Does plant growing condition affects biodistribution and biological effects of silver nanoparticles?

Among the many different types, silver nanoparticles (AgNPs) are the most commercialized and applied engineered nanoparticles in a wide range of areas, including agriculture. Despite numerous studies on their safety and toxicity of AgNPs, data on their effect and interactions with terrestrial plants are largely unknown. This study aimed to investigate the effect of growing conditions on the response of pepper plants (Capsicum annuum L.) to citrate-coated AgNPs. Growth parameters, biodistribution, and defence response were examined in peppers grown hydroponically or in soil substrate. In addition, the effects of nano and ionic form of silver were compared. The leaves and stems of peppers grown in substrate showed a higher bioaccumulation compared to hydroponically cultivated plants. The nano form of silver accumulated to a higher extent than ionic form in both leaves and stems. Both silver forms inhibited pepper growth to a very similar extent either through hydroponic or substrate growing settings. Unlike other studies, which investigated the effects of unrealistically high doses of AgNPs on different plant species, this study revealed that vascular plants are also susceptible to very low doses of AgNPs. Both silver forms affected all parameters used to evaluate oxidative stress response in pepper leaves; plant pigment and total phenolics contents were decreased, while lipid peroxidation and hydrogen peroxide lever were increased in treated plants. Similar biological effects of both nano and ionic Ag forms were observed for both substrate and hydroponic growing systems.