Metabolite measurements
The same pooled plant materials used for RNA extraction were used to determine ion contents, membrane lipids, and primary metabolites. For cation/anion analysis, 20 mg frozen, powdered shoot or root material was transferred into a reaction tube, suspended in 500 µl of Milli-Q water by vortexing, and centrifuged for 1 min at 13,000 g. The supernatant was transferred to a new reaction tube and the pellet re-extracted using the same procedure. First and second supernatants were combined before filtering through a 0.45 µm membrane. Ion chromatographic separation was achieved on a Thermo Scientific ICS-5000 IC system (Thermo Fisher Scientific, USA) using a Dionex CS12A , Ion Pac (2 × 250 mm) analytical column with a AG12A guard column (2 x 50 mm). Quantification was achieved using Chromeleon 7.2 version SR4 software. Standard curves were prepared using dilution of the following standards, for anions Thermo Scientific Dionex Seven Anion Standard II, and for cations Thermo Scientific Dionex Six Cation II Standard. Lipid extraction followed the procedure described by Vu et al. (2014) and non-polar metabolites for gas chromatography-mass spectrometry (GC-MS) analysis were extracted from powdered, freeze-dried materials using the protocol described by Broeckling et al. (2005).