Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Biological Engineering

Committee Chair(s)

David W. Britt


David W. Britt


Astrid R. Jacobson


Joan E. McLean


Ronald Sims


Yu Huang


Changes in climate and shifting patterns of drought threaten the growth of important cash crops like wheat. The element silicon serves as a plant nutrient and shows promise for strengthening wheat against drought while remaining safe to both the crop and the positive bacteria that grow on its roots. Silicon can be added to wheat in the form of silicon-dioxide nanoparticles featuring protective coatings made from plant-beneficial nutrients. These nanoparticles can be engineered with high surface area or porous structures allowing them to be loaded with additional nutrients that can be delivered to crops. In a laboratory setting, such nanoparticles were found to adhere to wheat roots after more than 21 d growth in sand, implying direct and lasting delivery of silicon to the roots.

A small, plant-beneficial molecule, glycine betaine, is produced by wheat and other crops as a natural defense mechanism against drought and salt stress, making it a desirable nanocarrier payload for reducing detrimental side effects. Glycine betaine is reported to improve protein stability and photosynthesis in wheat, and these effects are known to increase in the presence of a surfactant. Pluronic F68 is an effective nanoparticle-stabilizing surfactant coating that can help encapsulate glycine betaine within silicon-dioxide nanoparticles and aid both glycine betaine and elemental silicon in reaching crops when added to the field. Here, Pluronic F68-coated silicon-dioxide nanocarriers are explored for enhancing glycine betaine delivery to wheat and the beneficial wheat-root bacterium, Pseudomonas chlororaphis O6. A green synthesis for Pluronic F68-coated silicon-dioxide nanoparticles is demonstrated for field-recommended doses of silicon and concentrations of Pluronic F68 that improve wheat growth by 9-12% within 5 weeks. The nanocarriers and all their components are nontoxic to wheat and the wheat-root microbiome for the tested concentrations. They were shown to effectively incorporate into wheat root epidermal cells and translocate into wheat shoots and trichomes. Glycine betaine, but not Pluronic-F68 is consumed by Pseudomonas chlororaphis O6 without the aid of protective nanocarriers, and may ultimately benefit from nanocarrier-assisted delivery to ensure delivery to the plant.