2.2. Preparation of aqueous chlorine dioxide
Aqueous ClO2 was prepared by combining 25 g of sodium chlorite (technical grade 80%; SigmaeAldrich, St. Louis, MO, USA) and 7 ml of 1 N hydrochloric acid with 300 ml of DW and shaking on a rotary shaker at 150 rpm at 21 ± 2 C for 1 h. The ClO2 solution was diluted with sterile DW to give a concentration of 200 mg/ml immediately before treating seeds. The concentration of ClO2 was measured using a chlorine colorimeter (model Dr/820; Hach, Loveland, CO, USA).