Effect of different levels of salicylic acid foliar application on phenols, flavonoids, antioxidant activity, and photosynthetic pigments of peppermint

Peppermint, scientifically known as Mentha piperita, is an aromatic and medicinal plant that belongs to the Lamiaceae family. In the Research Greenhouse of University of Zabol, an experiment was conducted in a completely randomized design with three replications to investigate the effect of salicylic acid foliar application on peppermint. Salicylic acid was sprayed in two stages (8 weeks after stolon set-up and 2 weeks after the first foliar application) at levels of 0, 5, 10, 50, and 100 ppm. Phenols, flavonoids, antioxidant activity, total protein, and physiological traits like catalase, carbohydrate, ascorbate oxidase, peroxidase, polyphenol oxidase, and photosynthetic pigments were all measured in this study. The treatment with different levels of salicylic acid had a significant impact on all studied traits (p ≤0.01) and improved all studied traits except carbohydrates, according to analysis of variance. At a dose of 100 ppm, salicylic acid had the greatest additive effect on physiological and biochemical traits. According to the findings of this study, salicylic acid foliar application on peppermint appears to increase antioxidant compounds, osmotic regulators (carbohydrates), and photosynthetic pigments, and is a promising and cost-effective method for increasing secondary metabolites and medicinal properties of this plant.