4100 mpicp oes

After about 10 days of stress treatment, when the control leaves reached the three-leaf stage, the maize seedlings from each treatment were carefully removed from the nutrition bowl, the vermiculite attached to their roots was washed with water, and the roots, stems and leaves were separated with a double-sided blade. The tissue was placed in a 105°C oven for 30 min, and then baked at 80°C for 48 h. The contents of Na⁺, K⁺ and Ca²⁺ ions in roots, stems and leaves were determined using a 4100-MPICP-OES (Agilent, Santa Clara, CA, USA) [22 (link)].

Roots and shoots were dried at 80 °C to a constant weight for 24 h. The dry weights of the samples were measured. The dried roots and shoots were incinerated in a muffle furnace at 300 °C for 3 h and 575 °C for 6 h. The ashes were dissolved in 10 cm³ 5% nitric acid and diluted with 5% nitric acid accordingly. The concentrations of macroelements (Na, K, Ca, and Mg) and microelements (Cu, Fe, Mn, and Zn) in the digested solution were determined using a 4100-MP ICP-OES (Agilent, Santa Clara, CA, USA) [89 (link)]. Three biological replicates were tested.
Proline contents in fresh plant tissues were measured using the AccQ-Tag derivatization kit (Waters, Milford, MA, USA) with LC-MS, and three biological replicates were examined. In brief, 20 mg lyophilized plant tissue powder was extracted with 1 cm³ water under sonication. The extract was derivatized with the Waters AccQ-Tag amino acid derivatization kit and analyzed with LC-MS [90 (link)].
H₂O₂ contents were measured using the Amplex Red Hydrogen Peroxide/Peroxidase Assay Kit (Thermo Scientific, Waltham, MA, USA) according to manufacturer’s instructions. Each sample was subjected to three biological replicates and two technical replicates.