4.6. Extraction and Quantification of Phytohormones Using LC–MS/MS

The extraction procedure and phytohormone determination was carried out according to Müller et al. (2022) [39]. The tissue was extracted and homogenized in 1.5 mL methanol containing 60 ng D4-SA (Santa Cruz Biotechnology, Santa Cruz, CA, USA), 60 ng D6-JA (HPC Standards GmbH, Borsdorf, Germany), 60 ng D6-ABA (Toronto Research Chemicals, Toronto, ON, Canada) and 12 ng D6-JA-Ile (HPC Standards GmbH, Borsdorf, Germany) as the internal standards. Phytohormone analysis was performed using LC–MS/MS on an Agilent 1260 series HPLC system (Agilent Technologies, Santa Clara, CA, USA) coupled to a tandem mass spectrometer QTRAP 6500 (SCIEX, Darmstadt, Germany).