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 micro-organisms 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 micro-organisms. 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.