Effect of Different Light Spectra on Growth and Morphology of Lettuce in Plant Factory System

In recent decades, production of crops in plant factory vertical systems attracted lots of attention since it makes possible crop production with optimum consumption of resources, irrespective of climate conditions. In the present study, growth and yield of the lettuce (Lactuca sativa L.) in the plant factory vertical system under artificial light were investigated. To do so, the plants were grown in a hydroponic system using nutrition film Technique (NFT). Completely randomized design was used to study the impact of different light spectra using light emitting diodes (LED), modules including red and blue (RB) lights with different ratios (RB,90:10 – RB, 80:20 – RB, 70:30), red, blue, and far red (RBFr in 3:1:1 ratio), and red and white (RW in 1:1 ratio). Lighting period was set to 18 h at an intensity of 250 μ.mol m-2 s-1. The highest leaf area and plant weight, as the main yield characteristics of lettuce, were detected under RB 80:20 treatments. The plants grown under RBFA showed shade avoidance responses (tall plants with low leaf area), which is not favourable for lettuce production. In conclusion, due to having the best growth and yield under RB 80:20 light spectra, it is introduced as the best light spectrum for production of lettuce plants in plant factory system.