## 2 Results and Discussion
### Changes of Volatile Components with Daily Rhythm  
Table 2 shows that the volatile components changed with the daily rhythm. The total relative content is expressed in total peak areas. The odor was strongest at 12:00, with a total peak area of 5117, followed by 4555 at 10:00, and it gradually declined until 18:00-04:00, with the lowest values of 535-640, and then rose again at 8:00 with a peak area of 1917. These results were similar to those reported for _[PERSON]_. [PERSON]'s Pacific Sunset and Gongora bufonia, which showed stronger odor levels at 09:00-13:00 and 10:00, respectively [8; 22]. Orchids possess entomophilous flowers, and the aroma volatile components are key for the attraction of insects. Flowers emit different volatile compositions at different times to attract specific pollinators, such as a specific type of bee or diurnal/nocturnal insects [23; 24]. The diurnal bee is a pollinator for both Phalaenopsis and Gongora bufonia; therefore, the strongest odor emitted was during the day.  
There were significant differences in the emission of most single compounds. The exceptions were tiglaldehyde, 2-methyl-2-buten-1-ol, benzaldehyde, \(\beta\)-myrcene, 2-ethylhexanol, methyl salicylate, 2-ethylhexyl acrylate, \(\beta\)-citral, \(\beta\)-caryophyllene, (Z)-\(\beta\)-farnesene, benzyl tiglate, and nerolidol, for which no obvious differences in relative percentage of floral scent emitted over a daily rhythm were found. Linalool had the highest relative percentage change, with a maximum of 37.09-35.8% at 10:00-12:00 and a minimum of 4.72% at 22:00 (Table 2). Such changes were similar to the total relative content changes over the daily rhythm. We note that [PERSON] et al. [25] studied linalool as a mate attractant component in the male bee. Not all the volatile compositions peaked during the day, as the relative percentages of \(\beta\)-pinene, limonene, (_E_)-4,8-dimethyl-l,3,7-nonatriene, menthol, tridecane, and copaene were highest at 18:00-22:00. The emission of _cis_-linalool oxide, \(\alpha\)-terpineol, isopentyl benzoate, and 2-methylpropanoate peaked at nightfall (16:00-18:00; Table 2). [PERSON] et al. [23] suggested that changes in aroma components during the daily rhythm of _Silene otites_ may attract specific insects at different times, not only the originally identified moths and mosquitoes. This may explain why some volatile components were highest at nightfall or nighttime for _Onc_. Rosy Sunset. It is worth noting that (_E_)-4,8-dimethyl-l,3,7-nonatriene, which is generally emitted from the damaged leaves and attracts insects, is only found in a few flowers, such as _Magnolia_ taxa and _Liriodendron tulipifera_[26]. In our results, (_E_)-4,8-dimethyl-l,3,7-nonatriene was emitted in highest concentrations at nighttime,  
Figure 1: Total ion chromatogram of volatile components of _Onc_. Rosy Sunset (peak numbering in accordance with numbering in Table 1; x, column, or septum bleed). (**A**) Original total ion chromatogram; (**B**) Normalized total ion chromatogram.  
although it is not known whether this is related to the attraction of nocturnal insects. Linalool was a primary component of emission, over all times of the daily rhythm.  
In terms of horticultural characteristics, the finding that the _Onc._ Rosy Sunset odor was strongest in the morning can be used to market the flowers to consumers and as a reference for hybrid offspring selection time. In addition, the selection of parent plants that emit aroma during the afternoon or nightfall can be used in breeding programs with _Onc._ Rosy Sunset to breed new _Oncidium_ cultivars that emit aroma all day.