Quality of Norwegian tomatoes: Effects of hybrid supplemental lighting systems on sugar content in tomato fruits grown in greenhouses

Abstract

The effects of supplemental lighting on greenhouse crops have been of recent interest, especially to those countries with seasons of limited natural light. This study aims to analyze the effects of both high-pressure sodium (HPS) top lighting with intra-canopy light-emitting diodes (LED), and to find a recommended treatment for efficient growth of high-quality tomatoes in Norway. This combination lighting system is predicted to have positive effects on the sugar contents of tomato fruit, especially on glucose and fructose concentrations, thus improving tomato quality. Ion chromatography (IC), gas chromatography-mass spectrometry (GC-MS), and absorption spectroscopy were used to first determine the most effective method to analyze sugar content in this study. IC was determined to be the best fit and was further utilized to analyze glucose and fructose concentrations across seven light treatments of various HPS top lights and LEDs. The concluded recommendation to Norwegian farmers from this study is a HPS top light with flux intensity of 263 W/m2 in combination with 70 W/m2 intra-canopy LEDs.