S08 - Session P4 - The effect to anthocyanin contents and its related gene expression of red leaf lettuce by irradiating blue light under vertical farm condition

Authors: Konosuke Kijima *, Kazuma Sakai, Yuji Yamada, Takashi Ikeda

At production of red color leaf lettuce varieties in a vertical farm, it is almost not turn red under white LED light condition. There are many trials that applying blue light for coloring red for red leaf lettuce varieties. However, sometimes leaves were not completely turning red, and remains green part. It is well known that the pigment in red color leaf lettuce is anthocyanin. In this study, we investigated the effect of blue light irradiation to red color leaf lettuce varieties under a vertical farm condition. Also, we analyzed anthocyanin contents and the expression of anthocyanin related genes. We grew red color leaf lettuce ( Lactuca sativa L. var. crispa ) hydroponically in a vertical farm. The growth condition was 25 o C for room temperature and using EC 1.6mS m -1 for liquid fertilizer condition. As control, we used white LEDs at 350μmol m -2 in average. We applied blue light by using blue LEDs as similar light intensity as control (Blue light regime). At 10 -30 days after sowing, after we cultivated and measured fresh weight of each plant, we cut the leaves at green or red part of the plants at blue light regime, then we proceeded anthocyanin analysis. Anthocyanin contents were measured by using HPLC. Also, we analyzed the expression levels of anthocyanin biosynthesisn related genes and also, its transcription factors. In the result, the anthocyanin content was dramatically increased at the red part of the leaf of blue light regime. Also, relative expressions of the genes were high for that part. However, when we harvested the lettuce at early stage (10 days after sowing), almost all the part of leaves were coloring at blue light regime. The plants at 30 days after sowing were not turned red completely, then the relative expressions of anthocyanin synthetic related genes were become low. We demonstrated that the relationship between coloring of red color leaf lettuce and pigment content and its related gene expression. We have to have further study that the mechanisms of coloring of it under vertical farm condition.