Date of Award

2014-01-01

Degree Name

Doctor of Philosophy

Department

Chemistry

Advisor(s)

Jorge L. Gardea-Torresdey

Abstract

The profuse use of nanoparticles (NPs) in consumer products has raised concerns about their impacts in environmental and human health and possible transfer into the food chain through plants. Cucumber (Cucumis sativus L.) is a widely cultivated garden vegetable that could be in contact with NPs through biosolids. In this Dissertation research, the impact of TiO2 NPs was evaluated in cucumber plants grown in hydroponics and sandy loam soil. Hydroponically grown plants were treated for 15 days with 0-4000 mg/L of TiO2 NPs, and their vegetative tissues were studied using synchrotron micro X-Ray Fluorescence (micro-XRF) and Micro X-ray Absorption Near Edge Structure (micro-XANES). In soil, the cucumber seeds were germinated and grown to full maturity with 0-750 mg/kg of TiO2 NPs. At harvest, vegetative tissue and fruits were analyzed using synchrotron micro-XRF, micro-XANES spectroscopic techniques, and biochemical assays. Fourier transform infrared (FTIR) spectroscopy was used to determine possible changes in macromolecules of cucumber fruit. Results from hydroponic experiments showed that TiO2 significantly increased root length at all concentrations (average >300%). In addition, micro-XRF analysis showed that the Ti was taken up from the hydroponic solution and transported through the xylem from the root to leaf tissue, including to trichomes. The micro-XANES spectra showed that Ti found in the vascular system of cucumber was present as TiO2, demonstrating that TiO2 NPs were not biotransformed. Results from soil experiments showed a significant increase in catalase activity at all NP concentrations; while ascorbate peroxidase decreased at 500 mg kg-1 in cucumber leaves. In addition, leaves from 750 mg kg -1 TiO2 NPs treatment, showed an increase in total chlorophyll content. FTIR spectra of fruits from TiO2 NP treated plants showed significant differences in all band areas, suggesting modification in macromolecules of cucumber fruits. Furthermore, micro-XRF and micro-XANES results showed that TiO2 NPs were translocated from roots to fruit without biotransformation or crystal modification, suggesting that TiO2 NPs could be introduced into the food chain with unknown consequences for human health. To our knowledge, this is the first report on the presence and effects of TiO2 in the edible portion of cucumber plant grown in soil with TiO2 NPs.

Language

en

Provenance

Received from ProQuest

File Size

65 pages

File Format

application/pdf

Rights Holder

Alia D. Servin

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