Physiological response of Bidens pilosa to cadmium stress monitored by fourier transform infrared spectroscopy

Abstract

The cadmium (Cd) pollution of soil causes serious environmental problems. The present paper deals with the physiological response of the changes in chemical components in the root, stem and leaf of Bidens pilosa seedlings stressed by excess cadmium ions (Cd²⁺) using Fourier transform infrared spectroscopy technique (FTIR). Cadmium accumulation in plant and distribution in subcellular by atomic absorption spectroscopy were tested under different concentrations cadmium stress. Results indicated that at a Cd concentration of 7 mg·L^–1, B. pilosa maintained normal growth without visible Cd toxicity symptoms, though biomass was reduced compared to controls. FTIR analysis revealed that the overall peak shapes of roots, stems, and leaves remained largely unchanged before and after heavy metal treatment, suggesting that the structural integrity of plant organs was not compromised. However, shifts in specific functional group absorption peaks, including hydroxy (3387–3417 cm^–1), carboxyl (1411–1419 cm^–1), and amide groups (1635 cm^–1), were observed, indicating their involvement in the heavy metal absorption process. The characteristic peak intensity of leaves was higher at high Cd concentration than at medium-low Cd concentration, while peaks in stems and roots remained consistent with or exceeded those of the control group. Cd predominantly accumulated in cell walls (46.21%–55.32%) and was minimally distributed in chloroplasts and mitochondria (4.11%–8.43%). These findings suggest that B. pilosa exhibits strong tolerance to Cd-contaminated soil and has significant potential for phytoremediation. The FTIR method offers strong evidence supporting the development of phytoremediation technology.