## 3 Light Effect on Growth and Development of _C. sativa_
### Light Spectrum in Cannabis Growth, Development, and Metabolism
Phenolic compounds, with their formidable radical-scavenging capabilities and protein interactions, are key players in antioxidant defense [68]. In groundbreaking research, various biopreparations, including vesicular-arbuscular mycorrhiza (VAM), _Azotobacter chroococum_, and _Trichoderma_ spp., were inoculated on _C. sativa_ seeds and/or substrates, then exposed to blue and white light. The findings were stark: blue light dramatically undermined bio-preparation treatments (Figure 1), leading to significantly lower morphological parameter values compared to controls (Table 1) [61]. Yet, blue light-induced higher leaf pigment levels. Crucially, the type of light did not alter the antioxidant properties, including DPPH(2,2-diphenyl-1-(2,4,6-trinitrophenol) hydroxyl), FRAP (ferric reducing antioxidant power), flavonoids, total flavonoid content, or phenolic acids (Figure 1) [61]. Biopreparation treatments also did not markedly influence leaf pigment content (Chl a, Chl b, and carotenoids) or phenolic and flavanol content (Figure 1). These revelations demand further investigation, particularly over prolonged periods or under field conditions, to unlock the full potential of bio-preparation treatments with beneficial microorganisms on the Finola _C. sativa_ cultivar [61]. The implications are profound, offering a path to revolutionize _C. sativa_ cultivation with enhanced growth, resilience, and biochemical richness [61]. Monochromatic blue light stands as a formidable tool for enhancing secondary metabolite production, though it can significantly impair growth traits like inflorescence size. Strategic, intermittent supplementation with blue light at the terminal stage of the growth cycle [30] shows great potential for dramatically elevating THC levels without substantially diminishing biomass [58]. Dichromatic LED lighting emerges as a groundbreaking alternative, mitigating the adverse effects of pure blue light while sustaining secondary metabolite levels comparable to conventional HPS lighting. An innovative study scrutinized the impact of six distinct light spectra from dichromatic B LED lights on the growth traits and secondary metabolite profiles of _C. sativa_ (Babbas Erkle Cookies') [58]. These spectra included blue (430 nm), red (630 nm), rose (430 + 630 nm, 1:10 ratio), purple (430 + 630 nm, 2:1 ratio), and amber (595 nm) LEDs and an HPS control. Blue light treatment yielded the highest THC concentration but the lowest THC per plant, whereas the HPS treatment produced the highest THC per plant. Blue light also markedly increased cannabinoid (CBG) and terpene concentrations but had a limited effect on cannabinoid (CBD) biosynthesis (Table 1) [58]. These groundbreaking findings empower producers to tailor spectral designs to specific production objectives, thereby optimizing cannabis production efficiency and slashing operational costs. Future research should be on light qualities richer in the amber spectrum and fine-tuning blue light proportions. Hybrid grow rooms integrating HPS and LEDs could substantially boost light intensity and profitability. _C. sativa_ seedlings were meticulously evaluated under 11 light treatments within an advanced aeroponics system, assessing morphological traits, photosynthetic pigments, and osmolytes (Figure 1) [58]. Treatments L10 (R4/B2) and L11 (R2/B2/G2) excelled in leaf and node numbers. Treatments L2 (white), L3 (R8), and L5 (R7) achieved superior leaf length and width. Exceptional shoot lengths were noted in L3, L6 (R6), and L9 (R6), while root development flourished in L1 (natural light), L5, and L9. L3 exhibited the highest levels of chlorophyll a, chlorophyll b, and photosynthetic quantum yield (Fv/Fm) (Table 1) [37; 69]. Hierarchical clustering analysis revealed that higher leaf and node numbers resulted in bushier plants with shorter shoots and longer roots. There was a stark negative correlation between photosynthetic traits and osmolytes with root length (Figure 1).