Silver nanoparticles and silver ions: Oxidative stress responses and toxicity in potato (Solanum tuberosum L) grown in vitro

Under in vitro conditions, we examined the effects of silver nanoparticles (AgNPs) and silver (Ag) ions on potato (Solanum tuberosum L.) in terms of silver accumulation, production of reactive oxygen species (ROS), oxidative stress responses, and antioxidative defense systems. At all concentrations (except at 2 mgaEuro cent L-1), the amount of Ag in the shoots and roots of Ag ion-treated plantlets was significantly higher than in plantlets treated with AgNPs. In both treatments, total ROS and superoxide anions were increased at concentrations greater than 2 mgaEuro cent L-1. Damage caused by oxidative stress, such as ion leakage and cell death, was significantly higher in plantlets treated with AgNPs than those treated with Ag ions. Significant increases in the activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase (GR),were found in both AgNP-treated, and Ag ion-treated plantlets compared to the control. However, in AgNP-treated plantlets, GR activity was significantly decreased at 20 mgaEuro cent L-1. A significant reduction in glutathione (GSH), ascorbate (ASA), and the ratios of GSH to oxidized glutathione (GSSG) and ASA to oxidized ascorbate (DHA)were observed in plantlets treated with both AgNPs and Ag ions at concentrations higher than 2 mgaEuro cent L-1. Moreover, a greater decrease in GSH and ASA contents was seen in plantlets treated with AgNPs compared to those treated with Ag ions. The present study indicates that both AgNPs and Ag ion treatments impose oxidative stress on potato plantlets under in vitro conditions. Furthermore, based on plantlets' responses to oxidative damage, the observed alteration in the activities of radical scavenging enzymes and the depletion of GSH and ASA, AgNPs seem to have higher toxicity than the equivalent mass of Ag ions.