## 3 Discussion  
### Differences in Floral Components of N. 'Eldorado' at Different Flowering Stages  
The volatile compounds from flowers are rather complex, and they are affected by different blossom periods [(29)]. The analysis of VOCs in the flowers of _Nymphaea_ L., one of the basic groups of angiosperms, can provide basic data for the study of coevolution between floral and pollinating animals [(30)]. From the HS-SPME/GC-MS analysis, a total of 60 compounds were detected in the petals of \(N\). 'Eldorado' at different flowering stages, and 27 compounds were present at all four flowering stages. The types and total relative contents of VOCs decreased in the following order: full-flowering stage > initial-flowering stage > bud stage > end-flowering stage, indicating that the types and relative contents of VOCs at the full-flowering stage were higher. In most plants (such as citrus flowers [(38)],  
Figure 8: Scanning electron microscopy (SEM, **A**) images and transmission electron microscopy (TEM, **B**) images of \(N\). 'Eldorado’ flower petals at different flowering stages. Arrows in (**A**) represent papillae on the epidermis of flower petals. V—vacuole, CW—cell wall, P—plastids, S—starch granules, MG—Osmophilic matrix granules. Cananga adorata_[39], and _Ocimum citridorum_[40]), the release of VOCs and its diversity are lower at the bud stage and increase sharply at the blooming stage, then VOCs decline sharply after entering the final flowering stage. For example, more hydrocarbon, esters, and alcohol compounds were detected at the full-flowering stage than at the other flower stages of _C. adorata_; the total number of VOCs at the wilted-flowering stage decreased by nearly half of that at full-flowering stage [40]. These results were similar to those of our study. However, the amount of scent emission and the diversity of floral volatiles were greatest at the initial-flowering stage of _Luculia yumanensis_[41], which was different from the results of the present study. Our research of the VOCs of \(N\). 'Eldorado' at different flowering stages includes alkenes, alcohols, esters, aldehydes, ketones, and alkanes, among which the proportions of alkenes and alkanes are the highest. [PERSON] et al. [29] found the main volatiles from _N. Caerulea_ flower at the early stage of the blossom period were 6,9-heptadecadiene (40.1%), pentadecane(15.5%), 8-heptadecene (15.3%), benzyl acetate (10.4%), and benzyl alcohol (4.4%), which were four common major compounds under different flowering periods. However, in our research, benzyl acetate (12.15%), benzaldehyde (5.78%), and benzyl alcohol (23.43%) reached their highest levels at full-flowering stage; only (E6,E9)-heptadecadiene (6.82%) and cis-\(\alpha\)-farnesene (5.11%) were higher at the initial-flowering stage than at the other stages. Other studies have shown that there were no marked differences in floral scent composition between the pistillate (day 1) and staminate phases (day 2) of the flower-blooming period in seven species of _Nymphaea_ subg. _Hydrocallis_ (Nymphaeaceae), with the exception of _N. rudgeana_, in which the emission of (methoxymethyl)benzene was dramatically reduced during the staminate phase, and floral scent discharge was greater in the pistillate phase than in the staminate phase [30]. [PERSON] et al. [33] analyzed the chemical compositions of four kinds of _N. hybrid_, and found that the major volatile components were benzyl alcohol, pentadecane, trans-\(\alpha\)-bergamotene, (E)-\(\beta\)-farnesene, and (E6,E9)-heptadecadiene, which released the sweeter fruity floral scent. Previous studies found that the main VOCs in tropical water lilies were benzyl alcohol, benzyl acetate, 6(E),8(E)-heptadecadiene, 6,9-heptadecadiene, pentadecane, 8-heptadecene, trans-\(\beta\)-farnesene, and Z,Z-10,12-hexadecialen, while pentadecane, undecane, cis-ocimene, tridecane, 8-heptadecene, 6,9-heptadecadiene, and tetradecane were the major VOCs in hardly water lilies [32; 42]. The main floral scent components at different flowering stages of \(N\).