Effect of Ag Nanoparticles on Morphological and Physio-biochemical Traits of the Medicinal Plant Stevia Rebaudiana

Nowadays, overproduction of secondary metabolites in remedial herbs through giving biotic/abiotic stresses is an interesting area of research. In the current study, the influences of various concentrations of silver nanoparticles (Ag NPs) were evaluated on several morphological and physio-biochemical traits, such as the steviol glycosides level in Stevia. The findings showed that the herbs incubated with 400-ppm Ag NPs own the highest dry and fresh weight of shoot, while those incubated with 80- up to 200- ppm Ag NPs own the highest steviol glycosides content. As a result, we successfully improve the content of stevioside glycoside up to 1.75-fold by applying the 80- up to 200-ppm Ag NPs in Stevia medicinal plant. Moreover, our findings revealed that low concentrations the Ag NPs lead to an increase of glutathione content and total antioxidant capacity, and a decrease of MDA, whereas treatments at higher concentrations induced adverse effects for the plant. As a result, the treatment with Ag NPs low concentrations had a favorable efficacy on physio-biochemical and morphological characteristics of Stevia. These achievements are very promising, because they revealed a considerable capability for the Ag NPs application in enhancing the secondary metabolites in Stevia remedial herb. The present study is the first case assessing the desirable influences of Ag NPs on the Stevia, in regard with shifting of biosynthetic pathway of steviol glycosides in a concentration-dependent manner.