Coumarin-mediated modulation of growth, antioxidant enzymes, phenolic metabolism, and DNA methylation in salt-stressed Ocimum basilicum L․

Abstract

Salt stress poses a significant threat to the growth and productivity of Ocimum basilicum (sweet basil), causing adverse effects on physiological and biochemical processes. This study investigated the role of coumarin (COU) at 50 and 100 ppm in mitigating the detrimental effects of salt stress at 50 and 100 mM NaCl. Salt stress led to a noticeable decrease in plant height, stem fresh weight, leaf fresh weight, and SPAD values. However, COU application, particularly at 100 ppm, improved these parameters, mitigating the stress-induced damage. Antioxidant enzyme activity was also influenced, as catalase (CAT) activity increased under salt stress, with further enhancement following COU treatment, especially at 100 ppm. Conversely, ascorbate peroxidase (APX) activity increased under moderate salt stress but decreased under severe stress, while COU partially restored its activity. Rosmarinic acid content, the predominant phenolic compound, increased under salt stress and was further elevated by COU treatment, particularly at 100 ppm. Additionally, DNA methylation patterns exhibited lower polymorphism under 50 ppm COU, while 100 ppm COU combined with high salinity resulted in higher polymorphism. Overall, COU application enhanced salt tolerance by improving growth, stimulating antioxidant enzyme activity, regulating phenolic compound biosynthesis, and modulating DNA methylation patterns, suggesting its potential as a natural elicitor for stress mitigation in basil.