Silver nanoparticle detection and accumulation in tomato (Lycopersicon esculentum)

Recent years have seen significant increases in the use of silver nanoparticles (AgNPs) in areas such as medicine and agriculture. AgNPs released into environment can be accumulated by plants, potentially affecting environmental and human health. In addition, the accumulation of silver in plant tissues can negatively affect plant vascular tissues and membrane transporters that are responsible for the transport of water and essential nutrients. In this study, Lycopersicon esculentum plants were exposed to 10, 20, or 30 mg/L of silver in bulk (Ag-0), nanoparticle (AgNPs), or ionic (AgNO3) form for 7 days in Hoagland media. Tissues were then harvested and subjected to elemental, molecular, and microscopic evaluation. The highest and lowest concentration of silver was detected in roots of plants exposed to 10-30 mg/L AgNO3 (432-471 mu g/g dw) or AgNPs (40-47 mu g/g dw), respectively. Particulate silver was detected in plants exposed to 20 nm AgNPs. The highest (52,700-58,400 particles/g) and lowest (6200-13,700 particles/g) concentrations of particles were detected in roots and leaves, respectively. The membrane transporters H+-ATPase, potassium transporter, and sulfate transporter were upregulated by 23.50%, 52.09%, and 7.6% upon exposure to all forms of silver as compared to the control group. Exposure to all forms of silver resulted in larger xylem cells (70 +/- 1.1 mu m in AgNP-exposed plants) than the control group (46 mu m +/- 0.6). Collectively, the data suggest that exposure to AgNPs resulted in the translocation and accumulation of both ionic and particulate forms of silver in tomato plants, affected the structure of vascular tissues, and significantly impacted the expression of membrane transporters. These changes subsequently affect the electrochemical potential of plant cells, the balance of water and nutrient dynamics, and plant growth; all of which have implications for sustainable agriculture and ultimately human health. These results also improve our understanding of the fate and effects of nanomaterials in food crops.