## 1 Introduction  
Terpenoids are the largest class of secondary metabolites found in living organisms, including plants, animals, microbes, and fungi [1, 2, 3]. Their skeleton is composed of isoprene units, with the number of these units determining the terpenoid type, including monoterpenes (C\({}_{10}\)H\({}_{16}\)), sesquiterpenenes (C\({}_{15}\)H\({}_{24}\)), and diterpenenes (C\({}_{20}\)H\({}_{32}\)) [4]. Plant terpenoids have dual roles, serving as both essential primary metabolites for growth and precursors for specialized secondary metabolites, such as gibberellins, caroten, and chlorophylls [5]. Over recent years, terpenoids have attracted considerable attention from the pharmaceutical industry because of their diverse chemical properties, with both terpenoids and their derivatives demonstrating good antibacterial and antioxidant activities. Examples include elemene, a natural compound with anticancer effects [6], as well as \(\alpha\)-pinene, paclitaxel, and citral [7]. Notably, taxol in _Taxus brevifolia_, artemisinin in _Artemisia annua_, and ginsengides from _Panax ginseng_ have demonstrated significant potential in disease prevention and treatment [8; 9; 10]. Monoterpenoids, a prevalent subclass of plant secondary metabolites, have garnered significant attention owing to their multi-functionality, including as antimicrobials and antioxidants, and important chemical components in plant essential oils [11; 12]. Environmental factors, including light, which is essential for plant growth and development, are recognized as key regulators of terpenoid biosynthesis. Studies have shown that light induces changes in seedling morphology, participates in seed germination, and triggers flowering [13; 14; 15; 16]. However, the molecular mechanisms underlying the effects of light on secondary metabolism remain unclear. Notably, the light-dependent regulation of fruit-specific metabolites, as exemplified by the industrially valuable monoterpenes (e.g., citral) in _L. cubeba_, remains under investigated. The biosynthetic pathways of terpenoids in plants have been well characterized, and it is known that monoterpene production primarily occurs through the mevalonate (MVA) and methylerythnitol phosphate (MEP) pathways [17; 18; 19; 20]. Ternenoid yield is mainly governed by the efficiency of synthesis of the universal isoprenoid precursors isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). These structural units are converted into terpenoid precursors by key terpenoid biosynthetic enzymes such as terpenen synthases (TPS) [1; 4]. Understanding the source of terpenoids and clarifying their synthetic pathways and associated regulatory mechanisms can provide strong support for the utilization of terpenoids in food and pharmaceutical industries. Environmental factors such as light, temperature, drought, and biotic/abiotic stress greatly influence the growth and development of plants, both woody and herbaceous [21; 22]. Light plays an essential role in plant secondary metabolic processes, not only providing a source of energy for photosynthesis but also acting as a regulator of plant metabolism and responses to stress [23]. An increasing number of studies have investigated the effects of light on the biosynthesis of plant secondary metabolites, mainly focusing on anthocyanins, sesquiterpene products, artemisinin, and flavonoids [6; 24; 25]. For instance, in _Solanum melongena_ L., light has been shown to modulate anthocyanin accumulation by triggering _SmCRY-SmCOP1_ interactions, subsequently leading to the suppression of _SmHY5_ and _SmMYB1_ expression [25]. In ginkgo leaves, it was found that the expression of flavonoid biosynthesis-related genes decreased with decreasing light intensity, accompanied by a reduction in the total flavonoid content [26]. Notably, light intensity directly impacts terpenoid production through the modulation of the MEP pathway [27].