## 3 Light Effect on Growth and Development of _C. sativa_
### Effect of Light Intensity in Growth and Metabolism of C. sativa
Such integration optimizes plant development evaluations, refining our comprehension of co-active physiological processes [51] (Table 1). By meticulously modeling diverse physiological responses to critical environmental factors, this revolutionary approach promises to redefine plant tissue culture methods with unprecedented precision. The insights gleaned from this system will guide the evolution of in vitro micropropagation techniques and the strategic application of precision LEDs, elucidating the complex relationships between light intensity, quality, and sugar metabolism in plants--dimensions often neglected or challenging to conceive (Table 1). This innovative system stands as a beacon of progress, poised to revolutionize plant tissue culture and cultivation practices, enhancing precision and efficiency to an unprecedented degree [51]. _C. sativa_ metabolites, particularly phenolic and terpene compounds like cannabinoid and cannabinoid (Figure 1), have immense medicinal value and potential for treating numerous incurable diseases. Light intensity is a critical factor influencing the synthesis of these potent plant metabolites. In a groundbreaking study on industrial _C. sativa_ 'Yunma 1', researchers used advanced UPLC-MS/MS wide-target metabolomics technology to analyze the metabolic profile under various light intensities (Table 1) (30, 80, 130, and 180 umol m\({}^{-2}\) s\({}^{-1}\)) [49]. The findings were definitive: light intensity profoundly impacts the _C. sativa_ metabolic profile. At 180 umol m\({}^{-2}\) s\({}^{-1}\), levels of lipids, phenolic acids, flavonoids, amino acids and their derivatives, organic acids, alkaloids, nucleotides and their derivatives, sugars, alcohols, vitamins, cannabis, coumarins, lignans, and terpenoids were highest [49]. However, the synthesis of critical secondary metabolites, spirodienone, and iso-spirodienone (cannabispiadienone) peaked at 80 umol m\({}^{-2}\) s\({}^{-1}\). Additionally, the concentrations of phenolic acids and flavonoids reached their maximum at 130 umol m\({}^{-2}\) s\({}^{-1}\), corroborating previous research (Table 1) [49]. These results provide a crucial foundation for understanding the metabolic characteristics of specific secondary metabolites and identifying optimal conditions for their synthesis. This study underscores the paramount importance of light intensity in maximizing _C. sativa_ metabolite production, setting a new standard for precision in agricultural practices [49]. Growth, Development, and Secondary Metabolism: Combined Effect of Light Spectrum, photoperiod and Intensity on C. sativa  
Research on light studies has primarily concentrated on assessing the isolated impacts of either spectral quality or photosynthetic photon flux density (PPFD) on inflorescance mass and concentrations of plant secondary metabolites (PSMs). However, there is an increasing awareness, evidenced in various plant species, that the interplay between spectral composition and PPFD significantly influences plant dry matter accumulation and PSM concentrations (Figure 1) [65]. In the context of medical cannabis cultivation, which utilizes diverse spectra and PPFD levels, the interactive effects of these factors on inflorescence mass and PSMs are garnering significant interest from both industrial stakeholders and the scientific community [65]. LED fixtures vary in their spectral output, from narrow to broad bandwidths, which can influence plant growth. Broadband spectra may provide more balanced light exposure and enhance plant dry matter production. Given the variability in plant responses to different spectra and PPFD, it is crucial to select appropriate lighting tailored to the needs of medical cannabis, though significant knowledge gaps remain in this area. Recent investigations reveal a profound synergy between light spectrum and PPFD on dry matter production and inflorescence yield in medicinal cannabis [65].