活性酸素種が米根鉄被膜の鉄価種分、鉱物結晶性、栄養素元素の取り込みに及ぼす影響

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