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Main conclusion <p><b>Hierarchical ROS network regulating rice root iron plaque formation, Fe speciation, mineral crystallinity, and absorption of nutrient elements has been revealed.</b></p> Abstract <p>The root iron plaque (RIP) of rice plays a critical role in heavy metal adsorption and rhizosphere environment regulation. However, the regulatory mechanisms of reactive oxygen species (ROS) in RIP formation remain poorly understood. This study investigated hydroponically cultivated rice under Fe(II) concentration gradients (50–200&#xa0;mg L<sup>−1</sup>) and water management regimes [contrast of continuous waterlogging (CW) with alternate wetting and drying (AWD)]. Using ROS scavengers [Cu(II), DMTU, TBA] to specifically inhibit O<sub>2</sub>·<sup>−</sup>, H<sub>2</sub>O<sub>2</sub>, and ·OH generation, we systematically elucidated ROS-mediated regulation of RIP formation, Fe redox speciation, and mineralogical structure. Key findings include: (i) ROS scavenging experiments revealed O<sub>2</sub>·<sup>−</sup> as the dominant contributor to RIP formation (17.55 ± 0.89% reduction after scavenging), followed by H<sub>2</sub>O<sub>2</sub> (11.86 ± 0.45%) and ·OH (6.35 ± 0.34%); (ii) O<sub>2</sub>·<sup>−</sup> depletion reduced Fe(III)/Fe(II) ratios from 4:1 to 1:1, suppressed crystalline mineral formation (e.g., hematite), and increased weakly crystalline siderite proportions; (iii) XPS and XRD analyses demonstrated that ROS drive Fe(II) oxidation and mineral phase transitions by oxidative chain reactions (O<sub>2</sub>·<sup>−</sup> → H<sub>2</sub>O<sub>2</sub> → ·OH), with O<sub>2</sub>·<sup>−</sup> being pivotal for maintaining high oxidation states and crystallinity in RIP. (iv) The mineral crystallinity of RIP affects its regulatory effect on nutrient elements. Scavenging O<sub>2</sub>·<sup>−</sup> treatment results in low crystallinity of RIP, which weakens its adsorption and fixation capacity for trace elements, such as Mn, Zn, and Cu. Consequently, the contents of Mn, Zn, and Cu in the iron plaque are low, while their contents in rice plants are high. This study unveils a hierarchical ROS regulatory network governing RIP formation, providing theoretical foundations for optimizing RIP functionality through water management strategies.</p>

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The impact of reactive oxygen species on Fe valence speciation, mineral crystallinity, and nutrient element uptake in rice root iron plaque

  • 期刊论文

  • 发表日期：

    2026年1月16日

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  • Xiaoyu Wang,
  • Junru Huang,
  • Qing Zhang,
  • Yuxi Feng,
  • Yujuan Lin,
  • Meina Liang

摘要

Main conclusion

Hierarchical ROS network regulating rice root iron plaque formation, Fe speciation, mineral crystallinity, and absorption of nutrient elements has been revealed.

Abstract

The root iron plaque (RIP) of rice plays a critical role in heavy metal adsorption and rhizosphere environment regulation. However, the regulatory mechanisms of reactive oxygen species (ROS) in RIP formation remain poorly understood. This study investigated hydroponically cultivated rice under Fe(II) concentration gradients (50–200 mg L−1) and water management regimes [contrast of continuous waterlogging (CW) with alternate wetting and drying (AWD)]. Using ROS scavengers [Cu(II), DMTU, TBA] to specifically inhibit O2·−, H2O2, and ·OH generation, we systematically elucidated ROS-mediated regulation of RIP formation, Fe redox speciation, and mineralogical structure. Key findings include: (i) ROS scavenging experiments revealed O2·− as the dominant contributor to RIP formation (17.55 ± 0.89% reduction after scavenging), followed by H2O2 (11.86 ± 0.45%) and ·OH (6.35 ± 0.34%); (ii) O2·− depletion reduced Fe(III)/Fe(II) ratios from 4:1 to 1:1, suppressed crystalline mineral formation (e.g., hematite), and increased weakly crystalline siderite proportions; (iii) XPS and XRD analyses demonstrated that ROS drive Fe(II) oxidation and mineral phase transitions by oxidative chain reactions (O2·− → H2O2 → ·OH), with O2·− being pivotal for maintaining high oxidation states and crystallinity in RIP. (iv) The mineral crystallinity of RIP affects its regulatory effect on nutrient elements. Scavenging O2·− treatment results in low crystallinity of RIP, which weakens its adsorption and fixation capacity for trace elements, such as Mn, Zn, and Cu. Consequently, the contents of Mn, Zn, and Cu in the iron plaque are low, while their contents in rice plants are high. This study unveils a hierarchical ROS regulatory network governing RIP formation, providing theoretical foundations for optimizing RIP functionality through water management strategies.