This study investigated the enhancing effects of soil treatment with ethylene diamine tetraacetic acid (EDTA) and oxalic acid (OA) on the remediation of Cr(VI) contaminated soil by Datura stramonium L. A greenhouse pot experiment was conducted, where Cr(VI) contaminated soil was treated with 100 mg/kg Cr(VI) and varying concentrations of EDTA (5 and 10 mmol/kg) and OA (5 and 10 mmol/kg). The effects of these soil treatments on biomass, chlorophyll content, antioxidant enzyme activities, and Cr(VI) enrichment and translocation efficiency of D. stramonium were evaluated. The results showed that added OA to soil significantly increased the biomass and chlorophyll content of D. stramonium. The addition of 10 mmol/kg of OA to soil increased the plant biomass by 67.16 % and chlorophyll b content by 40.01 %. In addition, OA soil treatment significantly enhanced the activities of superoxide dismutase (SOD) by 6.36 %, peroxidase (POD) by 163.13 %, catalase (CAT) by 36.92 %, and ascorbate peroxidase (APX) by 32.12 %, which effectively alleviated the oxidative stress induced by Cr(VI). In contrast, soil treatment with a high concentration of EDTA (10 mmol/kg) significantly reduced plant biomass and chlorophyll content, although it increased the biological concentration factor (BCF) of the stem and leaf, as well as the translocation factor (TF). In conclusion, appropriate amounts of EDTA and OA added to soil can enhance the phytoremediation efficiency of D. stramonium grown in Cr(VI) contaminated soil, with OA added to soil being more effective than addition of EDTA. This study revealed the potential mechanisms of chelating agents EDTA and OA in enhancing the phytoremediation of Cr(VI) contaminated soil by D. stramonium, providing a scientific basis for further optimization of phytoremediation techniques.

Datura stramonium is an invasive herb of the family Solanaceae from Mexico and has been invading seriously in China. The effects of invasive plants on the functional traits of native plants and the stoichiometric characteristics of soil carbon, nitrogen and phosphorus in different habitats were explored by taking the invasive plant D. stramonium and coexisting native plants as the research object. The species, quantity and height of plants in sample plots in farmland, wasteland and roadside habitats were investigated and the specific leaf area (SLA), leaf carbon content (C), nitrogen content (N), carbon-to-nitrogen ratio (C:N), construction cost (CC_mass) and stoichiometric characteristics of soil carbon (C), nitrogen (N) and phosphorus (P) were analyzed. The results showed that compared with the noninvaded area, the species and quantity of native plants decreased in the invaded area, and SLA and leaf N showed a decreasing trend. The plant height of native plants in the invaded area of the farmland and wasteland decreased by 23.19% and 15.26%, respectively, while the height of native plants along the roadside increased by 95.91%. The leaf C:N ratio of native plants in the invaded area along the roadside significantly increased by 54.07%. The plant height and leaf N of D. stramonium in the three habitats were higher than those of the native plants. The soil N in the invaded area of the three habitats increased, with the soil N in the farmland increasing by 21.05%, in the wasteland increasing by 9.82% and along the roadside significantly increasing by 46.85%. The soil carbon-to-phosphorus ratio (C:P) in the three habitats showed an increasing trend. The soil C:P ratio in the farmland increased by 62.45%, in the wasteland it increased by 11.91% and along the roadside it significantly increased by 71.14%. These results showed that invasion by D. stramonium has a great effect on the local ecosystem, and it has a high ability to capture resources. D. stramonium can improve its own competitiveness by enhancing invasiveness by changing the functional traits of native plants and the stoichiometric characteristics of soil C, N and P, which may be the reason for its invasive success.