Study on effect of silver nanoparticles synthesized by biological method on on growth and physiological and biochemical properties of Melissa officinalis L.

Using bio nanoparticles plays an important role in increasing agricultural productivity. In recent years, the use of nanoparticles in plants has been considered as pesticides, protective agents and nutrients. Melissa Officnalis L. is a medicinal plant of the family of Lamiaceae, which has antibacterial, anticancer and antiviral properties. In this research effects of different concentrations of silver nanoparticles on some physiological parameters of M. Officnalis L. was performed under pot condition in Basic Sciences Faculty of  University of Zabol, in 2017. Experiment was conducted using randomized complete block design with 3 replications by silver nanoparticles treatment in four concentrations (100, 60, 20, 0 ppm). The results showed that different growth parameters including root and stem fresh weight, root and shoot length and protein content significantly increased under AgNPs, with the highest amount at 60 ppm AgNPs on day 15. Proline and carbohydrate also increased under different concentrations of AgNPs compared to control, with highest content at 100 ppm AgNPs on day 15. The maximum content of secondary metabolites, including phenol and flavonoids, was observed the at 100 ppm AgNPs on day 20. The maximum increase in the anthocyanin content was observed at concentration of 60 ppm AgNPs on day 15. The increased activity of antioxidant enzymes (catalase, guaiacol peroxidase and ascorbate peroxidase) under different concentrations of AgNPs led to a decrease in MDA content. According to the results of this study, AgNPs are suggested as a suitable stimulant for increasing growth and production of secondary metabolites.