## 3 Discussion
### Flowering  
The DVB (days from treatment initiation to visible flower bud) was higher in the NI-RB, NI-FrR, NI-FrW, and NI-WR treatments than the SD control (Table 1). This suggests that B, R, W, and Fr light receptors had an antagonistic effect on the promotion of flowering in chrysanthemum plants. The shortened DVBs in the NI-BFr and NI-FrB treatments (Table 1) suggest that in chrysanthemum (a SDP), flowering was promoted by the synergistic effects of B and Fr light. In a combined shifting treatment of B and R light or B and W light, the NI ending with B light (NI-RB and NI-WB) induced flowering. Thus, it is probable that the B light receptor can enhance floral-inducer activity, resulting in a higher energy requirement for the promotion of flowering. Previously, it was reported that Fr and B light promote flowering, whereas R light often inhibits it [12]. However, in both the combined R and Fr light treatment (NI-RFr and NI-FrR), and the Fr and W (NI-FrW and NI-WFr) light treatment, flowering was not affected by changes in the light quality of the NI. These findings suggest that the _P_/_P_\({}_{\mathrm{fr}}\) ratio might have a bigger impact on flowering than the effects of changes in the light quality of the NI. In many SDPs, the NI is effective only when the supplied dose of light is sufficient to fully photoconvert all Pr (the phytochrome that absorbs R light) [40]. A subsequent exposure to Fr light, which photoconverts the pigment back to its physiologically inactive _P_\({}_{\mathrm{r}}\) form, restores the flowering response.  
In this study, taller plants due to Fr light produced more flowers per plant, and this could be explained by two reasons. The increase in the number of flowers per plant in the NI-BFr light (Table 1) might be due firstly to high light energy induction and evasion of darkness in the shoot with longer internodes, which is known as the shade avoidance response. The reactions in response to shade avoidance are all initiated by a single environmental signal: the reduction in the ratio of R to Fr radiation (_i.e._, R:Fr) that occurs within crowded plant communities [41]. This shade avoidance response is characterized by increased hypocotyl, stem, and petiole elongation; a more erect leaf position; increased apical dominance; and early flowering [42; 43]. When grown in a close proximity to neighboring plants, many species grow elongated stems and smaller leaves, a behavior referred to as the shade avoidance response [44]. This response increases their ability to access sunlight by growing taller than other plants, and thus constitutes a competitive advantage [44]. This increase in the height growth could results in an increase in penetration of light energy through the canopy; leading to the increased production of photosynthetic assimilates during the photoperiod, due to increased stem growth and the development of a larger number of axillary buds. The second reason for the increased number of flowers in the NI-BFr light could be due to B light-related photoreceptors playing important roles toward inducing the flowering responses [45; 46]. This finding on the increase in the number of flowers per plant in the NI-BFr light suggests that the B and Fr light, when given in this order, has a synergistic effect on the increase of the number of flowers per plant.