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Background and aims <p>Chromium (Cr) contamination poses a significant threat to rice safety, yet the mechanisms governing Cr(III) bioavailability under flooded paddy conditions remain poorly understood, particularly the role of chemical speciation.</p> Methods <p>This study investigated the contrasting uptake, translocation, and subcellular distribution of organic-complexed Cr (EDTA-Cr) and inorganic Cr (CrCl<sub>3</sub>) in hydroponically grown rice.</p> Results <p>Inorganic CrCl<sub>3</sub> rapidly hydrolyzed into colloidal particles (350.2&#xa0;nm diameter, 61.1% of total Cr), enhancing root surface adsorption, while EDTA-Cr remained stable in solution due to its high chelation strength. Rice accumulated 7.2-fold more CrCl<sub>3</sub> in roots and 4.0-fold more in shoots compared to EDTA-Cr, with translocation factors (shoot/root ratio) of 0.61 for CrCl<sub>3</sub> versus 0.15 for EDTA-Cr. Subcellular analysis showed 88.0% of CrCl<sub>3</sub> sequestered in root cell walls, whereas 70.0% of EDTA-Cr penetrated organelles and cytosol, triggering early toxicity and limiting translocation.</p> Conclusions <p>The study elucidates a speciation-dependent bioavailability mechanism: CrCl<sub>3</sub> colloids act as reservoirs, gradually releasing bioavailable Cr<sup>3+</sup> via root exudate-mediated dissolution, while EDTA-Cr bypasses adsorption and directly enters cells, accelerating toxicity thresholds.</p>

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EDTA-chelated and inorganic Cr(III) in rice: speciation-dependent bio availability controls root uptake dynamics

  • 期刊论文

  • 发表日期：

    2026年2月9日

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  • Jingjing Li,
  • Kai Xu,
  • Weichao Guo,
  • Ting Liu,
  • Shengsheng Sun,
  • Tenghaobo Deng,
  • Chao Jin,
  • Yetao Tang,
  • Rongliang Qiu

摘要

Background and aims

Chromium (Cr) contamination poses a significant threat to rice safety, yet the mechanisms governing Cr(III) bioavailability under flooded paddy conditions remain poorly understood, particularly the role of chemical speciation.

Methods

This study investigated the contrasting uptake, translocation, and subcellular distribution of organic-complexed Cr (EDTA-Cr) and inorganic Cr (CrCl3) in hydroponically grown rice.

Results

Inorganic CrCl3 rapidly hydrolyzed into colloidal particles (350.2 nm diameter, 61.1% of total Cr), enhancing root surface adsorption, while EDTA-Cr remained stable in solution due to its high chelation strength. Rice accumulated 7.2-fold more CrCl3 in roots and 4.0-fold more in shoots compared to EDTA-Cr, with translocation factors (shoot/root ratio) of 0.61 for CrCl3 versus 0.15 for EDTA-Cr. Subcellular analysis showed 88.0% of CrCl3 sequestered in root cell walls, whereas 70.0% of EDTA-Cr penetrated organelles and cytosol, triggering early toxicity and limiting translocation.

Conclusions

The study elucidates a speciation-dependent bioavailability mechanism: CrCl3 colloids act as reservoirs, gradually releasing bioavailable Cr3+ via root exudate-mediated dissolution, while EDTA-Cr bypasses adsorption and directly enters cells, accelerating toxicity thresholds.