Light quality modulates light signal perception and
transduction
In natural conditions, plants encounter varying light spectral
conditions. For example, in the latitudes close to Arctic circle, the
radiation flux from a distinct solar spectrum (UV-A/B ratio, blue and
red/far-red wavelengths) changes compared to southern latitudes and this
has been shown to favor higher accumulation of flavonoids in northern
vegetation, including wild bilberries (Jaakola & Hohtola 2010; Zoratti
et al., 2014a). Delphinidins are the major class of constituting
anthocyanins found abundant in northern clones compared with higher
cyanidin proportions found in southern clones (Zoratti et al., 2016).
Also, in forests the top canopy absorbs most of the essential red and
blue wavelengths and only the green and far-red wavelengths are
reflected by foliage to lower parts of the plant (Holopainen et al.,
2018). In bilberry, populations grown under direct sunlight have
demonstrated increased bioactive compounds and bioavailability compared
with plants growing under forest canopy (Eckerter et al., 2019).
However, the even distribution through the foliage can be achieved by
modern energy efficient LEDs because the irradiation maxima from these
supplemental lightings are often higher than plant’s absorption peaks.
Our study showed that during the red light LED treatment, PhyBexpression was upregulated together with COP1 and HY5 , the
key genes involved in photomorphogenesis, alongside
photoperiodism-related early flowering (ELF3 ) and CK2αgenes (Figure 5). On the other hand, the blue light up-regulated
cryptochrome (CRY2 ) but down-regulated COP1 and HY5in tandem as its photoreactive mechanism which might reveal an early
photomorphogenesis occurred upon light treatment as a spontaneous
response. It is also to be noted that bHLH6 (MYC2), which is a
negative regulator of blue light induced photomorphogenesis and was
positively expressed (Yadav et al., 2005), might have played a crucial
role in blue light signaling mechanism.