Physiological, Ultrastructural, and Antioxidant Modulation in Response to Nickel and Chromium Induced Oxidative Stress and Their Accumulation in Oxalis corniculata L.

The present study was conducted to investigate the growth performance, physiology, leaf epidermis ultra-structure, metal accumulation, and antioxidant properties of Oxalis corniculata grown in soil contaminated with nickel (Ni) and chromium (Cr). The different levels of nickel (Ni10, Ni20, Ni40, and Ni50 mg/kg soil) and chromium (Cr10, Cr15, Cr30, and Cr40 mg/kg soil) were administered to the soil 15 days after sowing (DAS), i.e., two-leaf stage of the test plants. The sampling was done 60 and 90 days after sowing (DAS). Low levels of both metals (Ni10 and 20 and Cr10) enhanced growth, caused no abnormality in leaf epidermis structure, and slightly decreased the activity of antioxidant enzymes and the proline content. Ni40–50 and Cr15–40 application caused a considerable and significant decline in growth characteristics and activity of nitrate reductase. Ultra-structural abnormalities of the leaf epidermis were also observed. Higher Ni and Cr levels increased the activity of superoxide dismutase, peroxidases, and catalase and proline content manyfold. Cr was found to be more toxic than Ni. Translocation factor (TF) values for Ni (1.023) and Cr (0.934) indicated that Ni was more efficiently transferred from root to shoot. Possible implications of these findings for community dynamics, ecosystem functions, and ecosystem services are also discussed.