CDs alleviate oxidative stress in tomato seedlings under water deficit stress

Drought severely impairs plant growth and crop yield, thereby posing a substantial threat to global food security. Conventional drought resistance strategies typically depend heavily on freshwater resources, which exacerbates the conflict between water allocation for human consumption and agricultural use. Nanomaterials, endowed with unique properties such as a large specific surface area and high catalytic activity, can modulate plant growth and stress tolerance by improving cellular microenvironments or interacting directly with key biochemical processes. This study identifies citric acid-formamide carbon dots- a type of carbon based nanomaterial hat enhances drought stress resistance in tomato plants (Solanum lycopersicum): root application of CDs increased seedling height, as well as fresh and dry biomass, alleviated drought-induced growth inhibition, reduced chlorophyll degradation, and improved photosynthetic efficiency; mechanistically, experimental evidence demonstrated that CDs are primarily taken up by tomato roots via active transport and the apoplastic pathway, transcriptomic analysis revealed significant differential expression of 156 genes (including those involved in oxidative stress response regulation), in vitro co-incubation assays showed CDs reduced levels of reactive oxygen species (ROS; i.e., H2O2 and O2-), and consistently, CDs decreased ROS accumulation in excised tomato leaf discs and further reduced H2O2, O2-, and malondialdehyde (MDA) accumulation in intact tomato leaves under drought. Notably, foliar application of CDs also alleviated drought stress. Collectively, these results indicate that CDs possess intrinsic ROS-scavenging activity, which reduces drought-induced ROS overaccumulation and thereby enhances tomato drought tolerance, providing novel insights into nanomaterial-plant interactions and a potential strategy to mitigate drought-associated crop yield losses.