To meet demands of consumers for fresh tomatoes during off-seasons, greenhouse tomato growers often rely on supplemental lighting. Growers are looking for LED lighting, known for their energy-saving potential, as an alternative to high-pressure sodium lamps in greenhouse operations. A recent study by Michael Dzakovich, Celina Gómez, and Cary Mitchell from the Department of Horticulture and Landscape Architecture at Purdue University, offers latest information about the possibility of using LEDs in greenhouse tomato operations.
These researchers published the study of supplemental lighting experiments in HortScience (October 2015). They observed that LEDs could be a possible alternative to high-pressure sodium supplementation. They said, ?There is huge interest in LEDs’ potential to influence the phytochemical and flavor profile of various high-value crops. However, little fruit quality-attribute work with LEDs has been done on a long-duration.”
These researchers conducted three different studies to explore the effect of supplemental light quantity and quality on greenhouse-grown tomatoes. Tomatoes were grown either with solar radiation only, solar radiation plus supplemental lighting from high-pressure sodium lamps, or natural solar radiation plus supplemental light from intracanopy (IC) LED towers. They studied plant responses by collecting chromacity, Brix, titratable acidity, electrical conductivity, and pH measurements and said that contrary to their hypothesis, fruit quality was largely unaffected by direct, IC supplemental lighting.
It also included sensory panels in which tasters marked ranking for tomatoes, using an objective scale, for color, acidity and sweetness using an objective scale. Tasters were also asked to rank tomato color, aroma, texture, sweetness, acidity, aftertaste, and their approval using a five-point hedonic scale. “By collecting both physicochemical and sensory data, we were able to determine whether statistically significant physicochemical parameters of tomato fruit also reflected consumer sensivity of fruit quality,” the researchers said. Tasters indicated that physicochemical differences were not clear to them. They could not even distinguish between tomatoes from different supplemental lighting treatments or those from the unsupplemented controls.
According to the researchers, the study demonstrated that greenhouse tomato fruit quality was unaffected either by the type of supplemental lighting or supplemental lighting per se. Physicochemical measurements pointed out only minor variation among fruits grown under different lighting regimes, and these findings were supported by nonsignificant differences in sensory attributes. The researchers said that results are quite encouraging for tomato growers interested in reducing energy consumption in greenhouses.