The Foliar Application of Carbon Dots Promoted the Photosynthesis Performance, Growth, and Pharmaceutical Ingredient Enrichment in <i>Isatis tinctoria</i> L

<i>Isatis tinctoria</i> L., an important abundant medicinal plant, faces significant challenges related to reduced yield and medicinal efficacy. Herein, carbon dots (CDs) are utilized to enhance the growth and enrichment of pharmaceutical ingredients in <i>I. tinctoria</i> L. Owing to their high photoinduced electron conversion and efficient electron transfer properties, CDs significantly improve the rate of photosynthesis in <i>I. tinctoria</i> L., leading to 128 and 27% increase in the biosynthesis of active components indigo and indirubin, respectively. Transcriptome sequencing reveals that CDs promote the upregulation of genes involved in indole synthesis, including <i>ASA1</i> and <i>TSA1</i>. Additionally, we derive an experimentally inferred estimate of the effect of genes <i>CYP81F3</i> and <i>CYP74B2</i> in the hydroxylation of indole to form indoxyl (i.e., 2-hydroxyindole). This study underscores the potential of CDs as a transformative agent in the cultivation and enhancement of medicinal plants, specifically <i>I. tinctoria</i> L. The observed upregulation of key biosynthetic genes and the resultant increase in active component yields highlight the promise of CDs in agricultural biotechnology. Moreover, the positive impact on photosynthesis efficiency not only augments the quality of medicinal compounds but also suggests broader applications in other economically important crops.