Masters Theses

Date of Award

5-2018

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant Sciences

Major Professor

Carl E. Sams

Committee Members

Fred L. Allen, Dennis E. Deyton, Dean A. Kopsell

Abstract

The use of light-emitting diodes (LEDs) in commercial greenhouse production is rapidly increasing due to technological advancements, increased spectral control, and improved energy efficiency. Research is needed to determine the value and efficacy of LEDs when compared to traditional lighting systems. The primary objective of this project was to establish the impact of narrow bandwidth blue(B)/red(R) LED lighting ratios on flavor volatiles in hydroponic basil (Ocimum basilicum var. ‘Genovese’) in comparison to non-supplemented natural light controls and traditional high-pressure sodium (HPS) lighting. Emphasis was placed on evaluating the efficacy of LED/HPS lighting sources and their impact on biomass, nutrient uptake, and flavor volatile concentrations in basil. Specific ratios of narrow-band B/R (447 nm/627 nm) LED light were used in addition to incremental daily light integrals (DLIs) to determine the impact of spectral quality and light intensity on primary and secondary metabolism of basil. Edible biomass and nutrient uptake were significantly impacted by supplemental lighting treatments and growing season. The 20B/80R LED treatment had the greatest total fresh biomass (FM) and dry biomass (DM) accumulation. Mineral analyses showed that both macro and micronutrient accumulations were impacted with supplemental lighting and across growing seasons. Many flavor volatiles varied across light treatments and showed a non-linear relationship with increasing B/R LED ratios, with the highest concentrations observed in LED ratios ranging from 20B/80R to 50B/50R. However, the concentrations of some compounds, such as methyl eugenol, were 3-4x higher in the control treatments, and decreased significantly for basil grown under supplemental lighting treatments. Every compound evaluated showed significant differences across lighting treatments and growing seasons. The results of this study show that supplemental narrow-wavelength light treatments from LED sources may be used to manipulate plant development and secondary metabolism. In addition, spectral quality and DLI have significant impacts on biomass accumulation, nutrient uptake, and flavor volatile composition in basil. The application of LED lighting to supplement natural DLI has great potential for improving overall flavor quality for high-value specialty herbs.

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