Evaluation of photosynthetic pigments, fluorescence indexes, gas exchange, and some active flavonoid substances in Viola tricolor L. under the effect of bio-silver nanoparticles

Viola tricolor L. of the Violaceae family is used for its antioxidant and pharmaceutical compounds. This study was conducted based on a completely randomized design with four replications to investigate the effect of silver nanoparticles on the photosynthetic systems and gas exchange of the Viola tricolor L. Treatments included silver nanoparticles with three concentrations (10, 50, and 100 ppm) and a control (distilled water). Results of the study showed that relative water content, stomatal conductance, chlorophyll a concentration, and total chlorophyll concentration, maximum fluorescence, soluble carbohydrate, and antioxidant activity were higher in the treated plants compared with the control plants. Stomatal conductance showed a significant improvement under 50 mg/L silver nanoparticles compared with the other treatments. Maximum chlorophyll b was observed in 10 ppm concentration of silver nanoparticles. Moreover, the highest chlorophyll a content was observed in the plants treated with 50 mg/L concentration of nanoparticles. Carotenoid contents significantly improved in the plants treated with silver nanoparticles. CO2 content and insoluble carbohydrate were higher in the control group compared with the other treatments. A number of effective flavonoids were assayed, including Rutin, Quercetin, and Apigenin which showed a significant difference compared with the control group in 10, 50, and 10 ppm treatments, respectively. The results of this study showed that silver nanoparticles stimulate antioxidant activity and increase the secondary metabolites (flavonoid content) of Viola tricolor L.