Effects of Supplemental Lighting with Light-Emitting Diodes (LEDs) on Tomato Yield and Quality of Single-Truss Tomato Plants Grown at High Planting Density

In the present study, we investigated the effects of supplemental lighting (SL) with white, red, and blue light-emitting diodes (LEDs) on the yield and quality of tomato grown under the single-truss tomato production system (STTPS). SL was applied for 28 days during the rapid fruit development stage. Based on the same power consumption, the light treatments with the white and red LEDs increased the fresh yield of tomato by 12 and 14%, and the dry yield by 16 and 14%, compared with the control (without SL), respectively. Based on the unit photons emitted, the white LEDs showed high efficiency as the red LEDs in increasing tomato yield, followed by the blue ones. The results were probably due to the white LEDs that contained more than 50% of green light characterized by high penetration into the canopy. The sugar and ascorbic acid contents were not affected by SL from the LEDs. These results indicated that the white and red LEDs were effective in enhancing tomato yield and, in particular, the white LEDs with a combination of red, blue, and abundent green light would be more suitable to the use of STTPS at a high plant density.