Effects of irradiation quantities of mixed red and blue LEDs on the growth, total flavonoids and phenolic compound contents of leaf lettuce grown in plant factory

This experiment was carried out to investigate the effects of irradiation quantities of red and blue light emitting diodes (LED) on growth and functionality in leaf lettuce (Lactuca sativa) grown in a plant factory during 2013. The tested cultivar was 'Cheongchima (Nongwoobio. Co. Korea)'. The applied treatments were mixed red and blue LED irradiation quantities: 90/30, 80/40, 70/50, and 60/601.unol m(-2) s(-1). Air temperature and day length were 22 C and 12 h, respectively. Leaf weight was high in the 80/40 and 90/30 Imo' m-2 s-1 treatments (47.5 and 46.6 g plant-1, respectively). There were statistically significant differences in the number of leaves and leaf width among the treatments. Leaf length was longer in the 90/30 and 80/40 mol m(-2) s(-1) treatments than that of the 70/50 and 60/60 mol m(-2) s(-1) treatments. Leaf thickness was increased with increasing blue light quantity. Total flavonoids content of 'Cheongchima lettuce' was higher in the 80/40 and 60/60 mol m-z s-1 treatments (0.72 catechin mg g(-1) FW). Total phenolic compound content was higher in the 80/40 mol m(-2) s(-1) treatment (0.76 GAE mg g(-1) FW). Summarizing, a gain in leaf weight and yield of total flavonoids and phenolic compound contents was obtained in the 80/40 mol m(-2) s(-1) treatment (comprehensive results). These results may contribute to the dissemination of the plant factory growing system and production of functional lettuces.