Budding and Bolting Responses of Horticultural Plants to Night-break Treatments with LEDs of Various Colors

We investigated the use of light-emitting diodes (LEDs) of particular wavelength emissions as light sources for night-break treatment of plants. We used the long-day plants godetia (Godetia cvs.), petunia (Petunia×hybrida Vilm.), and spinach (Spinacia oleracea L., two cultivars); and the short-day plants perilla (Perilla ocymoides L.), cosmos (Cosmos bipinnatus Cav.), yellow cosmos (Cosmos sulphureus Cav.), zinnia (Zinnia elegans Jacq.), and Japanese morning glory (Pharbitis nil Choisy). The plants were exposed daily to LED irradiation from 2300 to 0100h during the short-day season (late autumn to early spring). Red and orange LED lights were effective in controlling flowering in all plants used in this study. Yellow and green LEDs were almost as effective. Far-red LED was effective in some, but not all, cases. One spinach cultivar bolted in response to far-red night-break treatment, but the other cultivar did not. Blue LED was effective in only one trial with perilla, but not so effective in other cases.