Nanoenabled biostimulants as rhizosphere engineers: how surfaces and carriers rewire root exudation and microbial guilds

Nanoenabled biostimulants with explicitly designed surface chemistry, carrier architecture, and release kinetics can systematically reprogram root exudation profiles, selecting and stabilizing beneficial rhizosphere guilds in ways that conventional formulations cannot; claims that can be tested with coordinated exudate metabolomics, trait-based microbiome profiling, and field-scale performance trials. The review starts with the practical constraint that most currently developed nanoenabled biostimulants are described in terms of materials and doses, whereas their actual leverage lies in how they influence root exudation patterns and the assembly of trait-based rhizosphere guilds. It then proceeds from along the proposed mechanistic sequence from nanocarrier surfaces and release kinetics, through plant physiological and exudate responses, as well as through guild-level microbiome restructuring under realistic soil-climate-management filters, from beneficial rewiring to off-target or ecotoxic outcomes. Building on this mechanistic spine, the paper goes on to integrate multi-omics, trait-based ecology, and nanoparticle fate modeling to define experimental and computational frameworks that can predict nano-exudate-guild linkages rather than describe them post hoc. The contents of this review are summarized by merging these insights into explicit design principles, safe operating spaces, and testable hypotheses that can be used to transition the next generation of nanoenabled biostimulants away from exploratory approaches and towards the use of predictive, microbiome-compatible products.