Doctoral Dissertations

Orcid ID

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Plant, Soil and Environmental Sciences

Major Professor

Carl Sams

Committee Members

Dennis Deyton, John Munafo, Curtis Luckett


This dissertation explores the influence of spectral quality from supplemental lighting and seasonal changes on primary and secondary metabolism in hydroponically grown greenhouse basil. It aims to enhance understanding of plant/light interactions and provide practical insights for light emitting diode (LED) manufacturers and commercial growers. The research is premised on the hypothesis that altering spectral quality can significantly impact primary and secondary metabolism, potentially improving flavor and increasing phytonutrients with health benefits. This project involved four phases, each building on the results of the previous ones. In Phase 1, different basil varieties were evaluated to determine aroma volatile profiles and concentrations of key secondary metabolites. In Phase 2, discrete narrow-band blue/red (B/R) wavelengths were used to investigate their impact on aroma volatile concentrations and secondary metabolic resource partitioning in basil, revealing the influence of both seasonal and supplemental lighting effects on plant metabolism. Phase 3 explored the impacts of full spectrum white LEDs and high pressure sodium (HPS) on yield and nutrient accumulation, comparing these to the optimal narrowband B/R identified in Phase 2. The final phase connected all phases, comparing the best narrowband and full spectrum treatments to a traditional HPS treatment and natural light control. These treatments were tested across various parameters, with photosynthesis and primary metabolic data recorded, yields and biometric data taken, aroma compound concentrations, and other secondary metabolic data collected. A sensory panel was conducted, and mRNA sequencing performed to determine differences in metabolic pathway expression based on lighting treatment. Analytical data from the different light treatments, sensory panel, and mRNA data were evaluated to determine which lighting regime had the most positive impact on plant physiology and biochemistry. Variation in spectral quality across seasons influences primary and secondary metabolism, in addition to the spectral qualities of different types of supplemental lighting treatments. This holistic, interdisciplinary approach revealed a light treatment that balances yield, nutrient content, and flavor preference, providing a superior product highly preferred by consumers. The research presented in this document significantly expands our understanding of the complex interplay between light conditions and plant physiology, with implications for improving crop yield and quality in controlled environment agriculture.

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