Varying concentrations of soil chromium (VI) for the exploration of tolerance thresholds and phytoremediation potential of the oregano (Origanum vulgare)
2019
Levizou, Efi | Zanni, Anna A. | Antoniadis, Vasileios
Varying concentrations of soil Cr(VI) were used in order to explore the tolerance thresholds and phytoremediation potential of Greek oregano (Origanum vulgare), in a pot experiment conducted outdoors. Oregano exhibited a rather exceptional capacity to bioaccumulate Cr in both the aerial part (up to 1200 mg of total Cr kg⁻¹ DM) and the root—reaching 4300 mg kg⁻¹ DM when grown in soil [Cr(VI)] of 150–200 mg kg⁻¹. Plant responses indicated that there was a threshold set at 100 mg Cr(VI) kg⁻¹ in the soil, above which the following results were recorded: (i) a restriction of Cr translocation from below- to above-ground plant part, (ii) a raise of the soil-to-root Cr transfer, and (iii) the Cr(III) evolution from the reduction of Cr(VI) was significantly decelerated in the root and accelerated in the aerial part. Soil [Cr] that surpassed this threshold challenged plant tolerance, resulting in a dose-dependent reduction of growth and antioxidant phenolics pool. Nonetheless, the significant Cr uptake capacity at plant level accounted for the considerably short remediation time (i.e., 29 years at soil [Cr(VI)] of 150 mg kg⁻¹) calculated according to these results. The overall performance of oregano indicated that phytoremediation would be feasible at sites with Cr contamination levels ranging within the above-defined thresholds.
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