Tolerance and Cr Transport Characteristics of Neyraudia reynaudiana Under Cr(VI) Stress

Hexavalent chromium Cr(VI) contamination poses a significant risk to soil ecosystems because of its high mobility and toxicity. Identifying plant species capable of surviving under Cr stress and translocating Cr to harvestable aboveground tissues is a key step in developing phytoremediation strategies. Chromium (Cr) contamination, particularly hexavalent chromium Cr(VI), poses a substantial risk to soil ecosystems. This study evaluated the tolerance, Cr distribution, and antioxidant responses of Neyraudia reynaudiana grown in soil amended with K2Cr2O7. Seedlings were exposed to five nominal Cr treatments (200, 400, 600, 800, and 1000 mg kg−1) and sampled at 30, 60, 90, 120, and 150 days. Total Cr concentrations were determined in soil, roots, and shoots; translocation factor (TF) and shoot bioconcentration factor (BCF) were calculated. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were also measured. N. reynaudiana remained viable throughout the 150 d exposure period, including under the highest nominal Cr treatment. At 150 d, TF exceeded 1.0 in the Cr400–Cr1000 treatments and reached a maximum of 1.50 in the Cr600 treatment, indicating substantial root-to-shoot Cr translocation under these conditions. In contrast, shoot BCF values remained below 0.30 (0.20–0.29 at 150 d), indicating limited concentration-based Cr enrichment in aboveground tissues. Soil total Cr concentrations declined during cultivation; however, biomass-based Cr mass balance is required to quantify net plant-associated Cr removal. The activities of SOD, POD, CAT, APX, and GR showed distinct Cr-concentration- and growth-stage-dependent responses, with the overall antioxidant response generally strongest at intermediate Cr concentrations and attenuated under the highest treatment. These findings indicate that N. reynaudiana has tolerance to Cr(VI) stress and the capacity for root-to-shoot Cr translocation in a controlled pot experiment. Its practical phytoremediation efficiency requires further evaluation using biomass-based Cr accumulation, Cr speciation, and field validation. By characterizing the Cr tolerance and translocation responses of a native slope-restoration species, this study provides a physiological basis for evaluating N. reynaudiana as a candidate plant for integrated stabilization and phytoextraction-oriented remediation strategies at Cr-contaminated sites. It also identifies the key evidence needed to translate pot-scale responses into reliable site-specific remediation assessments.