## 3 Discussion
### Photoreceptor Gene Expression Analysis  
The _phyA_ mediates the promotion of flowering by Fr light [47; 48]. In contrast, _phyB_ acts in a partially redundant manner with _phytochrome D_ (_phyD_) and _phytochrome E_ (_phyE_), mediating the inhibition of flowering by R light [34; 49; 50; 51; 52]. However, the function of _phyB_ in floral initiation may be more complex than a simple floral inhibitor. The _cry1_ and _cry2_ act redundantly to mediate the promotion offlowering by B light [48, 53]. Photoperiodic floral initiation is regulated by a systemic flowering inducer (florigen) and inhibitor (antiforigen) such as the _FTL_ and _AFT_ genes, respectively, which are produced in the leaves [54]. The flowering that occurred in the NI-FrB treatment, even when the _phyB_ gene (which is thought to be a flowering inhibitor gene) was expressed may be caused by high levels of expression of the flowering promotor genes _phyA_ and _cry1_ (Figure 3A-C). The _phyB_-mediated antiforigen production system plays a predominant role in the obligate photoperiodic flowering response in chrysanthemum, allowing the strict maintenance of the vegetative state under non-inductive photoperiod conditions [54]. In the NI-RW treatment, even though a high level of _phyA_ gene expression was induced, the plants did not flower (Figure 3A). Similarly, the lack of flowering was observed in the NI-BR treatment, in spite of high levels of _cry1_ and _FTL_ expression (Figure 3C,D). In this treatment, it is thought that although the first 2 h of NI with B light promoted flowering by stimulating the expression of the _cry1_ and _FTL_ genes, flowering was suppressed by exposure to R light during the last 2 h of the NI and/or interactions among the flowering-related genes. The absence of flowering that was observed even when the _FTL_ gene was highly expressed in the NI-RFr treatment may be due to the high expression levels of the _phyB_ and _AFT_ genes observed in that treatment (Figure 3B,D,E). Based on the results in the NI-BR and NI-RFr treatment, it is assumed that the R light has relatively large, while the Fr light has relatively small, effect on flowering in chrysanthemum. The flowering-suppressing _AFT_ gene was most highly expressed in the NI-RFr treatment, in which flowering was not observed as expected, and slightly expressed in the NI-WB treatment, in which plants did flower. It is assumed that R light has more effect on flowering in chrysanthemum than W light. The overall expression patterns of photomorphogenic genes observed in this study are different from those observed in previous studies, as described in the previous paragraph. These differences might be due to the use of different chrysanthemum genotypes, differences in the experimental environment, or differences in sample collection time, the plant part from which the samples were collected, and the specific wavelengths of light produced by the LEDs used in each study. It seems contradictory to have similarly low levels of most photoreceptor genes in both inductive (SD) and noninductive (LD) treatments. The real reason for low expressions of most photoreceptor genes in both LD and SD treatments relative to the NI treatment is not clearly explainable. It could be that the expression level of these genes changes over time, presumably the greatest at the early stage of flowering induction and gradually decreasing afterward. Thus, it might be necessary to test whether \(\leq\)4 h of NI treatment with specific wavelengths and at considerably lower PPFs than currently employed can be used to suppress flowering in chrysanthemum, a qualitative SDP. The practical applicability of the light quality shifting of NI treatments in commercial crop production systems needs to be investigated in cases where the goal is the prevention of physiological disorders caused by light contamination during the dark period. In potted plants, consumers usually prefer smaller plant height. Therefore, B light has potential practical applicability for potted floricultural crops.