Date of Award

5-1-2015

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Ma, Xingmao

Abstract

Rapid advancement of nanotechnology has caused serious concerns about the potential release and accumulation of engineered nanoparticles (ENPs) in the environment. As the most popular ENP in commercial products, the phytotoxicity of AgNPs has been extensively investigated. While it is now generally agreed that AgNP itself exerts unique toxicity to plants in addition to that of dissolved silver ion, the accumulation and fate of different forms of silver in plant tissues are unknown. The first part of this study investigated the phytotoxicity, accumulation and transport of Ag with different physical and chemical characteristics (e.g. ionic, nanoparticles, and bulk) in two agricultural crop species: Glycine max (soybean) and Triticum aestivum (wheat). The results showed that different forms of Ag demonstrated differential toxicity to these two species, with the Ag+ at the same nominal concentration displaying the strongest effect on plant growth. Exposure to 5 mg/L of elemental Ag in different forms all resulted in significant deposition on the root surface but its morphology and distribution patterns varied considerably. Internalization was observed for all forms of Ag. However, when Ag enters into plant roots, the upward transport efficiency from roots to shoots varied with both Ag type and plant species. In addition to AgNPs, gold nanoparticles (AuNPs) has also attracted significant attention due to their broad applications. However, most previous toxicity studies have been heavily geared towards animal and human cell lines, with limited information available for the AuNP plant interactions. The second part of this study concentrated on elucidating the impact of surface coating on the phytotoxicity and plant uptake of AuNPs by Phaseolus vulgarisi (bush bean). The results showed that the impact of 5 mg/L of AuNPs on several physiological processes of plants was insignificant, regardless of the surface coating materials. However, AuNPs with different surface properties displayed significant differences in some biochemical parameters including the concentrations of hydrogen peroxide in plant roots and the activities of some enzymatic antioxidants. Similar to AgNPs, deposition of AuNPs on plant root surface was observed for all coatings. Surface coatings also affected the internalization of AuNPs in plant root cells and their subcellular localization. Overall, the study demonstrated that the physical and chemical properties of Ag and Au NPs play important roles in their interactions with plants and consideration of the unique properties of nanoparticles is critical in assessing their food safety concerns.

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