The physiological mechanism of the tolerance of Eichhornia crassipes (Mart.) Solms to cadmium

Abstract

The tolerance of plants to Cd is a scientific and interesting issue for phytoremediation. In the current study, we attempt to reveal the physiological mechanism of the tolerance of Eichhornia crassipes to cadmium (Cd) by using hydroponic experiments. The results showed that the Cd absorption of E. crassipes was dose-dependent and the absorbed Cd was mainly maintained in the root. The fresh weight was greatly affected by Cd in the early stage of aquatic cultivation. The negative effect of Cd on E. crassipes is dose-dependent, but E. crassipes might adapt to moderate Cd pollution over time. The Cd stimulated the opening of the stomata, and the cell tightness ratio of E. crassipes increased with rising Cd concentrations. The administration of moderate levels of Cd stimulated the release of soluble protein, free proline, malondialdehyde, and soluble polysaccharide. Cd administration also stimulated the activity of superoxide dismutase, peroxidase (POD), catalase, and ascorbic acid peroxidase of E. crassipes, except for POD activity at the highest Cd concentration. This indicates that the physiological mechanism of the tolerance of E. crassipes to Cd depends on osmotic regulation, reduction of lipid peroxidation, improvement of antioxidant properties, increasing palisade tissue while decreasing sponge tissue, and increasing stomatal conductance.

Graphical Abstract

Highlights

1. The physiological mechanism of the tolerance of Eichhornia crassipes to Cd depends on osmotic regulation, reduction of lipid peroxidation, improvement of antioxidant properties, and increasing palisade tissue and stomatal conductance.

2. The absorption of Cd is mainly retained in the root of E. crassipes.

3. The use of E. crassipes for Cd phytoremediation in highly polluted aquatic environments will be limited due to the reduction of tolerance and the significant decrease of biomass. It will be effective in remediating sites with moderate pollution (≤2 mg/L).

Keywords:

• Antioxidant properties
• aquatic environment
• cell tightness ratio
• lipid peroxidation
• osmotic regulation
• palisade tissue
• stomata

Acknowledgments

We thank two anonymous reviewers for their constructive comments that improved this manuscript.

Disclosure statement

We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us. We state that there is no conflict of interest in this manuscript.

Additional information

Funding

This study was partly supported by the Central Government Guides Local Science and Technology Development Projects (2019L3013).