The Effects of Low Concentrations of Silver Nanoparticles on Wheat Growth, Seed Quality, and Soil Microbial Communities

The growing demand for and production of commercial silver nanoparticles (AgNPs) inevitably increases the risk for their environmental release and soil accumulation, which could have deleterious effects on plant growth and soil microorganism communities. However, to date, little is known about how AgNPs impact plant growth, seed quality, and soil microbial communities. We therefore evaluated wheat growth and seed quality after exposure to low concentration of AgNPs while characterizing the composition of the associated soil microbial community by high-throughput sequencing of 16S rRNA genes. Our results showed that low concentration of AgNPs (1 mg/kg in fresh soil) neither inhibited wheat seedling growth nor changed the amino acid content in wheat seeds. Interestingly, the soil microorganisms in the wheat-planted group had more diversity and richness than those in the bulk-soil group. The structure of the bacterial community was affected by AgNP exposure, most significantly during the transition from the seedling to the vegetative stage of the wheat, but recovered to normal level after 49 days of treatment. In conclusion, the results from this study highlight that the environmental risks associated with low concentration of AgNPs, which have clear bioeffects on soil microorganisms, warrant further investigation.