Determination of Mn and Cr in Plants

To determine the Mn and Cr content of root stems and leaves, 0.5 g of plant samples was added to a solution containing 2 mL of HNO₃ (67% w/v) and 2 mL of H₂O₂ (30% v/v). The resulting solution was then added to a mixture containing 10% (v/v) HCl, 10% KI (w/v), and 5% ascorbic acid (w/v). In the final step, a Shimadzu AA-6200 atomic absorption spectrometer (HG-AAS), was utilized to determine the accumulation of Mn and Cr using an external standard [105 (link)]. The accumulation of nitric oxide was detected by converting the oxygen–hemoglobin content to methemoglobin. Thus, in this approach, 0.5 g of root, stem, and leaf samples were added to a mixture containing sodium acetate (0.1 M), 3 mL of buffer (pH 6.0), 1 M NaCl, and 1% (w/v) ascorbic acid. It was then centrifuged for 25 minutes at 7000× g at 5 °C [106 (link),107 (link)].