Effects of light quality during supplemental lighting on the flowering in an everbearing strawberry

The aim of this study is to examine the effect of the light quality of supplemental lighting during the night on the flowering and fruiting in an everbearing strawberry. Each plant of the everbearing strawberry (Fragaria x ananassa Duchesne 'Pechka') was transplanted into a 15-cm plastic pot in February 2016. The LED lamps were installed over the bench in a greenhouse kept by the minimum temperature 16 degrees C, and night supplemental lighting was provided just after the transplantation. Lighting time was set to 16 h from 16: 00 to 08: 00, and PPFD was set to 80 mu mol m(-2) s(-1) at the top of the plant. Three monochromatic lights were irradiated with blue, green, and red LED lamps which have a peak wavelength of 470, 530, and 640 nm, respectively. Plants under the blue LED produced the largest number of flower clusters whereas the plants under the red LED produced the fewest. The total weight of flower clusters including developed fruits plant(-1) under the blue LED reached two times more than under the red LED in June 2016 because the blue light promoted the flowering and fruiting of each floret. There are some reports that show that the exogenous gibberellic acid (GA) stimulates runner formation and inhibits flowering. Moreover, cytokinin (CK) induces flowering in several plant species. According to our results, it is possible that the endogenous GA level is lowered and endogenous CK level is raised under blue LED light.