## 1 Introduction  
Floral scents are composed of volatile organic compounds (VOCs) with low relative molecular masses, such as terpenoids, phenylpropanoids/benzenoids, and fatty acid derivatives, and include some compounds containing nitrogen or sulfur [1; 2]. Floral VOCs have important sensory and aesthetic value in ornamental plants and play a role in attracting insects to ensure pollination and fruiting in all floral plants in general [3]. When plants are invaded by foreign organisms, VOCs can be used to attract their natural enemies and to implement other plant defenses [4; 5]. Floral VOC composition, relative VOC content, and VOC release differ among species and varieties, and even within the same variety at different growth stages and environments [6; 7]. Research on the floral VOCs of ornamental plants has received extensive attention, mainly involving the identification of plant VOCs, the analysis of the main components of floral scent, and the influence of VOCs on insect pollination behavior [8; 9]. In plants, more than 1000 floral volatile compounds have been identified, covering more than 60 families [10]. The common floral scent components found in many plants are lanalool, benzyl alcohol, benzaldehyde, ocimene, and benzyl alcohol [11]. The volatile components of the flowers of many ornamental plants, such as _Rosa rugosa_[12], _Lilium_ spp. [13], and _Orchidae_ spp. [14], have been studied in detail. However, there have been few studies on VOCs from water lilies, a well-known aquatic flowering plant. With the development of molecular biology, the anabolic pathway of floral compounds has been gradually explored, as well as several new methods for the genetic improvement of plant floral fragrances [15; 16]. There were differences in the types and amounts of VOCs released by different plants during the flowering period. Research has shown that the total volatile content in _Lilium_ spp. flowers at the full flowering stage was higher than that at the initial flowering stage, with a high content of lanalool, (Z)-\(\beta\)-basil, 1,8-cineole, (+) limonene, laurene, methyl benzoate, etc. [17; 18]. The release of VOCs from the flowers of _Jassminum sambac_ were generally higher at the full-flowering stage, and \(\alpha\)-farnesene, lanalool, and benzyl acetate were most abundant in the flowers [19]. _Plualenopsis bellina_ had the highest number of volatiles during the morning and full bloom, with 29.82% monoterpene and 23.33% sesquiterpenes in total [20]. In addition, the content and composition of volatile components in plants are closely related to the flower parts [21]. The relative content of alkanes in the stames of peony plants is much higher than that in the whole flower and in petals, so stames may be important sites of alkane synthesis [22]. Other studies have shown that the secretion from flowers is also related to their cell structure. In petals, the fragrance is usually released by diffusion through the entire epidermal cell. For example, the release of fragrance in fragrant plants such as _Styrax tonkinensis_[23] and _Optishopappus taihangensis_[24] is related to the cell structure of their petals, especially the epidermal cell structure. Glandular trichomes (GTs) are the main organs responsible for the emission of volatiles. _Nymphaea_ L. is a perennial aquatic herb belonging to the _Nymphaea_ family, which can be divided into tropical water lilies and hardy water lilies [25]. There are more than 50 species (including varieties) of water lilies worldwide, mainly distributed in tropical, subtropical, and temperate areas [26]. They are widely used in food processing, spice development, garden greening, and other applications [27; 28]. The floral scent is one of the most important ornamental traits of water lilies, and its composition and content differ among varieties. At present, compared with the characteristics that are easy to observe, such as flower color, research on _Nymphaea_ floral scents has focused mainly on the analysis of the VOCs of different _Nymphaea_ spp.