Visualization and Quantification of the Impact of Humic Acid on Zinc Accumulation in Aquatic Plants Using a Low-Molecular-Weight Fluorescent Probe

Abstract

The main aims of this study were to investigate the impact of humic acid (HA) on zinc (Zn) accumulation in aquatic plants and to study a low-molecular-weight Zn2+-selective fluorescent probe to visualize and quantify the tissue-level Zn concentrations. Ceratophyllum demersum and Aldrovanda vesiculosa were exposed to solutions containing Zn (1 and 3 mg/L), HA (0.5 mg/L), and Zn with HA for nine days. The Zn accumulation (mg/g) in the plants was measured by ICP-OES and we applied a Zn2+-selective fluorescent probe with a low molecular weight to the analysis of Zn in C. demersum plant cells using fluorescence microscopy and ImageJ software. The application of HA reduced the Zn accumulation significantly (p 0.05) in both plants. Results obtained from ImageJ revealed a strong positive correlation between fluorescence intensity and the Zn accumulation in C. demersum (r = 0.988). We showed that the application of HA reduced the Zn accumulation in both plants, and successfully visualized and quantified that a Zn2+-selective fluorescent probe with a low molecular weight can be applied to the diagnosis of Zn osmosis into a cell or tissue on the basis of fluorescence intensity.

Keywords

• aquatic plants
• humic acid
• humic acid-metal complexes
• zinc
• zn2+ fluorescent probe