## 1 Introduction
The synthesis of auxins at the plant apex and their strategic transport to axillary buds play a crucial role in maintaining apical dominance [17; 25; 26; 27]. These mechanisms are key to understanding plant growth and development in response to light signals and underscore plant adaptability and resilience [17; 25; 26; 27]. Synchronized flowering is crucial for plants, particularly in regions with significant seasonal variation and those requiring cross-pollination [26; 28]. Because flower and seed development are energy-intensive processes, they must occur under optimal conditions. Therefore, flowering is meticulously regulated by environmental factors such as day length and temperature, as well as internal signals, including hormonal levels, sugars, and plant age (Figure 1) [26]. Phytochromes A and B (Phy A and Phy B) and cryptochrome 2 (cry2) are crucial photoreceptors that mediate photoperiod flowering [26]. Different hormones further influence this process. Understanding how these environmental cues and hormonal signals interact is key to deciphering the mechanisms that govern the timing of flowering in plants [26]. Light conveys critical environmental information to plants influencing defense hormone signaling, resource allocation, and adaptation [27]. Jasmonate (JA) and salicylic acid (SA) are powerful defensive phytohormones, and their pathways are profoundly influenced by light, impacting plant defense, growth, and development (Figure 1). Photoreceptors and transcription factors in phototransduction are integral to these hormones' signals [27], significantly advancing the use of artificial lighting for crop growth and disease management in greenhouses. Jasmonate orchestrates the accumulation of vital defense-related metabolites and proteins, along with MYB, and trichome-specific transcription factors that play crucial roles in UV light signaling and terpenoid production (Figure 1). The light spectrum significantly controls terpenoid biosynthesis and determines plant quality, including aroma, flavor, color, and medicinal properties [27]. Light conditions such as blue, red, and far-red light enable HY5 to drive secondary metabolite production. In Artemisia annua, HY5 binds to specific transcription factor genes, dramatically upregulating their expression and fueling polyphenol, terpenoid, and alkaloid biosynthesis [27; 28; 29; 30; 31]. Artificial lighting, such as high-pressure sodium (HPS) lamps, light-emitting diodes (LEDs), and fluorescent lamps, are crucial for indoor cannabis cultivation to meet the light energy needs of the plants. Over the past decade, the use of LEDs in horticulture has skyrocketed due to their overwhelming advantages over traditional light sources (Figure 1). LEDs boast unparalleled energy efficiency, minimal heat emission, and exceptional longevity. They offer superior efficacy and significantly lower operating costs compared to HPS lamps [5; 16]. They can emit specific wavelengths, enabling groundbreaking research on the effects of different wavelengths on secondary metabolite production, although data on the effects of varying radiation intensities and qualities on cannabis secondary metabolite composition are limited and sometimes contradictory [5; 16]. LED adoption has revolutionized horticultural practices by enabling growers to customize the light spectrum and intensity for different crops and developmental stages, thereby enhancing production schedules, crop yield, and quality. Traditionally, high-intensity discharge (HID) lamps like metal halide (MH) and high-pressure sodium (HPS) lamps have dominated greenhouses and growth chambers (Figure 1) [5; 16]. However, the exploration of monochromatic LED systems as replacements for traditional light sourcesis underway, particularly in space greenhouses, to optimize crop production and quality through meticulously designed light recipes. By combining LEDs of various colors, growers can create a tailored light spectrum at the desired intensity, effectively modulating different plant functions [5; 16].