Plant-mediated nitrous oxide emissions.

Plants are increasingly recognized as active contributors to nitrous oxide (N2O) fluxes. However, the physiological and biochemical processes underlying these plant-mediated N2O emissions remain poorly defined. This review synthesizes current understanding of direct N2O production pathways within plants, including chloroplast- and mitochondrial-associated processes involving nitrate and nitrite reductases, as well as cytochrome-mediated reactions under specific conditions. Plant-microbe interactions in the rhizosphere and phyllosphere further influence N2O dynamics. Symbiotic nitrogen-fixing bacteria and ammonia-oxidizing organisms modulate nitrogen availability and transformation, altering net fluxes. Evidence is also growing for conduit-mediated N2O transport from roots to aerial tissues, as well as for foliar N2O uptake, suggesting plants may function as both sources and sinks depending on context. Methodological limitations in separating plant- from microbe-derived N2O are critically evaluated, with a focus on challenges in isotopic tracing and sterile growth conditions. Key plant traits and environmental drivers influencing emissions are identified, including leaf area, root length, stomatal density, and hypoxic stress. This review provides an integrated physiological and ecological perspective on plant-associated N2O fluxes and proposes a framework linking plant traits, microbial partnerships, and environmental conditions to N2O outcomes. Clarifying these mechanisms is essential for incorporating plant processes into global N2O budgets and mitigation strategies.