Exploring Plant-UV Interactions with Greenhouse Tomatoes: Stress, Flavor, and Phytochemicals

Fruits harvested from off-season greenhouse tomato plants tend to be mealy, nutritionally mediocre, and bland. By contrast, tomatoes of the same varieties grown outdoors in the summer tend to have a reputation of superior fruit flavor and nutritional quality. Still, varieties that produce excellent fruit outdoors can yield mediocre fruit when grown in greenhouses. Therefore, environmental factors may be a critical mediator of fruit quality rather than genetics, per se. Presently, there is a gap in knowledge with regard to the role of UV-B radiation (280 – 320 nm) in determining greenhouse tomato quality. Since UV-B radiation is uniquely present outdoors, but largely absent within glass greenhouses, we hypothesize that  UV-B supplemental radiation will impart quality attributes typically associated only with ‘garden-grown’ tomatoes onto greenhouse tomatoes. To test this hypothesis, greenhouse tomatoes supplemented with UV-B radiation were compared with unsupplemented controls. Fruits were analyzed for basic physicochemical attributes (total soluble solids, citric/ascorbic acid content, pH, and electrical conductivity). Carotenoids, phenolics, and volatile organic compounds were quantified, providing a broad canvas of nutritional and sensory attributes. An organoleptic sensory panel complemented this study by determining the sensory relevance of various chemical differences. To further understand greenhouse tomato responses to UV-B radiation, photosynthetic efficiency, stomatal conductance, and leaf fluorescence were assessed to provide markers of physiological stress that UV-B radiation might impart to supplemented plants in the greenhouse environment. Lastly, tomato fruits grown seasonally in a nearby field plot were assessed as above to provide a chemical/sensory baseline for ‘garden-grown’ tomato fruits.