Date of Graduation

Summer 2019


Master of Science in Biology



Committee Chair

Laszlo Kovacks


phytotoxicity, nanotoxicology, engineered nanoparticles, silver nanoparticles, Arabidopsis thaliana, RNA-seq, gene expression

Subject Categories

Biology | Genetics and Genomics


Silver nanoparticles (AgNPs) have consistently been shown to have a detrimental effect on bacteria, fungi, and plants. The interaction of AgNPs with plants has received considerable scientific attention, because it is potentially through plants that these structures can enter the food chain and bioaccumulate in humans and animals. To determine the effects of AgNPs on plants, Arabidopsis thaliana seedlings were chronically exposed to sublethal levels of AgNPs using a standardized method. To gain insight on mechanism of phytotoxicity, the seedlings were exposed to low concentrations of Ag+ (in the form of silver nitrate), AgNPs, or gold nanoparticles (AuNPs). To test if NP size influenced the response by the plant, AgNPs and AuNPs were tested at both 20 nm and 80 nm sizes. Exposure to AgNO3 altered the expression of several genes, but exposure to AuNPs did not cause any measurable changes in the Arabidopsis transcriptome. Exposure of plants with 20 nm and 80 nm AgNPs, on the other hand, caused the differential expression of 226 and 212 genes, respectively, indicative of cell wall reorganization and response to oxidative and biotic stress. The size of the AgNPs had little influence on gene expression patterns. Root length measurements were taken to quantify phytotoxicity of various NPs. While AgNO3 increased root elongation, the NPs, irrespective of metal composition and size, did not cause significant differences in root length. Taken together, my data suggest that the chemical nature of the metal core is the major determinant of AgNP phytotoxicity in chronically exposed plants.


© Natalie Lynn Smith

Open Access