Enhancing the Growth and the Quality of Astragalus membranaceus by Leveraging Proanthocyanidin-Derived Highly Water-Soluble Carbon Dots

Medicinal plants are of great importance in healthcare, possessing significant economic importance worldwide. However, excessive chemical application and biotic and abiotic stresses increase concerns about their growth and quality. Here, we investigated the enhancement of the growth and quality of Astragalus membranaceus by highly water-soluble carbon dots derived from proanthocyanidins. Based on the findings, the carbon dots exhibited uniform morphologies with a size of 2.86 nm and were rich in functional groups. Moreover, such highly water-soluble carbon dots could be taken up by the roots and transported to the entire plant, resulting in a 36.41% enhancement of the overall photosynthesis rate. More importantly, the content of bioactive compounds significantly increased in the plants. Astragaloside IV, astragaloside I, and calycosin-7-O-β-d-glucoside were increased by 46.33, 56.72, and 31.5%, respectively. Transcriptome analysis confirmed that the carbon dots treatment enhanced the secondary metabolite content and upregulated related gene expression, increasing flavonoid and triterpenoid contents. Our results suggest that proanthocyanidin-derived highly water-soluble carbon dots possess significant potential in medicinal plant cultivation, presenting a novel opportunity to exploit such renewable materials.