Tomatoes are one of the most consumed vegetables in the world. Unfortunately, obtaining a high quality tomato yield in our latitudes is inconceivable without additional lighting. Changes in biochemical composition are mainly dependent on the light received by the plant. During the winter months, natural daylight at 55 ° latitude is insufficient to provide the necessary vegetation for fruit-bearing vegetables. The aim of this study is to investigate the changes in the biochemical composition of tomato fruits by using less conventional lighting methods, which could offer potential energy savings by providing higher levels of biologically active substances in tomatoes. The study was conducted in a greenhouse of Latvia University of Life Sciences and Technologies during the winter season 2018-2019, using a 16-hour photoperiod. LED, Induction, and High Pressure Sodium Lamps (as control) were used in the study. These lighting devices, with some differences, simulate daylight. Three tomato cultivars: ‘Diamont F1’, Encor F1’and ‘Balzano F1’were studied. The study specified the tomato yield and the following biochemical parameters: soluble sugars (BRIX), vitamin C, organic acids, lycopene, carotenoids, phenols and flavonoids. As expected, the yield and species-specific pigment content of tomato fruit is largely dependent on the genetics of the variety. On the other hand, biologically active compounds such as organic acids, soluble sugars, ascorbic acid and flavonoids undergo more changes due to the composition of the light. The obtained biochemical parameters give an opportunity to consider different illumination methods and the need to carry out further studies in order to confirm the conclusions. Significantly higher yields were observed in the variant with conventionally used high pressure sodium lamps. In mean time, it should be noted that in the variant with LED lamps, higher content of lycopene as well as phenols and vitamin C were observed.
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