Effects of carbon dots on Cucumis melo L. development: An NMR-based metabolomics and metabolic pathways analysis approach

The use of carbon quantum dots (CQDs) as biostimulants presents a promising tool for sustainable agriculture by enhancing plant metabolism and crop quality. Although, the precise metabolic mechanisms remain poorly understood. In this study, we investigated the effects of CQD-based formulation on the growth and metabolic profile of Cucumis melo L. BRS Araguaia using NMR metabolomics along with metabolic pathway analysis. Agronomic and physicochemical parameters of the leaf and fruit samples under foliar application were assessed (fruit weight, total and internal diameter, pulp thickness, firmness, and °Brix) at concentrations (0, 12, 24, 36, and 48 g/L) and three developmental stages. The resulting spectral data analyzed using multivariate statistical models reveals that foliar application significantly reduced methanol and sucrose/glucose while increasing citric acid across development stages. Analysis of the fruit pulp revealed a critical metabolic shift: treated plants exhibited an accumulation of simple sugars (glucose and fructose) and a decrease in sucrose, correlated with an increase in fruit °Brix. These findings suggest that the CQDs enhance nutrient uptake and regulate growth at the molecular level. Additionally, NMR analysis of treated leaves and pulp revealed modifications in metabolic pathways, including carbohydrate metabolism, amino acid biosynthesis, and cell growth. We conclude that foliar application of CQD at 24 g/L is an effective strategy to improve melon fruit quality by enhancing sweetness. These findings could enhance agricultural practices, promote sustainability, and drive biotechnological innovation by optimizing resource use and strengthening plant resilience.