Carbon dots promote plant growth via coordinated regulation of nutrient uptake and photosynthesis: Evidence from...

Carbon-based nanomaterials have shown great potential to enhance plant productivity. However, how they affect the linkage among nutrient uptake, photosynthesis, and biomass accumulation remains unclear. Here, we systematically investigated the dose-dependent effects of carbon dots (CDs) on nutrient uptake, photosynthesis, and growth of pakchoi (Brassica campestris L.) at experimental concentrations ranging from 0 to 80 mg/L. A multivariate modeling framework combining partial least squares structural equation modeling (PLS-SEM), principal component analysis (PCA), and physiological assays was applied to capture the complex causal relationships among these variables. PLS-SEM revealed that CDs-induced nutrient enhancement significantly promoted photosynthesis, which in turn served as a key mediator of plant growth. Elemental analysis and XPS characterization showed that CDs bind ions and potentially induce Ca²⁺ signaling, facilitating uptake and translocation of essential nutrients (Fe, Ca, Mg, and K). Concurrently, CDs enhanced photosynthetic efficiency by improving stomatal conductance, chlorophyll content, and PSII electron transport. Notably, these enhancements exhibited a non-monotonic dose-response manner, with intermediate treatments causing transient metabolic disruption. At higher doses, activation of antioxidant enzymes (SOD, CAT, APX, and POD) mitigated oxidative damage and maintained redox homeostasis. Together, our findings reveal a coordinated physiological response to amendment of CDs, with a conceptual model linking nutrient assimilation, photosynthesis, and redox regulation to plant growth. This work offers mechanistic insights into plant-nanomaterial interactions and supports the rational design of nanobiostimulants for sustainable agriculture.