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Endpoint-specific dose-response of nitrogen-doped carbon quantum dots in tomato seed germination and root elongation
Qi Wang1, Hao-Ran Song1, Wen-Hao Su1
1Department of Agricultural Engineering, College of Engineering, China Agricultural University, Beijing, China.
Background:
It is important to understand how nano-enabled materials influence plants in order to interpret concentration-dependent responses and assess agricultural potential. This study evaluated nitrogen-doped carbon quantum dots (N-CQDs) in two independent tomato (Solanum lycopersicum L.) assays involving seed germination and seedling root exposure.
Results:
The synthesized N-CQDs were approximately 3 nm in diameter, water-dispersible, and photoluminescent. Tomato seeds and 3-week-old seedlings were exposed to 0-400 mg L-1 N-CQDs by seed soaking and root immersion for 48 h, respectively. Germination showed a peaked response, increasing from 56.67% in the control to 82.50% at 50 mg L-1, followed by weaker stimulation at higher concentrations. In the seedling assay, plant height and fresh weight increased significantly at all tested concentrations, with no decline up to 400 mg L-1. A constrained Hill1 model provided a descriptive fit to the mean relative growth index trajectory (R2 = 0.9994) and yielded an estimated half-maximal effective concentration (EC50) of 67.91 mg L-1, indicating an apparent tendency toward stabilization at higher concentrations. Whole-plant fluorescence imaging revealed concentration-associated signals that were more evident in visible root and basal-stem regions immediately after treatment and gradually decreased over 25 days. These signals were interpreted as treatment-associated optical dynamics rather than direct evidence of nanoparticle uptake, translocation, or accumulation.
Conclusion:
Tomato responses to N-CQDs differed between the two assays, showing that concentration-response patterns depended on exposure and growth context. The findings provide a quantitative basis for further evaluation of N-CQDs in plants, although denser concentration gradients, direct exposure quantification, physiological measurements, and longer term safety assessments remain necessary. © 2026 Society of Chemical Industry.
