Rhizosphere volatiles were trapped through passive diffusion by placing one Tenax® (Markes International, Llantrisant, United Kingdom) trap containing 200 mg Tenax/tube type TA 60/80trap inside a metal holder in each pot, reaching an approximate depth of 5 cm. Metal holders were stainless steel cylinders with perforations allowing the air entrance while protecting the trap from soil contamination. Tenax traps were placed before the onset of the herbivory stress for 24 h (T0). Upon the leaf-herbivory stress induced by S. exigua, new Tenax traps were placed in the same pots where T0 was measured. Traps were placed 24 h after the onset of the herbivory stress for a 24 h period, thus collecting the volatiles during the initial 24–48 h herbivory stress induction period (T1). Traps were tightly closed and stored at room temperature until measurement. Before utilization, Tenax traps were preconditioned by heating at 300°C for 45 min under helium flow (5 l/min).
Full details of Tenax measurement regarding thermal desorption, GC/Q-TOF measuring conditions, calibration, data analysis, and compound identification are described by Lee Díaz et al. (2022 (link)). Briefly, volatiles was thermo-desorbed from Tenax traps at 240°C for 8 min and then transferred to an ultra-inter column (122–5532 UI, Agilent Technologies, Inc., Santa Clara, CA, USA) of the GC/Q-TOF (model Agilent 7890B GC and the Agilent 7200A Q-TOF). An n-alkane (C8–C20) standard solution was spiked at the beginning of the run for calibration. Mass spectra of compounds were acquired in full-scan-mode and GC/Q-TOF raw data was translated to .cdf format and analyzed with MzMine v2.53 (Pluskal et al. 2010 , 2020 ) for mass feature detection and peak intensity quantification. Parameters used for GC-MS peak intensity tables (Du et al. 2020 ) are available inTable S3 (Supporting Information ). Peak intensity tables were used in combination with chromatogram data (Mass Hunter Qualitative v10, Agilent Technologies) for manual identification of volatile compounds comparing the mass spectrum of target compounds with the NIST 2020 database (V2.20, National Institute of Standards and Technology, USA).
Full details of Tenax measurement regarding thermal desorption, GC/Q-TOF measuring conditions, calibration, data analysis, and compound identification are described by Lee Díaz et al. (2022 (link)). Briefly, volatiles was thermo-desorbed from Tenax traps at 240°C for 8 min and then transferred to an ultra-inter column (122–5532 UI, Agilent Technologies, Inc., Santa Clara, CA, USA) of the GC/Q-TOF (model Agilent 7890B GC and the Agilent 7200A Q-TOF). An n-alkane (C8–C20) standard solution was spiked at the beginning of the run for calibration. Mass spectra of compounds were acquired in full-scan-mode and GC/Q-TOF raw data was translated to .cdf format and analyzed with MzMine v2.53 (Pluskal et al. 2010 , 2020 ) for mass feature detection and peak intensity quantification. Parameters used for GC-MS peak intensity tables (Du et al. 2020 ) are available in
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