Evaluation of Growth and Quality in Latuca Sativa L. under Different Photoperiods

The growth and quality of Latuca Sativa L. (Lettuce Meraviglia d'inverno) in a closed-type plant factory system with various photoperiods under the same daylight integral (DLI) were evaluated in this study. Four groups with 12 samples each were grown hydroponically under LED light sources with DLI of 4 mol/m 2 /d ± 9% at 18h/6h, 12h/12h, 11h/1h and 9h/3h light/dark periods. The light sources were generated by LEDs with the wavelengths of 660 nm (red) and 450 nm (blue) under the same light intensity. In the evaluation, any occurrence of tipburn, marginal necrosis and leaf yellowing was counted as unqualified leaf. Results showed that the group under the higher photosynthetic photon flux density (PPFD) showed the highest yield and the lowest percentage of unqualified leaves under the same DLI. Under rapid photoperiod of 9h/3h, the yield increased even the PPFD was low. Low PPFD with high light dark ratio resulted in the highest percentages of physiological disorder and the lowest fresh mass. It suggests that yield of lettuce may be further increased by combining rapid photoperiods and high PPFD for the same energy cost.