Cp 3800 apparatus

The GC/EI-MS analyses were performed with a CP-3800 apparatus (Varian Inc., Palo Alto, CA, USA) equipped with a DB-5 capillary column (30 m × 0.25 mm i.d., film thickness 0.25 μm) and a Varian Saturn 2000 ion-trap mass detector (Varian Inc., Palo Alto, CA, USA). The oven temperature was programmed rising from 60 °C to 240 °C at 3 °C/min; injector temperature, 220 °C; transfer-line temperature, 240 °C; carrier gas, He (1 mL/min). The acquisition parameters were as follows: full scan; scan range: 35–300 m/z; scan time: 1.0 s; threshold: 1 count. The identification of the constituents was based on the comparison of their retention times (t_R) with those of pure reference samples and their linear retention indices (LRIs) determined relatively to the t_R of a series of n-alkanes. The mass spectra were compared to those listed in the commercial libraries NIST 14 and ADAMS and in a homemade mass-spectral library built up from pure substances and components of known oils, and MS literature data [39 (link),40 ,41 (link),42 ,43 ,44 ].

Fresh flowers were transferred and stored in glass containers (ø 4.5 mm, h 80 mm) to avoid plastic volatile contamination. The spontaneous emission profiles of the studied flowers were analyzed using the method described in a previous study (Demasi et al., 2019 (link)). Volatiles were sampled from the flower of each species with a solid phase microextraction device (SPME, Supelco, Bellefonte, PA, United States) coated with polydimethylsiloxane (PDMS, 100 μm coating thickness, St. Louis, MO, United States). Then, they were injected into a Varian CP-3800 apparatus (Varian Inc., Palo Alto, Santa Clara, CA, United States) with a DB-5 capillary column (30 m × 0.25 μm i.d. film thickness 0.25 μm) coupled to a Varian Saturn 2000 (Varian Inc., Palo Alto, Santa Clara, CA, United States) ion-trap mass detector for the gas chromatography–mass spectrometry (GC-MS) analyses. The identification of constituents was based on the comparison of the retention times (Rt) with those of pure reference samples and their linear retention indices (LRIs) determined relatively to a series of n-alkanes. The mass spectra were compared with those listed in the known commercial libraries (NIST, 2014 ; Adams, 2007 ) and in a homemade mass spectra library built up from pure substances and components of known essential oils and MS literature data.

Emitted volatiles were analyzed using a Supelco (Bellofonte, USA) SPME device coated with polydimethylsiloxane (PDMS, 100 μm) in order to sample the headspace of each living/flowering plant. Plants of StuM population did not bloom, thus data on VOCs concerned eight populations, for a total of 33 plants. Sample was introduced individually into a 30 ml glass conical flask and allowed to equilibrate for 30 min. After the equilibration time, the fiber was exposed to the headspace for 15 min at room temperature; once sampling was finished, the fiber was withdrawn into the needle and transferred to the injector of the GC system, where the fiber was desorbed. GC-FID and GC-MS analyses were performed according to Pistelli et al. (2017 (link)) using a Varian CP-3800 apparatus (Paolo Alto, California, USA) equipped with a DB-5 capillary column (30 m × 0.25 mm i.d., film thickness 0.25 μm) and a Varian Saturn 2000 ion-trap mass detector. The oven temperature was programmed rising from 60°C to 240°C at 3°C/min; injector temperature, 220°C; transfer-line temperature, 240°C; carrier gas, He (1 ml/min).