Irm ea ms

For each harvest, all plant compartments (root, nodule, leaf, stem) were dried for 48 h in an oven at 80°C. The biomass of each part was measured and then dried tissues were ground into a fine powder. Aliquots were analyzed for their C and N concentrations with an elemental analyzer (EA, VarioMicroCube, Elementar) and their ¹³C and ¹⁵N enrichment determined with an online isotope ratio mass spectrometer (irm-EA/MS, Isoprime/Elementar).

δ¹³C was measured according to the methodology published by Guyon et al. (2015 (link)). Analyses were carried out using an elemental analyzer (EA, VarioMicroCube, Elementar, F-69623 Villeurbanne, France) coupled to a mass spectrometer for isotope ratio monitoring (irm-EA/MS, Isoprime/Elementar, F-69623 Villeurbanne, France). Ten μL wine samples were poured into tin capsules and injected into the oxidation tube (950°C) under helium (200 mL/min) and oxygen (30 mL/min) flux, at a reduction furnace temperature of 550°C. Combustion gases were dried and eluted on a specific column that physically retains the CO₂ (60°C) and then releases it when the temperature is increased (210°C). An open split system was used to regulate gas withdrawal to the irm-MS and the current trap was set at 200 μA. The overall measurement duration was 600 s.