2017 Volume 55 Issue 2 Pages 85-91
Several studies have reported that the circadian rhythm of leaf lettuce (Lactuca sativa L.) is approximately 24 h and that the fresh weight of Greenwave, a cultivar of leaf lettuce, is larger under the light-dark period of 22 h or 24 h. In this study, we investigated the optimal light-dark cycles for Greenwave and the deciding factors of optimal light-dark cycles by cultivation experiments under several light-dark conditions in plant factory. By optimization of light-dark cycles, we obtained the optimal light-dark conditions for the light/dark ratio (L/D) of L/D=2 and the light-dark period of 15-22 h (T15-T22). In addition, the higher growth rate on T21 and T22 conditions was suggested to be related to the decrease in leaf starch concentration at night. The results in this study suggests that the cultivation of leaf lettuce under light-dark conditions reduce running costs in plant factory with artificial lighting (PFAL).
