Application of signal molecules are very potential elicitors for production of plant secondary metabolites. This study was performed to elucidate the potential impacts of different concentrations of nano-silver (NS: 20, 40 and 80 mg l-1) particles and thidiazuron (TDZ: 50, 75 and 100 lM) and their combinations on variations of growth indices, contents of plastid pigments, antioxidant enzymes, viz., superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) activities, accumulation of hydrogen peroxide (H2O2) and production of essential oils (EOs) and its major constituents in P. graveolens. Results showed that plant growth parameters increased with increasing concentrations of both TDZ (up to 75 lM) and NS (up to 40 mg l-1). Combined treatments of TDZ and NS at all employed concentrations were better in improving growth indices and pigments content, except when applied at 100 lM TDZ ? 80 mg l-1 NS. Application of TDZ75 ?NS40 significantly reduced H2O2 content by 61.2 % than control. The highest specific activity of SOD and POX were observed at TDZ50 ? NS40 and TDZ75 ? NS40 treatments, respectively. In contrast, CAT activity was strongly increased both by TDZ50 and TDZ75 ? NS80 treatments. The major EOs constituents were identified as citronellol (C), geraniol (G), cirtonellyl formate, iso-menthone, linalool and E-caryophyllene. EOs of P. graveolens plant under combined treatment of TDZ75 ? NS40 possessed C/G ratio equivalent to one, indicating EOs with the best scent quality.
