2019 Volume 18 Issue 4 Pages 417-422
The relationship between red/far-red ratio (R/FR ratio) of LED chips and flowering inhibition, by LED light sources with the same power consumption, was evaluated using two cultivars of chrysanthemum, the autumn flowering ‘Jimba’ and summer-to-autumn flowering ‘Iwano-hakusen’. The combinations of light intensity of the R and FR LED chips emitting at wavelengths of 632 nm and 734 nm, respectively, were set as 5 : 0, 4 : 1, 3 : 2, 2 : 3, 1 : 4, and 0 : 5. The six LED light bulbs were divided into short- and long-term lighting to detect differences in the effects of flowering inhibition due to differences in light quality. The long- and short-term lighting treatments were set at 4 h and 30 min, respectively, for ‘Iwano-hakusen’ and 2 h and 4 min, respectively, for ‘Jimba’. In the short-term lighting treatment, a high flowering inhibitory effect was obtained with the R5:FR0 chip combination in both cultivars. In long-term lighting treatment, the responses to light quality differed between the cultivars: flowering inhibition in ‘Iwano-hakusen’ was highly effective at R3:FR2 and R2:FR3; however, in ‘Jimba’ a marked inhibitory effect was obtained at R5:FR0. Long-term lighting by R + FR light resulted in a high flowering inhibitory effect in ‘Iwano-hakusen’. This suggested the involvement of high irradiation response via the phytochrome phyA.
