Geometry-Dependent Effects of Ultrasmall Carbon-Based Nanomaterials on Maize Germination via Distinct Transport and Oxidative Responses.

The agricultural application of ultrasmall carbon-based nanomaterials (UCBMs) is hindered by inconsistent bioeffects, with their intrinsic geometry underexplored. To elucidate structure-activity relationships, we synthesized a library of UCBMs including two spherical carbon dots (CDs) from glucose (CDs-Glu) and citric acid (CDs-CA) and three size-variant sheet-like graphene quantum dots (GQDs) and then evaluated their impacts on maize ( L. cv. B73) germination and seedling growth. Morphology dictated differential responses: CDs promoted germination and systemic growth via efficient translocation, aquaporin (AQP) upregulation for enhanced water uptake, and reactive oxygen species (ROS) quenching. Conversely, GQDs accumulated in radicles, inducing size-dependent oxidative stress and AQP suppression, thereby inhibiting radicle elongation. Remarkably, this localized stress elicited a systemic defense, boosting plumule growth despite minimal GQD translocation. These findings establish geometry-dependent rules for UCBM-plant interactions, guiding the design of safe, effective agro-nanomaterials.