Spatiotemporal dynamics of root exudates drive microbial adaptation mechanisms under day-night alterations in constructed wetlands

Root exudates, as plant-derived metabolites, play a pivotal role in shaping the assembly of rhizosphere microorganisms by acting as nutrients and signals. However, the spatial–temporal dynamics of root exudates remained unknown and thus also, if the dynamic changes in root exudates mediated the assembly of rhizosphere microorganisms. In this study, we conducted an in-depth assessment of root exudates, examining the composition and functional attributes of rhizosphere microorganisms, alongside the pollutant removal performance of constructed wetlands (CWs) under spatial–temporal conditions. Results suggested that nutrient-rich root exudates potentially facilitate the emergence of intricate and resilient microbial communities harboring a plethora of functional microorganisms under light conditions. The function prediction results indicated that the relative abundances of genes related to C and N transformation were enhanced under light conditions. Accordingly, increased microbial metabolic activity would enhance the pollutant removal performance in CWs. Remarkably, the removal efficiencies of COD (82.79 %), NH₄⁺-N (76.72 %), TN (28.29 %), and NO₃^–-N (94.73 %) were enhanced under light conditions. Furthermore, a higher content of root exudates was discerned at the upper layer, leading to an enhancement in the carbon and nitrogen metabolisms of CWs. These findings emphasized root exudate-induced divergence in microbiota dynamics and pollutant removal in CWs, providing valuable mechanistic insights for the adaption of microbiota in response to spatial–temporal variation.