Effect of light-emitting diodes (LEDs) on growth of sweet basil (Ocimum basilicum) in an aquaponics system

There is considerable interest in combining light emitting diodes (LEDs) with aquaponics for efficient plant growth. Compared with other light sources, LED lights consume less energy, operate at a low temperature, have a long shelf-life and are adjustable for intensity. In this study we produced sweet basil (Ocimum basilicum) plants in a vertical aquaponics system with laterite and soilless media, using nutrient rich manure from tilapia fish, with the aim of different light intensity and color ratio based on the growth, quality, photosynthesis and bioactivity of the plants. Twelve LEDs light treatment were tested: 1) white, as a control; 2) blue; 3) red; 4) green; 5) far-red; 6) red:white (1:1); 7) red:white (2:1); 8) red:white (3:1); 9) red:blue (3:1); 10) red:blue (5:1); 11) red:white:blue (1:1:1); and 12) red:white:blue (3:1:1). Under this plant factory environment, we found significant effects of diverse light treatments on the growth and quality of sweet basil plants. Sweet basil plants grown under red:white light (2:1) had the highest plant height and diameter, leaf length, leaf number, leaf width, photosynthetic (QY_max) and SPAD value. While red:white:blue light (3:1:1) and white stimulated higher fresh and dry weight of stem and roots. In addition, we found that red:white light (2:1), red:white:blue light (1:1:1 and 3:1:1) resulted in higher phenolic content and more fresh root growth. The combination of red:white LEDs light (2:1) was found to be the most suitable light environment for maximum growth and high quality of commercial sweet basil produced in a vertical aquaponic plant factory.