Determination of carbon nanotubes effects on plant phenotype, plant physiology and bollworm development

Engineered nanomaterials are man-made materials that range in size from 1-100 nm and are currently being used in various applications such as electronics, combustion, agriculture, medicine and pharmaceuticals. Carbon nanotubes (CNTs) are engineered nanomaterials with unique physical, electrical and chemical properties. CNTs are emitted into the environment through combustion, waste water treatment, medical and pharmaceutical devices, and various other waste streams, making them an important toxicant to study. Several studies have observed the uptake and effects of CNTs in plants. The effects on growth and physiology have differed depending on the plant species and type of CNT. This dissertation aimed to address the possible effects CNTs might have on plant phenotype and physiology. Two crop species were chosen for this project, tomato, because it has a known genome, and cotton, because it is economically important to Texas.
This dissertation 1) evaluated effects on the phenotype and physiology of cotton and tomato after exposure to CNTs and water-deficit, 2) examined phenotype and physiological changes, through growth, reproduction, amino acids, and plant hormones, in plants that may occur after exposure to different types of CNTs (functionalized and non-functionalized), and 3) observed effects CNTs might have on the development of cotton bollworms after ingesting CNT contaminated feed. Tomatoes grown in CNT-contaminated soil exhibited delayed early growth and maintained higher net photosynthesis under water-deficit stress compared to non-treated controls. In contrast, cotton grown in CNT- contaminated soil had increased seedling growth and flowering time but decreased net photosynthesis under water-deficit stress compared to non-treated controls. Multi-walled CNTs (both functionalized and non-functionalized) decreased early growth, delayed flowering time and increased amino acid content suggesting these types of CNTs might elicit a stress like response in plants. Plants exposed to single-walled CNTs (non-functionalized) had a higher content of phytohormones and amino acids suggesting that these CNTS may also be eliciting a stress response. Bollworm development was unaffected up to 1000 mg/kg CNTs. Although, these results are important, no robust trend in response to CNT type was observed in both plants and bollworms. Results of this study will lead to a better understanding of the fate and toxicity of CNTs in terrestrial ecosystems as well as the potential for CNTs to enter the food chain, which may pose a human health risk. This study also evaluated how plants exposed to a toxicant, such as CNTs, might respond differently to abiotic stress, such as drought. These results will lead to a better understanding of CNT and ENM influence on plant phenotype and physiology in a changing environment.