Supplemental intracanopy far-red radiation to red LED light improves fruit quality attributes of greenhouse tomatoes

Abstract

Off-season greenhouse tomatoes have a poor reputation relative to their in-season, field-grown counterparts. Previously, we reported that supplemental intracanopy far-red (700–800 nm, FR) radiation in addition to red (600–700 nm, R) light with light-emitting diodes (LEDs) significantly decreased fruit water content compared to R LEDs alone and high-pressure sodium (HPS) lamps, the most common supplemental lighting used in commercial greenhouses. We hypothesize that supplemental R + FR LEDs during production improves fruit quality attributes (i.e., physicochemical properties, mineral concentrations, and sensory properties) in greenhouse tomatoes compared to R LEDs and HPS lamps. Both intracanopy LED lights increased fruit yield and biomass compared to HPS lamps. R LEDs increased dry matter ratio and improved overall physicochemical proprieties such as total soluble solids (TSS), titratable acidity (TA), and pH; however, R + FR LEDs had more significant effects on all measured attributes than did R LEDs. Similarly, R LEDs increased potassium, magnesium, and calcium content in whole fruit by 30, 74, and 40% compared to HPS lamps, and the addition of FR to R LEDs further increased sodium (Na) content and concentration. Consumer sensory panelists rated higher for sensory attributes (aroma, sweetness, acidity, and texture) of R + FR LED-supplemented tomatoes on a hedonic scale compared to R LED-supplemented ones. Importantly, HPS lamp-supplemented tomatoes had the least desirable quality attributes even when compared at the same ripe stage as LED-supplemented ones. Energy use efficiency (EUE) was not different between R + FR LEDs and R LEDs, which was 5 times higher than that of HPS lamps. Our results demonstrate for the first time that fruit quality attributes of greenhouse tomatoes can be improved by supplemental intracanopy lighting with R + FR LEDs to a degree that consumer panelists could perceive the differences. Therefore, we conclude that supplemental R + FR LEDs is indispensable for improving fruit quality of greenhouse tomatoes during off-season production.