Genotoxic and Physiological Responses to Repeated Exposure to Low-Concentration Silver Nanoparticles in Vicia faba Through Root and Foliar Uptake Pathways.

Silver nanoparticles (AgNPs) are among the most widely used engineered nanomaterials, increasing the likelihood of repeated plant exposure through soil, water, and atmospheric deposition. However, the biological consequences of repeated exposure through different uptake pathways remain insufficiently understood. This study characterized citrate-reduced AgNPs and evaluated their genotoxic and physiological effects in Vicia faba following repeated root and foliar exposure. Physicochemical characterization included SEM, energy-dispersive X-Ray spectroscopy, dynamic light scattering, zeta potential analysis, and UV-Visible spectroscopy. Cytogenetic damage was assessed using the mitotic index, micronucleus test, chromosomal and nuclear abnormalities, and alkaline comet assay, while chlorophyll content and stem growth were determined as physiological endpoints. The synthesized AgNPs were predominantly spherical, exhibited colloidal stability, and produced greater biological effects than bulk silver. Repeated exposure reduced cell proliferation and increased micronuclei, chromosomal aberrations, nuclear buds, binucleated cells, and DNA damage in both roots and leaves. Root tissues consistently showed greater DNA damage following AgNP exposure, while AgNPs also caused greater reductions in chlorophyll content and plant growth than bulk silver. These findings demonstrate that repeated AgNP exposure induces tissue-specific and persistent biological responses, emphasizing the importance of incorporating repeated-exposure scenarios and multiple uptake pathways into environmental risk assessments of engineered nanomaterials.