Biomass-derived carbon dots enhanced maize (Zea mays L.) drought tolerance by regulating phyllosphere microorganisms and ion fluxes

Enhancing crop drought tolerance is beneficial for increasing crop yield and ensuring food security. This study demonstrates that foliar application of biomass-derived carbon dots (Soy-CDs, 10 mg·L⁻¹) can enhance the drought tolerance of maize, leading to an increase in fresh weight of maize shoots and roots (50.5 % and 54.9 %) and dry weight of maize shoots and roots (40.0 % and 37.7 %), respectively. Meanwhile, Soy-CDs altered the abundance of phyllosphere microorganisms (e.g. Proteobacteria, Deinococcus-Thermus, Verrucomicrobia, and Actinobacteria) of maize under drought stress, which enhanced the nitrogen fixation and stress resistance in maize leaves. Besides, Soy-CDs also promote Ca²⁺ influx and Na⁺ efflux in maize mesophyll cells under drought stress, facilitating the regulation of ion osmotic balance and contributing to the improvement of maize drought tolerance. Furthermore, Soy-CDs enhanced photosynthesis (55.3 %) of maize under drought stress, and the full life cycle study showed that Soy-CDs can promote the metabolism of maize kernels, ultimately improve the yield (40.5 %) and nutritional quality of maize. Therefore, this work discovers the enormous potential of biomass-derived carbon dots in improving drought resistance and quality of crop, which contributes to ensure food security.