Green Fluorescent Carbon Dots Facilitate the Growth and Augment the Salt Tolerance of Rapeseed

Carbon dots (CDs) are a novel class of fluorescent nanomaterials with great potential in agriculture, yet their mechanisms for enhancing plant growth and stress tolerance remain insufficiently understood. This study investigated the effects of green fluorescent CDs on rapeseed (Brassica napus L.) under both salt-stressed and non-stressed conditions. Treatment with CDs significantly enhanced plant growth under salt stress, increasing the fresh weight of shoots and roots by 35.80% and 49.13%, respectively. CDs alleviated salt damage by regulating ion transport, reducing Na+ translocation from roots to shoots, and promoting K+ uptake, thereby increasing the K+/Na+ ratio and maintaining ion homeostasis. Transcriptome analysis further indicated that ion transporter genes, such as BnaC09.HKT1 and BnaA04.AKT1, may play pivotal roles in this process. We examined the impact of CDs on the relationships among the soil, endophytic microbiomes, and plant growth under non-stress conditions. Treatment with CDs increased the fresh weight of rapeseed by 22.11%. Amplicon sequencing analysis revealed that CDs significantly altered the diversity of microbial communities associated with multiple rapeseed niches, particularly soil and root endophytes. Moreover, CDs may contribute to promoting plant growth by enriching beneficial microbial taxa, such as Rhizobium, Flavobacterium, and Peziza. These findings elucidated the dual mechanisms by which CDs enhanced plant salt tolerance through ion transport regulation and stimulated growth by modulating the enrichment of beneficial microbes, offering valuable advancements in sustainable agriculture.