that carrot-based seed priming may improve physiological performance under salinity stress.