Rhizosphere Reactive Oxygen Species: Detection Methods, Distribution Characteristics, Production Mechanisms, and Environmental Effects

The rhizosphere, the zone around the roots of plants, including the root, the soil on the root itself, and the surrounding area soil, is the hotspot for the production of reactive oxygen species (ROS). Functioning as redox signaling mediators, rhizosphere ROS regulate a series of key processes in the rhizosphere microenvironment. These biological and geochemical events cover root morphogenesis, the formation of beneficial plant-microbe symbioses, and element biogeochemical transformations. Nevertheless, the pronounced spatial heterogeneity, drastic redox fluctuations, and intricate interfacial interactions within the rhizosphere impede accurate in situ detection of ROS. Beyond technical barriers, the coupled regulatory effects exerted by biotic and abiotic factors on ROS dynamics, together with the associated ecological outcomes induced by rhizosphere ROS, remain difficult to fully disentangle. This review first discusses updated strategies and optimized methodologies for in situ rhizosphere ROS monitoring. We then characterize the spatial distribution patterns and microscale hotspots of rhizosphere ROS. Importantly, this review dissects the complex coupled regulatory network formed by biotic, abiotic, and environmental factors and molecular regulatory pathways that control ROS production. Furthermore, this study systematically illustrates diverse environmental effects triggered by rhizosphere ROS. Finally, the present work identifies prevailing research gaps and unresolved limitations in current studies. On this basis, we further propose targeted research directions for future studies in this field, providing comprehensive theoretical evidence to deepen the understanding of rhizosphere ROS formation and their mediated biogeochemical processes.