## 3 Discussion  
The types and contents of volatiles in flowers determine the aromas and functions of flowers. To date, VOCs in the Chinese rose and lily plants have been determined through headspace microextraction and gas chromatography-mass spectrometry [14; 15; 16; 17]. A total of 47 VOCs were detected in both the rose [14] and lily [15], 43 VOCs were detected in _Nymphaea hybrid_[16], and 53 VOCs were detected in _Panax notoginseng_[17]. In this study, a total of 926 volatile compounds were detected in _C. mollissima_, which is much higher than that in other plants. This may have been determined by the sampling and testing methods. For the volatile compounds of lily and Chinese rose flowers, fresh samples were used, and the samples were ground to determine their volatile components directly [14; 15; 16; 17]. Only 21 volatile compounds could be identified in chestnut flowers without grinding the samples [7]. The Japanese chestnut infloresence was determined after the extraction of essential oils, and 72 volatile substances with a content greater than 0.01% were identified [18]. In this study, chestnut flowers were frozen in liquid nitrogen and ground into powder, then put into a headspace bottle, dissolved in saturated NaCl, and shaken at 60 \({}^{\circ}\)C for 5 min. Then, the volatile components were detected. This method allows for the identification of more volatile substances, which is beneficial for the study of the anabolic processes of volatile substances [19; 20; 21]. In this study, the VOCs of chestnut flowers were mainly terpenes, heterocycles, esters, hydrocarbons, ketones, alcohols, aromatic hydrocarbons, and other substances, which are similar to those of most other plants [15; 22; 23]. During the FFS period, the relative contents of acetophenone and styrene in the metabolic pathways of \(\beta\)-pinene and ethylbenzene, which are the main components of the Chinese chestnut's floral fragrance, were all greater than 5%. This result is similar to the VOCs in chestnut and Japanese chestnut (_Castanea crenata_) flowers reported in other studies [7; 18]. In _C. crenata_, acetophenone and styrene were some of the main VOCs of the flowers. Acetophenone and its derivatives are the characteristic components of the _C. crenata_ floral fragrance [18]. The volatile substances in the flowers of plants such as honeysuckle, chrysanthemum, peony, and dendrobium have the effects of killing bacteria, inhibiting bacteria, and deterring pests. Chestnut flowers have both excellent antioxidant and antimicrobial properties and have been used to make deworming, antibacterial, and medicinal products [9; 24; 25; 26]. Among the major volatile components of chestnut flowers identified in this study, \(\beta\)-pinene has been shown to have mosquito repellent, expecorant, and antitussive effects [27; 28; 29]. Acetophenone can be used to synthesize some analgesic, antiviral, anticancer, and antidepressant drugs [30]. Styrene is genotoxic, and styrene oxide--the major in vivo metabolite of styrene--is listed as a possible carcinogen [31; 32]. However, the hazards of styrene to insects are not known. Our results imply that \(\beta\)-pinene and acetophenone may be the main components of chestnut flower responsible for its anthelmittic, antibacterial, and medical properties. The species and contents of volatiles in flowers vary with the plant species and flower development stages [15; 33]. There are usually many kinds of VOCs in flowers in full bloom, and large amounts of volatiles are released [34]. There were 325 differential metabolites  
Figure 5: The expression analysis of acetophenone and styrene biosynthesis genes. Styrene and acetophenone in red mean the content of the two VOCs increased at FFS stage. between chestnut flowers in the FFS and IFS. These differential VOCs were significantly enriched in sesquiterpenoid and triterpenoid biosynthesis and ethylbenzene metabolism pathways.