Date of Award

2021-12-01

Degree Name

Doctor of Philosophy

Department

Environmental Science and Engineering

Advisor(s)

Jorge L. Gardea-Torresdey

Abstract

Engineering nanoparticles (ENPs) have been widely used in industry due to their promising chemical, physical, electrical, magnetic, optical, and electronic properties. Copper-based ENPs are used as gas sensors, catalysts, semiconductors and agricultural products, among others. Because of their antifungal and antibacterial properties, they are used in agriculture as insecticides, herbicides and antifungal agents. Due to their mass production and use, ENPs are likely to be ubiquitous in our in the environment in the near future. In addition, metal nanoparticles are usually coated with organic compounds to enhance the properties of the nanoparticles. Previous studies have shown that copper-based ENPs can interfere with plant physiology and development. However, to our knowledge, very little work has been done on the effects of Cu-based NPs in rice (Oryza sativa) and soybean (Glycine max) plants. Rice is a very important crop widely consumed across cultures as a source of nutrition and caloric intake. Soybean is a worldwide consumed plant, which is very rich in protein. This research project is aimed to understand the effects of copper-based compounds on rice and soybean plants at full life cycle. It also analyzes the effects of surface coated copper based nanoproducts on soybean plants. The investigation included two parts. The first part consisted of culturing two type of rice plants (cultivated and weedy) until reaching physiological maturity (120 days), in soil amended with nano CuO (nCuO), bulk CuO (bCuO), and ionic copper (CuSO4) at 0, 75, 150, 300, and 600 mg/kg. Cu translocation, essential element accumulation, yield, sugar, starch, protein content, and the expression of auxin associated genes in grains were determined. The grains of weedy and cultivated rice were differentially impacted by CuO-based compounds. At ≥ 300 mg/kg, nCuO and bCuO treated rice had no grain production. Treatment at 75 mg/kg significantly decreased grain yield as compared to control with the order: bCuO (by 88.7%) > CuSO4 (by 47.2%) ~ nCuO (by 38.3% only in cultivated rice). These findings demonstrate a cultivar-specific and concentration-dependent response of rice to nCuO. A potential use of nCuO at 75 and 150 mg/kg in cultivar-dependent delivery system was suggested based on enhanced grain nutritional quality, although the yield was compromised. The second part encompassed the evaluation of the effects that citric acid coated copper oxide nanoparticles (CuO-CA NPs) and their application process (foliar exposure, soil exposure) have on the growth and physiology of soybean (Glycine max). This part was conducted in two methods of application, soil exposure and foliar exposure. Seedlings (14-day-old) were transplanted into soil amended with 0 (control), 75, and 300 mg Cu/kg or foliar applied Cu-NPs suspensions. After nanomaterials exposure via foliar and soil application, Cu was detected in the roots, leaves, stem, pod, and seed of the plant. Cu was distributed differently depending on plant organs and surface coating. Foliar application of CuO NPs and CuO-CA NPs increased the soybean yield by 169.47% and 170.07%, respectively. In contrast, the ionic Cu treatment and soil exposure did not affect soybean yield. Our results show that CA coating changed the CuO NPs toxicity in soybean. This research provides direct evidence for the positive effects of CuO-CA NPs on soybean, including accumulation and transfer of the particles, which may have significant implications concerning the risk NPs pose to food safety and security.

Language

en

Provenance

Received from ProQuest

File Size

113 p.

File Format

application/pdf

Rights Holder

Chaoyi Deng

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