## 4 Discussion  
This study demonstrates that terpenoids are the primary volatile compounds in calamondin flowers across four developmental stages. The main terpenoids identified were linalool, \(\beta\)-ocimene, \(\alpha\)-farnesene, and \(\beta\)-pinene. These results align with studies on pomelo flowers, where terpen were the predominant compounds, comprising 36.98-65.69% of the total volatiles [27]. In nine _Citrus_ cultivars, monoterreponoids were the major volatile class in flowers, accounting for at least 60.20%, with linalool and limonene being the top two volatiles at all blooming stages [28]. In _Rosa willmotiae_ flowers, essential substances included alcohols and terpenoids across three flowering stages [29]. The terpenoids in calamondin flowers might play a crucial role in attracting pollinating insects, though this requires further empirical evidence. Additionally, the major components linalool, \(\beta\)-ocimene, \(\alpha\)-farnesene, and \(\beta\)-pinene are compounds with distinct floral or fruity odors [30], which further emphasize the ornamental value of calamondin's floral scent. The primary ester volatile compound detected across all four stages was methyl anthranilate. During the half-open and full bloom stages, the relative content of esters was higher than aromatics, while the opposite was true for the bud and senescence stages. The volatile compound profiles of the bud and senescence stages were similar, as were those of the half-open and full bloom stages. Major volatiles identified in intact graprefruit, sweet orange, sour orange, mandarin, lemon, lime, and pummelo blossoms included linalool, \(\beta\)-myrcene, \(\alpha\)-myrcene, limonene, (\(E\))-ocimene, methyl anthranilate, and indole [31]. Methyl anthranilate, with its typical floral and fruity scent [30], might contribute to the more appealing aroma of calamondin flowers. However, the current content of ester compounds in calamondin's floral scent is relatively low. In the future, the content of methyl anthranilate and other ester compounds could be enhanced through genetic improvement or external factors, further improving the floral scent of calamondin. Different flowering stages significantly influenced the volatile profile. This study found that the total VOC content increased from the bud stage to the half-open stage, peaking at the half-open stage, and then gradually decreased from the half-open stage to the senescence stage. Similarly, the total content of volatiles in pomelo flowers increased from stage-I to stage-III [27]. In crabapple flowers, the total amount of volatile compounds released showed an initial increase followed by a decrease from the bud stage to the end of flowering [32]. The aroma volatiles of nine citrus cultivars indicated that the highest amounts of volatiles were present in fully opened flowers, especially in Huyou and lemon [28]. The results indicate that the half-open and full bloom stages are the best periods for appreciating calamondin floral scent. Therefore, it is advisable to focus on these blooming stages when planning garden fragrance landscapes and potted plant sales, as selecting plants with flowers at the half-open and full bloom stages can maximize the floral scent effect. The trends of different substances varied significantly across developmental stages. PLS-DA analysis identified five key terpenids with differential emissions, including limonene, linalool, \(\beta\)-pinene, germacrene D, and \(\beta\)-ocimene. Among them, linalool, \(\beta\)-pinene, and \(\beta\)-ocimene were the compounds with the highest relative content, further supporting their crucial role in the quality of calamondin floral scent. These key VOCs have also been reported in previous studies. For example, linalool and limonene were the top two volatiles at all blooming stages in nine citrus cultivars [28]. Linalool, the most abundant compound, was also reported in pomelo and graprefruit flowers, gradually increasing during growth and becoming the most abundant compound at stage-III in pomelo flowers [27].