Microscale Spatiotemporal Variation and Generation Mechanisms of Reactive Oxygen Species in the Rhizosphere of Ryegrass: Coupled Biotic–Abiotic Processes

Abstract

Reactive oxygen species (ROS) play key roles in soil biogeochemical processes, yet the occurrence and accumulation of ROS in the rhizosphere are poorly documented. Herein, we first developed a ROS-trapping membrane to in situ determine ROS in the ryegrass rhizosphere and then quantified the temporal and spatial variations of representative ROS (i.e., O 2•� , H 2 O 2 , and • OH). Fluorescence imaging clearly visualized the production of ROS in the rhizosphere. Both O 2•� and H 2 O 2 content increased first and then declined throughout the life cycle of ryegrass, while • OH concentration decreased continuously. Spatially, ROS contents remained at a relatively high level at 0−5 mm and then descended with increasing distance. The concentrations of ROS in different soils followed the order of black soil > latosol soil > yellow-brown soil > tier soil ∼ red soil. Analysis of soil properties suggested that both biotic factors (microbial community) and abiotic factors (Fe(II) and water-soluble phenols) played critical roles in ROS production. The combined processes, including Fe(II) and water-soluble phenol-mediated electron transfer, microbial community-driven extracellular O 2 •� release, and Fe(II)/Fe(III) cycling, may be responsible for ROS production. These findings provide insights into ROS-associated rhizosphere effects and inspiration for the phytoremediation of pollutants and element cycling.

Stability and Biotransformation of 6:2 Fluorotelomer Sulfonic Acid, Sulfonamide Amine Oxide, and Sulfonamide Alkylbetaine in Aerobic Sludge

“…In contrast, perfluorooctane amide amine oxide (PFOANO) and PFOSNO, both containing terminal amine oxide moieties, underwent more pronounced and extensive abiotic transformation in sterilized soil, resulting in the terminal products of perfluorooctane amide propionic acid and FOSA, respectively . The differences in abiotic degradation behavior between ECF-based amine oxides in soil and 6:2 FTNO in sludge can be attributed to the abundant natural organic matter and iron minerals present in the soil, which are known to facilitate the production of ROS, thereby promoting the chemical degradation of FOSA-based amine oxides. − …”

Fe-Based Nanomaterials and Plant Growth Promoting Rhizobacteria Synergistically Degrade Polychlorinated Biphenyls by Producing Extracellular Reactive Oxygen Species

“…We have previously found that Fe-based nanomaterials assisted plant rhizoremediation of PCB-contaminated soil . Meanwhile, it was recently demonstrated that the plant rhizosphere is a ubiquitous but generally unrecognized hotspot for ROS production. , It is well-known that the occurrence of biogenic free radicals is a widespread biogeochemical process that can modulate the fate of pollutants. This study not only demonstrates the ability of PGPR extracellular ROS to degrade organic pollutants but also illustrates the significant contribution of nZVI to accelerate this process.…”

New Barrier Role of Iron Plaque: Producing Interfacial Hydroxyl Radicals to Degrade Rhizosphere Pollutants

“…Therefore, we hypothesize that iron plaque can reduce oxygen secreted by the roots to produce ·OH. Though the production of ·OH in rhizosphere has been reported, , the role of iron plaque in ·OH production and the characteristics of ·OH produced by iron plaque remain unknown. Since the iron plaque is a significant heterogeneous interface between the root and soil, the production of ·OH by iron plaque may be distinct from the production of ·OH by the bulk phase of rhizosphere.…”