SCREENING OF CADMIUM AND COPPER PHYTOREMEDIATION ABILITY OF TAGETES ERECTA, USING BIOCHEMICAL PARAMETERS AND SCANNING ELECTRON MICROSCOPY-ENERGY-DISPERSIVE X-RAY MICROANALYSIS

摘要

Tagetes erecta thrived in phytotoxic levels of cadmium (Cd; 50-300 mg kg(-1)) and copper (Cu; 150-400 mg kg(-1)) for 21 d. It accumulated high metal contents in its above-ground tissues (3675 mg Cd kg(-1) dry wt and 3948 mg Cu kg(-1) dry wt) and showed greater root to shoot translocation and a high extraction coefficient, all of which pointed toward its potential as a hyperaccumulator. Both Cd stress and Cu stress reduced the plant biomass, foliar area, and number. In addition, there were significant declines in pigment contents as well as boosts in lipid peroxidation levels. However, the plant triggered a number of stress-mitigation strategies to abate reactive oxygen species formed as a result of Cd/Cu excess, mostly via significant augmentation of superoxide dismutase, catalase, glutathione peroxidase, and ascorbate peroxidase activities. Though the root and leaf anatomy revealed some signs of toxic symptoms at 50 mg Cd kg(-1) and at 150 mg Cu kg(-1), as evidenced by scanning electron microscopy, the root showed maximum tolerance, with tolerance indexes of 85.4% and 91.7%, respectively. Energy-dispersive X-ray microanalysis showed specific Ca2+ signals in both root and stomata, which could be associated with a specific signaling pathway leading to increased root metal uptake and stomatal closure. (C) 2017 SETAC