Roots or exudates? Rhizosphere enzyme hotspots reveal contrasting nitrogen‐acquisition strategies in maize under nitrogen limitation

Abstract Plants acclimate to nitrogen limitation by expanding root biomass or recruiting microbes via exudates, yet the integrative role of these strategies in spatially organizing rhizosphere enzymatic hotspots remains largely unexplored. Here, we combined soil zymography with microbiome–metabolome analysis to investigate the mechanisms underlying rhizosphere enzymatic hotspot formation in two maize hybrids with contrasting below‐ground responses to nitrogen limitation. Results showed that ZD958 adopted a root biomass‐centric strategy, increasing rhizosphere N‐acetyl‐β‐glucosaminidase activity by 36% and overall rhizosphere extent by 103% through root proliferation and microbial synergy. In contrast, XY335 invested carbon in root exudates, restructuring its rhizosphere microbiota and upregulating genes encoding β‐glucosidase and N‐acetyl‐β‐glucosaminidase, which resulted in a 19% increase in β‐glucosidase activity and a 77% expansion of its rhizosphere extent under low‐N conditions. Network analyses identified Acidobacteriota as keystone taxa, accounting for ~95% of core microbial interactions and showing strong co‐occurrence with root‐derived metabolites. Consistently, Acidobacteriota carrying β‐glucosidase‐ and N‐acetyl‐β‐glucosaminidase‐encoding genes increased by 34%–71% under N deficiency. Partial least squares path modelling revealed that root exudates had a stronger influence on rhizosphere microbial structure and enzymatic hotspot formation than soil N levels or root biomass. Synthesis. These findings reveal two complementary N‐acquisition strategies in maize: exudate‐mediated microbial recruitment versus root biomass‐driven enzymatic expansion. Unravelling these trade‐offs offers essential insights into plant–microbe coordination for improving nutrient acquisition in low‐N soils.