## 2 Results
### Gene Expression Analysis  
The qRT-PCR method measured and compared the relative expression levels of 13 genes involved in floral color and scent biosynthesis at two key stages of flower development when scent emission occurs: budding and open-flower. The genes were _PAR_, _GPS_, _GGPPS_, _PAL_, _DXR_, _DXS_, _LIS_, _CCD1_, _AAT1_, _ANS_, _FLS_, _CER1_, and _RhMYB1_. Figure 5 shows the expression patterns of these genes at different stages. White flowers had higher expression levels of all main genes at the budding stage than at the open-flower stage. The expression profiles of these genes gradually decreased as the flowers opened. Seven genes (_GPS_, _GGPPS_, _DXR_, _DXS_, _LIS_, _CCD1_, and _AAT1_) related to floral terpene volatile compound biosynthesis showed similar expression trends. Among them, _GGPS_ had the highest expression level in white floral buds (121.38-fold), followed by _CCD1_ (29.18-fold), _DXR_ (17.06-fold), _DXS_ (16.19-fold), and _GPS_ (14.49-fold). Except for _FLS_, _DXS_, _LIS_, and _PAR_, the other genes in white flowers had significant differences in expression levels among different stages. Figure 4: Total Ion Chromatograms of _R. canina_ petals in positive and negative modes. The figure shows the chromatograms of white (**a,c**) and dark pink (**b,d**) petals in positive (**a,b**) and negative (**c,d**) modes, respectively. The peaks correspond to the compounds detected in the petals. The compounds are as follows: 1: Quercetin-3-O-rutinoside-7-O-glucose, 2: Dihydroxy-dimethoxy flavone, 3: Gallic acid, 4: Cyanidin, 5: Quercetin-3-O-hexoside, 6: Kaempfer-3-O-rutinoside, 7: Kaempfer 3-O-(6′′-malonyl-glucoside), 8: Tetra-O-galloyl-hexoside, 9: Myricetin, 10: Ellagic acid, and 11: Kaempfer-3-O-glucose. Dark pink petals had higher expression levels of the _ANS_ gene, which participates in anthocyanin synthesis, than white petals. The expression of _ANS_ and _CCD1_ differed significantly in dark pink petals, while the other genes did not. The _ANS_ gene had remarkably higher expression levels at white flower buds (8.50-fold) than at dark pink flower buds, followed by the _FLS_ gene (1.55-fold). The _FLS_ gene, which is the key gene for flavonoid synthesis, had higher expression levels at the budding stage (1.77-fold) than at the open-flower stage in dark pink flowers. The _ANS_ gene had the opposite trend: it had higher expression levels at the open-flower stage than at the budding stage in dark pink flowers. The _FLS_ gene catalyzes flavanol biosynthesis, which peaks in the early stages of flower development before anthocyanin accumulation. The _ANS_ gene catalyzes anthocyanin formation, such as pelargonidin and cyanidin. Figure 5: _Cont._  
Figure 5: Relative expression of main genes which are involved in flower color and scent biosynthesis in rose flower. Different flower developmental stages including budding stage (S1) and open-flower stage (S2) was selected for this assay. The fold change expression was calculated after normalization to the beta-actin gene. The open-flower stage (S2) was selected as a reference for white and dark pink petals. Standard errors are indicated by vertical bars. The values of error bars are revealed mean \(\pm\) SE, \(n\) = 3. Different letters (a and b) indicate significant differences at \(p\) < 0.05 between S1 and S2 for each petal color, as determined by one-way ANOVA and Duncan’s test. In white petals, the expression of the _ANS_ and _PAL_ genes, which are related to anthocyanin biosynthesis, was the highest at the budding stage. In dark pink petals, the expression levels of _PAL_ and _PAR_ genes, which are also related to anthocyanin biosynthesis, were lower at the budding stage than at the open-flower stage. The _PAR_ gene had the highest expression level (251.31-folds) at the budding stage of white flowers, followed by the _PAL_ gene (12.38-folds). The _CER1_ gene, which is involved in long-chain alkane synthesis in epidermal parts of flower petals, had higher expression levels in white flower buds (5.63-folds) than in dark pink flower buds.