Model 6890 n gas chromatograph

GC-MS analysis of the methyl ester and pyrrolidine derivatives allowed identifiying the fatty acids present in each fraction. The analyses were performed on a model 6890N gas chromatograph (Agilent, USA) coupled to a model 5973N mass selective detector (Agilent, USA), on a DB-5MS column, using helium as carrier gas. The injection volume was 0.2 μL and temperatures of 175 °C and 250 °C were used for the injector and detector, respectively. The oven was programmed in three steps: it was started at a temperature of 50 °C for 1 min, then increased at a rate of 5 °C/min to 150 °C, where it remained for 3 min, and then increased at 10 °C/min to 300 °C and held for 16 min.
The mass spectra were compared with the NIST02.L and NIST5a.L databases and the information was generated with MSD ChemStation software. The relative abundance of the fatty acids was calculated with the area under the curve of each chromatographic peak of the methyl ester derivatives. Each analysis was performed in triplicate.

Terpenes were extracted and quantified according to Flø et al. (2018 (link)) from bark samples collected 3 h, 24 h, 1 week and 4 weeks after treatment with water or MeJA. Briefly, ground bark tissue was extracted overnight with hexane containing 10 μg/ml pentadecane as an internal standard. The supernatant was removed for analysis by GC‐MS using a model 6890 N gas chromatograph (Agilent Technologies) connected to a model 5973 mass spectrometer (Agilent Technologies) fitted with an autosampler. Remaining bark tissue was dried at room temperature for 3 days and weighed to determine dry weight. Terpenes were identified using a library of standards. Terpene concentrations were determined by normalising to the internal standard and correcting for dry weight. As the terpene data were non‐parametric and could not be normalised by transforming the data, Aligned Ranks Transformation ANOVA was used to determine significant differences between treatments over time.