Mechanism for Fe(III) to decrease cadmium uptake of wheat plant: Rhizosphere passivation, competitive absorption and...

Area of Science:

• Environmental Science
• Plant Physiology
• Soil Science
• Biogeochemistry

Background:

• Cadmium (Cd) contamination in soils poses risks to wheat production and food safety.
• Dissolved iron(III) (Fe(III)) and Fe(III)-containing minerals are known to reduce Cd accumulation in plants, but the underlying mechanisms require elucidation.

Purpose of the Study:

• To investigate the mechanism by which dissolved Fe(III) mitigates Cd uptake in wheat plants.
• To analyze the influence of varying Fe(III) concentrations and Cd(II) levels on Cd uptake dynamics.

Main Methods:

• Hydroponic experiments were conducted to assess Cd uptake in wheat under different Fe(III) (0–2000 μmol L⁻¹) and Cd(II) (0–20 μmol L⁻¹) concentrations.
• Analysis included rhizosphere passivation, competitive absorption, physiological regulation, gene expression profiling (TaNramp5, TaHMA, TaPDR8), and measurement of CaCl₂-extractable Cd.

Main Results:

• Dissolved Fe(III) significantly reduced Cd uptake via rhizosphere passivation (Fe(III) oxides adsorbed >80.4% Cd(II)) and competitive absorption, decreasing CaCl₂-extractable Cd by 52.7% at 2000 μmol L⁻¹ Fe(III).
• Fe(III) potentially reduced Cd(II)-organic acid complex formation and modulated gene expression, down-regulating Cd uptake/transport genes (TaNramp5, TaHMA) and up-regulating a Cd efflux gene (TaPDR8-4A7A).
• The inhibitory effect of Fe(III) on Cd uptake diminished with increasing Cd(II) concentrations.

Conclusions:

• Dissolved Fe(III) effectively reduces Cd accumulation in wheat through multiple mechanisms including rhizoplane immobilization, competitive inhibition, and altered gene expression.
• This study provides a scientific basis for using dissolved Fe(III) and Fe(III)-minerals to remediate Cd-contaminated soils and ensure safe wheat production.