## 1 Introduction  
_Aquilaria sinensis_ (Lour.) Spreng. belongs to Thymelaaceae _Aquilaria_. It is a rare medicinal plant endemic to China [1], and it is mainly found in evergreen broad-leaved mixed forests in low-altitude mountains and hills, such as those in Guangdong, Hainan, Fujian, Yunnan, and Taiwan. Agarwood is often used in the production of drugs, as it has sedative, aphrodisiac, cardiotonic, antietic, anti-asthmatic, neurooregulatory, anti-inflammatory [2], antibacterial, antitumor [3], antidepressant [4], antioxidant [5], hypoglycemic, hypolipid-demic, antipyretic, and analgesic effects, with additional therapeutic potential against diabetes [6, 7] and Alzheimer's disease. It is considered by the _Pharmacopeia of the People's Republic of China (2020 Edition)_ to be the only plant source of Chinese agarwood. Agarwood formation in _A. sinensis_ is a result of the host's defensive response to mechanical damage,insect attack, or microbial invasion [8; 9], and a healthy plant will not produce this product without such external damage or stimulation. Despite research having been carried out over the past 100 years, agarwood formation mechanisms are still controversial and have not yet been clarified. There are five main hypotheses: the pathological hypothesis [10], the non-pathological hypothesis (physical and chemical injury induction hypothesis) [11], the traumatic pathology hypothesis, the defense response induction hypothesis, and the elicitor induction hypothesis. These hypotheses represent the foundation for the study of the formation mechanisms of agarwood. However, these existing hypotheses have limitations. One limitation is that each hypothesis attempts to explain complex phenomena with a single dominant factor (e.g., fungi, oxidation, genes), but agarwood formation is fundamentally a result of synergistic interactions among multiple factors, including biological (fungi, insects), chemical (oxidation, enzyme catalysis), physical (damage, environmental stress), and genetic (gene expression) factors. Second, these studies overlook the temporal dynamics. Natural agarwood formation takes decades, but most existing research is based on short-term experiments (months to years), which fails to capture long-term processes, such as resin synthesis, oxidative polymerization, and microbial community succession. Third, there is a lack of strong interdisciplinary integration. Chemical analyses are often conducted in isolation from the ecological context (e.g., overlooking the role of symbiotic microorganisms), and biological research is insufficiently linked to the functions of specific compounds, resulting in a fragmented understanding of agarwood formation mechanisms. These problems deserve our further attention. Many agarwood induction techniques have been widely examined. At present, methods for creating agarwood are divided into three categories. One is the physical trauma method [12; 13], including the chiseling method, the chopping method, the fire stud method, the trunk burning method, the semi-trunk breaking method, full-trunk breaking method, or the branch breaking method; the second is the artificial inoculation induction method [14; 15]; and the third is the chemical induction method. These induction methods greatly promote the efficiency of agarwood output. Of course, artificial induction technology for agarwood is still developing. Although the formation time of agarwood has been shortened to a certain extent and output efficiency has improved, the quality of the agarwood produced has not yet reached that of wild agarwood, and the induction technology needs to be improved further. The authenticity of agarwood on the market is difficult to determine, and the quality is varied. Authentic agarwood has a special aroma and bitterness, the surface is uneven, and it contains more oily substances than its artificially induced counterpart [16]. Counterfeit agarwood is mainly derived from heartwood, such as _Caesalpinia sappan_, _Pinus masoniana_, and _Dalbergia_.