Distinct root exudation patterns in emergent plants yield similar rhizosphere microbial communities

Emergent plants with different root morphologies show considerable variation in their nitrogen removal capabilities via nitrification and denitrification processes; however, the underlying mechanisms are still unknown. This study investigates how root morphology influences root exudates and rhizosphere microbial communities in two emergent plant species: Zizania latifolia (taprooted) and Pontederia cordata (fibrous-rooted). Root exudates were collected and analyzed using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), revealing distinct metabolic profiles between the two species. Z. latifolia primarily secreted benzenoids, while P. cordata exuded higher levels of lipids and lipid-like molecules. Despite these differences, the rhizosphere bacterial and fungal communities of both plants were similar in both structures and potential functions. Interestingly, the differential metabolites identified in Z. latifolia root exudates, especially amino acids (e.g., denticetic acid and itopride), exhibited significant and positive correlations with denitrifying bacterial genera, such as Pseudomonas and Clostridium, suggesting that these metabolites may play a crucial role in the recruitment of specific microbial communities. These findings highlight the complex interactions between root exudates, rhizosphere microbes, and nitrogen cycling in emergent plants, providing insights for optimizing wetland restoration strategies.