Effects of Supplemental LED Lighting based on Solar Irradiation and Carbon Dioxide Enrichment on Photosynthesis, Growth, and Yield of Greenhouse-Grown Tomato Plants

Background and objective: In recent, the productivity of greenhouse-grown tomato plants (Solanum lycopersicum) in Korea is approximately 120 kg/m2, which is just 51% of the productivity of the same plants in the Netherlands (231 kg/m2). Supplemental lighting and carbon dioxide (CO2) fertilization are considered effective strategies for improving productivity during the low-temperature season. However, few studies have analyzed the combined or independent effects of supplemental LED lighting and CO2 enrichment on the productivity of greenhouse-grown tomato plants. This study aims to evaluate the effects of supplemental LED lighting and CO2 enrichment on the photosynthesis, growth, and yield of tomatoes cultivated in a plastic greenhouse.Methods: The experiment was conducted using the tomato cultivar "Dafnis," grown in a coir medium in a plastic greenhouse at the National Mokpo University-affiliated farm. Supplemental lighting with LEDs was set to maintain 100 μmol⋅m-2⋅s-1 when daily accumulated light levels were insufficient. CO2 enrichment, using liquid CO2 gas rated for food and beverage use, was targeted at 600 μmol⋅mol-1 to enhance photosynthetic efficiency. Photosynthetic parameters (Vcmax, Jmax, Rd) were measured using a photosynthesis meter and the FvCB model. Growth traits, including hypocotyl length, leaf number, and fresh weight, were recorded at 2-week intervals. Yield data were collected cumulatively (kg/10a).Results: Photosynthetic rates, Jmax, and Rd showed no significant differences, but Vcmax was 15.24 µmol⋅m-2⋅s-1 higher in the Combined Treatment group than in the Control group (Control group: 66.98 µmol⋅m-2⋅s-1; Combined Treatment group: 82.22 µmol⋅m-2⋅s-1 ). Cumulative yields (kg/10a) were as follows: 9,341 for the Control group, 11,852 (+15%) for the CO2 Enrichment group, 10,951 (+22%) for the Supplemental Lighting group, and 13,116 (+29%) for the Combined Treatment group.Conclusion: Although no significant differences were observed in photosynthesis or shoot growth except for Vcmax, the combined application of supplemental lighting and CO2 enrichment significantly improved tomato yields. This suggests the potential to enhance the productivity of greenhouse-grown tomato plants in low-temperature conditions.