## 3 Light Effect on Growth and Development of _C. sativa_
### Effect of Light Intensity in Growth and Metabolism of C. sativa
Plant height diminished with higher light intensities, but stem diameter and biomass reached their zenith at 130 umol m\({}^{-2}\) s\({}^{-1}\). This intensity also minimizes stress on amino acids and soluble protein content. For specific metabolites, 30 umol m\({}^{-2}\) s\({}^{-1}\) proved optimal for amino acids and soluble proteins, whereas 180 umol m\({}^{-2}\) s\({}^{-1}\) was superior for soluble sugars (Figure 1). Light intensity profoundly influenced crucial metabolites such as arginine, cysteine, isoleucine, leucine, methionine, phenylalanine, proline, maltose, fructose, glucose, and sucrose (Figure 1). The study conclusively demonstrated that industrial _C. sativa_'s morphological characteristics and metabolite profiles respond dramatically to varying light intensities. Achieving optimal results requires meticulously chosen light intensities tailored to specific objectives. These groundbreaking findings underscore that optimal light intensity can significantly enhance plant growth, amino acid content, soluble protein levels, and soluble sugar concentrations (Figure 1). This study sets a new standard for agronomic excellence, providing pivotal insights for future research and the cultivation of industrial _C. sativa_ (Table 1) [47]. In the realm of indoor cannabis production, the propagation, vegetative growth, and flowering stages each demand meticulously tailored photoperiod and light intensity (LI) requirements [48]. Cannabis crops, depending on genotype, spend a critical 6 to 12 weeks under a stringent 12 h flowering photoperiod to reach peak maturity for harvesting. The vegetative stage, despite its brevity, imposes an intense energy demand due to significantly higher LIs and extended photoperiods (\(\geq\)16 h) compared to the flowering stage. Achieving the optimal post-vegetative stage morphology is paramount and varies based on the cultivator's production system [48] (Table 1). The overarching goal is to ensure exceptional transplant success and robust vegetative growth. During the vegetative stage, LI plays a crucial role in shaping vital plant growth attributes such as height, stem thickness, branching, leaf size, leaf thickness, and biomass partitioning. These attributes are critical for the plant's resilience and productivity as it transitions to flowering. Therefore, selecting the precise LI during this stage is essential to forge a formidable foundational structure, characterized by thicker stems and abundant nodes, which underpins prolific inflorescence development--accounting for more than half of the total aboveground biomass at peak maturity [48]. In a pivotal study exploring the impact of a wide range of LIs on vegetative-stage cannabis morphology and growth attributes under exclusive LED lighting, it was conclusively demonstrated that PPFD levels between 600 and 900 \(\mu\)mol\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\) struck the perfect balance. This range optimized key morphological parameters while curbing energy consumption associated with excessively high LIs. These groundbreaking findings empower cultivators with the knowledge to fine-tune their LI strategies, harmonizing growth and morphological excellence with the economic imperatives of energy efficiency. While the ideal morphological and growth attributes of vegetative-stage cannabis plants are subjective to each genotype and production scenario, the identified LI response patterns offer cultivators a powerful tool to maximize their production goals [48] (Table 1). This optimization not only enhances growth and morphological characteristics but also judiciously balances the economic returns against the elevated input costs of providing more PAR to their crops [48]. This study sets a new benchmark for excellence in indoor cannabis cultivation, guiding the industry towards unparalleled efficiency and productivity. Micropropagation revolutionizes the rapid and effective propagation and maintenance of uniform plantlets in sterile cultures, proving invaluable to high-value industries such as the burgeoning cannabis sector [51].