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  4. ENHANCING YIELD, NUTRITION, AND WATER-USE EFFICIENCY OF LETTUCE (Lactuca sativa) WITH GREENHOUSE LIGHT SPECTRUM AND CARBON DIOXIDE ENRICHMENT

ENHANCING YIELD, NUTRITION, AND WATER-USE EFFICIENCY OF LETTUCE (Lactuca sativa) WITH GREENHOUSE LIGHT SPECTRUM AND CARBON DIOXIDE ENRICHMENT

File(s)
Holley_cornellgrad_0058F_12932.pdf (2.44 MB)
Permanent Link(s)
https://doi.org/10.7298/zqyb-6n39
https://hdl.handle.net/1813/111717
Collections
Cornell Theses and Dissertations
Author
Holley, Jake
Abstract

Controlled Environment Agriculture (CEA) provides a means to grow fruits and vegetables year-round, regardless of local climate. This form of growing is resource intensive and requires large inputs of energy to maintain heat, lighting, and humidity. New Light-Emitting Diode lighting offers vastly superior electrical efficacy to older technologies, and supplementing carbon dioxide can lower overall lighting needs. However, relatively little is known about how these technologies impact nutritional quality of leafy greens especially in terms of xanthophylls, eye health pigments. Three experiments aimed to quantify effects of supplemental light and carbon dioxide on the growth, morphology, and nutritional content of lettuce were conducted. The objective of Chapter 1 was to quantify the growth, morphology, and nutritional difference in lettuce grown under increased concentrations of CO2. Two varieties of lettuce, ‘Rex’ and ‘Rouxai’, were grown within growth chambers with CO2 concentrations at 400, 800, 1200, and 1600 ppm. Lettuce fresh and dry mass significantly increased from by 20 to 28 percent as CO2 increased from 400 to 800ppm, but further increases in CO2 had minimal biomass gains. Violaxanthin, one type of xanthophyll, was observed to decrease in ‘Rouxai’ between 400 to 1200 ppm. However, no other nutritional compounds, such as lutein, anthocyanins, or mineral components, were significantly affected. Overall, supplementation of CO2 leads to increases in biomass production but was found to only minimally affect nutritional content suggesting CO2 enrichment is an energy efficient practice with little impact on nutritional quality. Supplemental light in greenhouses provides a means to reach daily light integral (DLI) targets when sunlight is not sufficient to maintain productive growth. Supplemental light fixtures emit different spectra depending on their technology and design, and different spectra are known to have effects on plant growth. In Chapter 2, different spectra of lights including High Pressure Sodium (HPS), Ceramic Metal Halide (CMH), narrow spectrum red and blue LEDs, and white LEDs were used as supplemental light were applied to plants to determine the impact of spectra on plant growth and nutritional quality. Further the experiment was replicated across a 6 month period with different sunlight values to determine differences of growth as different quantities of sunlight and supplemental light contributed to a fixed DLI. Few differences were observed between lighting spectra, however, increases in fresh and dry weight were positively correlated to the fraction of sunlight that contributed to the total lighting goal. Further research if the positive effect of sunlight is due to far-red, infra-red, leaf temperature, or other factors. Given contradictory scientific literature on light quality and nutrition and water use, the objective of Chapter 3 was to determine the impact of greenhouse supplemental light spectra on photosynthesis, whole-plant water use efficiency, xanthophyll and anthocyanin nutrition response of lettuce. Lighting sources include HPS, CMH, broad spectrum white LEDs and narrow spectrum R:B LEDS. High Pressure Sodium (HPS), Ceramic Metal Halide (CMH), narrow spectrum red and blue LEDs, and white LEDs were used as supplemental light source for two varieties of lettuce, ‘Rex’ and ‘Rouxai’. High Pressure Sodium lights yielded more fresh weight than 70% red and 30% blue LEDs. While HPS plants consumed more water per plant, water used per unit of fresh mass produced was lower under HPS in comparison to red and blue LEDs, making HPS more water-use efficient as a lighting source. The nutritional composition, specifically anthocyanins and xanthophylls, were highest under 70% red and 30% blue LEDs in comparison to white LEDs and HPS for anthocyanin and only HPS for xanthophylls. More work is needed to balance high plant productivity and nutritional content which are often at odds with each other. Promising future work includes dynamic plant light recipes (adjusting light spectrum during the crop stage) as well as developing spectra to emulate sunlight.

Description
131 pages
Date Issued
2022-05
Keywords
Hydroponic
•
Light-emitting diodes
•
Lighting
•
Water-use efficiency
Committee Chair
Mattson, Neil S.
Committee Member
Timmons, Michael Ben
Moraru, Carmen I.
Degree Discipline
Horticulture
Degree Name
Ph. D., Horticulture
Degree Level
Doctor of Philosophy
Type
dissertation or thesis
Link(s) to Catalog Record
https://newcatalog.library.cornell.edu/catalog/15529954

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