ICP-MS analysis

The process of A. thaliana elemental analysis via inductively coupled plasma mass spectrometry (ICP-MS) has been described previously [33]. Briefly, different tissues, including flowers, whole stems and rosette leaves, from five-week-old plants treated twice with 100 mM NaCl or from untreated plants were cut with a scalpel while holding the plants with plastic tweezers. The collected tissues were rinsed with four times with 18-MΩ water in a 1000-mL breaker to wash off the impurities. Then, the rinsed samples were placed into a glass tube, and the samples were shifted to the bottom of the tube, making sure that no samples were left on the tube wall. The tubes were transferred to an oven at 65°C for 12 h. After cooling, twelve samples were weighed out on an analytical balance. All the samples, including the blank controls, were digested with 1 mL of concentrated nitric acid containing an indium (In) internal standard at 115°Cfor 4 h, and then the digested samples were diluted to 10 mL with 18 MΩ water. Elemental analysis for Li, B, Na, Mg, P, S, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Mo, and Cd was performed using an ICP-MS (NexION 350D; PerkinElmer) coupled to an Apex desolvation system and an SC-4 DX auto sampler (Elemental Scientific Inc., Omaha, NE, US). All samples were normalized to calculate weight, as determined using a heuristic algorithm using the best-measured elements, the weights of the eight weighed samples, and the solution concentrations, as previously described.