Headspace collection and gas chromatography-mass spectrometry (GC-MS) analysis

The volatile compounds were collected using a headspace-solid phase microextraction (HS-SPME)/GC-MS method. The whole flower was sealed in a 20-mL extraction bottle and equilibrated at 50°C for 10 min. The volatile compounds were extracted and adsorbed for 30 min using an SPME fiber [polydimethylsiloxane (PDMS), diameter 65 μm]. Then, the trapped floral scent compounds were analyzed using a Shimadzu GCMS-TQ8040 system. An Rxi-5Sil MS capillary column (30 m × 0.25 mm × 0.25 μm) was used for the separation of volatile compounds with helium as the carrier gas, at a flow rate of 1 mL/min. The column operating conditions were as follows: an initial 50°C hold step for 2 min, followed by an increase to 170°C at a rate of 4°C/min (held for 1 min), then to 270°C at a rate of 20°C/min, and a final hold step for 2 min. The volatiles were identified by comparing the mass spectra and retention times with authentic standards.