Tolerance mechanism and phytoremediation potential of Pistia stratiotes to zinc and cadmium co-contamination

Abstract

Pistia stratiotes can not only effectively remediate eutrophic water, but also displays strong absorption and bioaccumulation abilities for heavy metals. However, it has not been well-understood how the plant resists the combined stress of heavy metals. In these experiments, the morphophysiological traits, the ascorbate-glutathione (AsA-GSH) cycle, the glyoxalase system, and the contents of zinc (Zn) and cadmium (Cd) were investigated under Zn and Cd co-pollution. The AsA-GSH cycle and glyoxalase system could coordinately alleviate the oxidative and carbonyl stress, which was identified as an important tolerance mechanism. With Zn₅₀Cd₁, Zn₅₀Cd₁₀, Zn₁₀₀Cd₁, and Zn₁₀₀Cd₁₀ treatments for 18 days, 90.75–93.69% of Zn and 88.13–96.96% Cd accumulated in the roots. Treatments with Zn₅₀Cd₅₀, and Zn₁₀₀Cd₅₀ for 18 days resulted in a decrease of stress tolerance and chlorophyll content in leaves, an increase in plasma membrane permeability, a massive accumulation of methylglyoxal (MG), and visible toxic symptoms. Additionally, the bioaccumulation factor (BCF) for roots and shoots and the translocation factor (TF) were >1, and the content of Cd in shoots was no <100 mg·kg⁻¹. This indicated P. stratiotes was a Cd hyperaccumulator and have great potential for the phytoremediation of heavy metal contaminated water.

Novelty statement Pistia stratiotes, a cadmium hyperaccumulator, has great application potential for the phytoremediation of zinc and cadmium co-polluted water.

Keywords:

• Pistia stratiotes
• zinc and cadmium co-contamination
• bioaccumulation and translocation
• tolerance mechanism
• phytoremediation

Acknowledgments

We also thank the Advanced Analysis and Testing Center (AATC) of Nanjing Forestry University for their kind support and LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.

Additional information

Funding

The research was supported by the National Natural Science Foundation of China (grant number 30972408) and Postdoctoral Science Foundation of China (grant number 2020M671509).