Exogenous selenium alleviates salt stress in rice seedlings by improving growth and antioxidant defenses

Abstract

Salt stress severely affects the growth and physiological characteristics during the early growth stages of rice (Oryza sativa L.). This study aimed to investigate the potential impact of exogenous selenium (Se) in mitigating the adverse effects of salt stress during rice germination and seedling establishment. At the germination stage, seeds were incubated for nine days under either non-stress (control) or 100 mM NaCl stress conditions, with or without Se supplementation. At the seedling stage, rice plants were grown hydroponically in nutrient solution under control or 100 mM NaCl conditions, again with or without Se. The results revealed that NaCl-stressed rice plants markedly compromised germination indices and plumule growth and reduced photosynthetic pigment contents. Under salt stress, rice plants also exhibited enhanced H₂O₂ accumulation, elevated lipid peroxidation measured as malondialdehyde (MDA) level, and increased activities of antioxidant enzymes - peroxidase (POD) and ascorbate peroxidase (APX). In contrast, exogenous Se application significantly improved germination indices, and seedling growth under salt stress. Selenium treatment also enhanced chlorophyll and carotenoid synthesis and boosted antioxidant enzyme activities while suppressing the accumulation of H₂O₂, thereby protecting against oxidative damage. Furthermore, exogenous Se alleviated membrane injury under saline stress, as reflected by significantly lower MDA levels in stressed seedlings. Finally, these findings suggest that exogenous Se enhances salt stress tolerance in rice by strengthening antioxidant defense responses and reducing oxidative damage during early growth stages.