Growth and Antioxidants of Cherry Tomato Seedlings Grown under Monochromatic Light-emitting Diodes

Individual light spectrum within visible light spectra plays an important role in plant growth and development. Light-emitting diodes (LEDs) of a short wavelength range can be used in closed-type transplants production systems as an artificial light source. This study aimed to determine the effects of monochromatic LED on growth and antioxidants of cherry tomato seedlings (Lycopersicon esculentum Mill. cv. ‘Cuty’). Two-week-old cherry tomato seedlings germinated under normal growing conditions (24 °C, fluorescent lamp + high pressure sodium lamp, a photosynthetic photon flux (PPF) of 112.9 ± 5 µmol·m^-2·s^-1, 12 hours photoperiod) were transplanted in a growth chamber equipped with various monochromatic LEDs (blue LED, 456 nm; green LED, 518 nm; red LED, 654 nm; white LED, 456 nm + 558 nm) and fluorescent lamp (control) and cultivated at 27/18°C (day/night) with a PPF of 205 ± 5 µmol·m^-2·s^-1 and 12 hours photoperiod for 4 weeks. The plant height, stem length, and internode length of tomato seedlings subjected to blue LED were the highest among treatments during whole growth stage. Blue LED induced about 1.5–2.2 times higher stem length than red and white LED. The fresh weights of shoots and roots in red and green LEDs were higher than the other treatments including control after 4 weeks of LED treatment. The chlorophyll content (SPAD value) of blue LED was significantly lower than the other LED treatments. In contrast, blue LED stimulated the biosynthesis of antioxidants in the tomato seedlings. Antioxidant capacity of blue LED was 2.1 times higher than that of green LED. Thus, this study suggested that the manipulation of light quality using LEDs is a critical factor for growth and antioxidants of cherry tomato seedlings.