Growth Characteristics of Tomato Seedlings Irradiated by White and Far-red LED lights in Vertical Farms

For stable year-round seedling production of Solanum lycopersicum, this study was conducted to select the appropriate light source and light intensity in a vertical farm.The seedlings were cultivated with a 14-hour light period at an air temperature of 25/20.The effects of four light-emitting diodes (LEDs)-cool white LED and warm white LED, both with and without far-red LED light-were tested at a photosynthetic photon flux density of 350 molm -2 s -1 .Growth characteristics, such as plant height and fresh weight, showed no significant differences between the cool white LED and the warm white LED.However, the addition of far-red light significantly increased plant height, internode length, stem diameter, leaf area, and fresh weight while decreasing SPAD values.Seedling qualities such as compactness improved with cool white LED without far-red light.In a second experiment, the red/far-red ratio was adjusted between 1.4 and 15.2 using cool white LED.As the ratio of far-red light increased, overall growth improved, but compactness was higher at red/far-red ratios of 2.5 and 3.6.Under various light intensities at a red/far-red ratio of 2.5, a light intensity of 300 molm -2 s -1 or higher showed higher compactness.Therefore, for tomato seedling production in a vertical farm using artificial light, cool white LED with far-red light at an R/FR ratio of 2.5 to 3.6 and a light intensity of 300 molm -2 s -1 was found to be effective.