No Differences Seen Between Supplemental LED, HPS Lighting in Tomato Growth

A feasibility study has shown that using LEDs as greenhouse grow-lights for tomato crops does not diminish fruit quality, suggesting a potential alternative for or supplement to high-pressure sodium (HPS) lights.

While favored for their energy-saving potential, LEDs have not been studied thoroughly for their effects on fruit quality, specifically that of tomatoes, according to researchers from Purdue University. The researchers conducted three separate studies to investigate the effect of supplemental light quantity and quality on greenhouse-grown tomatoes.

Tomato plants received supplemental lighting from high-pressure sodium lamps or from intracanopy LED towers. Results showed that tomato quality was largely unaffected by the type of light treatment. Courtesy of Michael Dzakovich.

Plants were grown either with natural solar radiation only (control group), natural solar radiation plus supplemental lighting from HPS lamps, or natural solar radiation plus supplemental light from intracanopy (IC) LED towers.

The scientists analyzed plant responses by collecting chromaticity, sugar concentration, titratable acidity, electrical conductivity and pH measurements. Contrary to their hypothesis, fruit quality was largely unaffected by direct IC supplemental lighting, the researchers said.

The study also included sensory panels in which tasters ranked tomatoes for color, acidity and sweetness using an objective scale. The tasters were also asked to rank tomato color, aroma, texture, sweetness, acidity, aftertaste, and overall approval using a five-point preference scale.

By collecting both physicochemical and sensory data, the researchers said they were able to determine whether statistically significant physicochemical parameters of tomato fruit also reflected consumer perception of fruit quality.

The sensory panels indicated that physicochemical differences were not noticeable to tasters. In fact, the researchers said, the tasters could not discern between tomatoes from different supplemental lighting treatments or those from the unsupplemented controls.

The study was published in HortScience 50 (10): 1498-1502.