The objective of this study was to elucidate the effect of light-emitting diode treatment on early growth and inorganic elements in leaf lettuce (Lactuca sativa L. 'Oak Leaf'). In changes to leaf morphology, shoot elongation and hypocotyl length showed poor growth under red light irradiation, while red+blue light irradiation induced shorter plant height and more leaves, resulting in increased fresh weight. With respect to Hunter's color and SPAD values, lettuce seedlings grown under red+ blue and fluorescent light irradiation had a higher a* value but showed no other changes to SPAD values. Interestingly, redness in relative chlorophyll content was 1.4 times higher under red+blue light irradiation. Inorganic element (N, Ca, Mg, and Fe) and ascorbic acid concentrations increased in lettuce plants grown under LED light irradiation compared to those of lettuce grown under fluorescent light, which showed a higher P content. In conclusion, red+blue light irradiation, which stimulates growth and higher nutrient uptake in leaf lettuce, could be employed in containers equipped with LEDs.

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