*3.8. Extraction of Volatile Organic Compounds*

The volatile organic compounds (VOCs) of 16 plants per treatment and replication (*n* = 64) were extracted according to the following procedure: 100 mg (±2%) of gently ovendried and powdered (3 intervals of 10 s at 15,000 rpm via Tube Mill control, IKA®, Staufen, Germany) thyme leaves were transferred into 2 mL screw cap micro tubes (SARSTEDT AG & Co. KG, Nümbrecht, Germany) including two steal grinding balls (Ø 2 mm). The plant material was homogenized in 1.0 mL of isooctane (containing 1:40,000 (*v*/*v*) 6-methyl-5 penten-2-one as internal standard) for 10 min at 30 rps with a ball mill (MM400, Retsch®, Haan, Germany). After 10 min of ultra-sonication (Sonorex RK 106, BANDELIN electronic GmbH & Co. KG, Berlin, Germany) and 10 min of centrifugation at 13,000 rpm (Heraeus™ Labofuge™ 400 R, Thermo Scientific™, Osterode, Germany) at 22 ◦C respectively, the supernatants were transferred into GC-vials and stored at −70 ◦C until analysis.
