Effect of synthetic and organic chelators application in a calcareous copper-spiked soil on copper phytoremediation potential of Calendula officinalis L.

Using of ornamental plants for phytoremediation of heavy metals (HMs) in soil environments have been grown due to its cheapness and ease of use in urban environments. The aim of this study was to assess the potential use of C. officinalis, for soil copper (Cu) phytoremediation in the presence of different type of chelating agents (Ethylene diamine tetra-acetic acid (EDTA), citric acid (CIT), and tartaric acids (TAR)) in different levels of Cu in a calcareous soil. Moreover, to investigate the effects of stress caused by the use of chelating agents on biochemical changes of C. officinalis, the response of some antioxidant (superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and polyphenol oxidase (PPO)) activity of C. officinalis were evaluated. According to the results, C. officinalis showed an increase in shoot and root Cu concentration in the presence of all chelating agents compared to the control. The highest accumulation of Cu in the root/shoot was observed in EDTA-treated plants. However, an increased Cu level in plant parts (due to consuming of EDTA) was corresponded to lower dry weight in shoot and root; higher H2O2 and malondialdehyde (MDA) contents, and antioxidant activity (APX, PPO, CAT, SOD, and POD) in plants compared to the control treatment. On the contrary, the application of CIT and TAR primarily increased shoot and root dry weight and Cu concentration. Altogether, these results could be suggested that plants possess a well-organized resistance mechanism against oxidative stress caused by using of CIT and TAR.