Can we put photobiology to work? Using supplemental light to manipulate the nutritional and sensory properties of greenhouse tomatoes
While generally viewed within the context of plant growth and development, different qualities of light are also powerful elicitors of secondary metabolic pathways in plants that affect the nutritional value and flavor of edible tissues. Leveraging fundamental photobiology principles, our studies sought to use different qualities of supplemental light including ultraviolet-B (UV-B), UV-A, blue, red, and far-red as an environmental treatment to restore garden-grown flavor and nutritional attributes to greenhouse-grown tomatoes (Solanum lycopersicum); a commercially important crop that has a poor reputation compared to its garden-grown counterparts. To test our hypotheses, we used a battery of physicochemical analyses that included total soluble solids, citric/ascorbic acid content, pH, and electrical conductivity of tomato fruits. Additionally, phenolic compounds in fruit tissues were quantified broadly using the Folin-Ciocalteu method and specific flavonoids were quantified with a more targeted approach using HPLC-ESI (-)-MS. Lycopene and β-carotene were quantified spectrophotometrically. In one study, qPCR was used to quantify genes involved in light-signal transduction in order to better understand the molecular underpinnings of plant UV-B perception. Two studies included consumer sensory panels to assess the impact of supplemental light quality on the flavor and overall perceived quality of tomato fruits, as many compounds related to flavor perception are derived from the same pathways as carotenoids and flavonoids. Our data indicate that blue, red, and far-red light had little impact on secondary metabolic processes in greenhouse-grown tomato fruits. UV-B, a wavelength of radiation blocked by greenhouse glass and a driver of flavonoid production, had a slight impact on nutritionally-relevant flavonols. However, UV-A most strongly impacted the sensory quality of greenhouse tomato fruits by increasing aroma and overall perception scores, offering a novel way to enhance the flavor of tomatoes using these qualities of light. Overall, the wavelengths of light used in these studies did not affect plant metabolism as markedly as was predicted. More research is needed to better understand how plants react to supplemental lighting while growing in a highly dynamic light environment such as a greenhouse.
Mitchell, Purdue University.
Food Science|Horticulture|Plant sciences
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