Deuterated standards

Analytical-grade reagents were used to determine the POD, CAT, SOD, MDA, proline, and chlorophyll levels (Sangon Biotech [Shanghai] Co., Ltd. or Solarbio Science and Technology [Shanghai] Co., Ltd.). All deuterated standards and calibration samples for determining the ABA, auxin, GA1, GA3, and GA7 levels were purchased from Sigma-Aldrich (St. Louis, MO, USA). Reagents for the high-performance liquid phase were sourced from Thermo Fisher Scientific Inc. Consumables such as petri dishes, agar, and sucrose for endophytic isolation and fermentation were purchased from Solarbio Science and Technology Co., Ltd. PDA, PDB, or water agar (WA) media were used. The PDB medium contained 200 g l⁻¹ potato and 20 g l⁻¹d-glucose. The PDA medium contained 200 g l⁻¹ potato, 20 g l⁻¹d-glucose and 15 g l⁻¹ agar. The WA medium was prepared by adding 10 g agar to 1000 ml distilled water.

Phenolic compounds standards were purchased from Extrasynthese (Genay, France) and Sigma-Aldrich (St. Louis, MO, USA). Carotenoid standards were purchased from Sigma-Aldrich. Deuterated standards were purchased from Sigma-Aldrich and Spectra2000. Solvents were purchased from AppliChem, Panreac Quimica SA (Barcelona, Spain), Sigma-Aldrich, and Trizol Reagent for RNA extraction was supplied by Fisher Scientific (Madrid, Spain) and the SYBR® Green assay for RT-PCR analysis by Bio-Rad Laboratories (Billerica, MA, USA) and primers were provided by IDT DNA Technologies (Leuven, Belgium). Ultra-pure water was produced by a Millipore system (Millipore, Bedford, MA, USA). More details are given in the Supplementary Materials S1.