active growing period. Moreover, twilight far-red light (FRL) treatment advanced the leaf bud burst of silver birch [5; 6]. These examples indicate that the ratios and intensities of the individual spectral components should be controlled adequately in the plant growth chambers and glasshouses in order to obtain correct experimental results. To perceive light signals from the sun, plants have different types of photoreceptors which include phytochromes (Phy), cryptochromes (Cry), phototropins (PHOT), and UV RESISTANCE LOCUS 8 (UVR8) [7; 8; 9]. Among photoreceptors, Phys (mostly phytochrome A (PhyA) and phytochrome B (PhyB)) perceive FRL and red light (RL). Phys oscillate between their active and in-active forms depending upon the R:FR ratio, which results in shade avoidance syndrome (SAS) responses [10]. Crys perceive both BL and green light (GL) signals [10; 11; 12]. PHOTs are also involved in the sensing of BL [13; 14]. The UVR8 photoreceptor perceives UV-B radiation [15; 16]. Physiological and molecular studies have shown the coordinated action of different photoreceptors, a phenomenon known as photoreceptor coaction [17]. For instance, the study on phytochrome-deficient _Arabidopsis_ (_Arabidopsis thaliana_ ([PERSON]) mutants showed that phytochrome (either A or B) is necessary for Cry1-regulated suppression of hypocotyl elongation. Further analysis revealed that Cry1-mediated BL response was inhibited in phytochrome-deficient mutants, even though Cry was unaffected in the genetic background of these mutants, as shown by western-blot analysis [18]. An earlier study on _Arabidopsis_ mutants indicated that both phyA and phyB control the reaction of plants to RL, whereas BL-mediated response is also influenced by phyA and Cry1 [19]. However, further studies are required to investigate the spectral control of the co-action of photoreceptors and the involvement of the redox system in this process. Phys and Crys control various biochemical processes through their effects on different regulatory proteins. Thus, they inactivate the photomorphogenesis repressors CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) and phytochrome interacting factors (PIFs), which leads to the nuclear stabilization of the bZIP transcription factor ELONGATED HYPOCOTYL5 (HY5) [8]. HY5 is the master regulator of photo-morphogenesis; furthermore, it can bind to the promoter region of more than 9000 genes and directly regulates approximately 1100 of them [20; 21]. HY5 can transmit light signals from a wide range of the light spectrum (e.g., UV, blue, red, FR) to light-regulated genes, including those associated with various metabolic pathways. AtHY5 has a DNA-binding domain but lacks any transcription activator domains; thus, it must cooperate with other transcription factors having such domains for the regulation of target genes [22; 23; 24; 25]. HY5 maintains the appropriate PSII activity by controlling the balance between the oxidants and antioxidants [26; 27; 28], which protects the photosynthetic apparatus against oxidative stress under unfavourable environmental conditions [29; 30; 31]. HY5 mediates FRL induction of TANDEM ZINC-FINGER/PLUS3 (TZP) expression by directly binding to a G-box motif in the TZP promoter. Furthermore, TZP physically interacts with COP1, which inhibits COP1 interaction with HY5, ensuring its feedback regulation [32]. Almost all plant species can convert light energy into chemical one by reducing CO\({}_{2}\) during photosynthesis, which ensures energy and reduces power for the whole metabolism [33]. The spectral range of sunshine, which is used for photosynthesis, is from 400 to 700 nm (known as PAR). However, plants respond to wavelengths ranging from the UV (280\(-\)400 nm) to the FR (700\(-\)800 nm) region of the spectrum, which is covered by the sensitivity of various photoreceptors.