Biomass-derived carbon dots (CDs) are promising nanotools for agricultural applications and function as a reactive oxygen species (ROS) scavenger to alleviate plant oxidative stress under adverse environments. Nevertheless, plants need ROS burst to fully activate Ca 2+ -regulated defensive signaling pathway. The underlying mechanism of CDs to improve plant environmental adaptability without ROS is largely unknown. Here, Salvia miltiorrhiza-derived CDs triggered ROS-independent Ca 2+ mobilization in plant roots. Mechanistic investigation attributed this function mainly to the hydroxyl and carboxyl groups on CDs. CDs-triggered Ca 2+ mobilization was found to be dependent on the production of cyclic nucleotides and cyclic nucleotide-gated ion channels. Lectin receptor kinases were verified as essential for this Ca 2+ mobilization. CDs hydroponic application promoted Ca 2+ signaling and plant environmental adaptability under salinity and nutrient-deficient conditions. All these findings uncover that CDs have a Ca 2+ -mobilizing property and thus can be used as a simultaneous Ca 2+ signaling amplifier and ROS scavenger for crop improvement.

In China, iron (Fe) availability is low in most soils but cadmium (Cd) generally exceeds regulatory soil pollution limits. Thus, biofortification of Fe along with mitigation of Cd in edible plant parts is important for human nutrition and health. Carbon dots (CDs) are considered as potential nanomaterials for agricultural applications. Here, Salvia miltiorrhiza‐derived CDs are an efficient modulator of Fe, manganese (Mn), zinc (Zn), and Cd accumulation in plants. CDs irrigation (1 mg mL−1, performed every week starting at the jointing stage for 12 weeks) increased Fe content by 18% but mitigated Cd accumulation by 20% in wheat grains. This finding was associated with the Fe3+‐mobilizing properties of CDs from the soil and root cell wall, as well as endocytosis‐dependent internalization in roots. The resulting excess Fe signaling mitigated Cd uptake via inhibiting TaNRAMP5 expression. Foliar spraying of CDs enhanced Fe (44%), Mn (30%), and Zn (19%) content with an unchanged Cd accumulation in wheat grains. This result is attributed to CDs‐enhanced light signaling, which triggered shoot‐to‐root Fe deficiency response. This study not only reveals the molecular mechanism underlying CDs modulation of Fe signaling in plants but also provides useful strategies for concurrent Fe biofortification and Cd mitigation in plant‐based foods.