Targeted scavenging of hydroxyl radicals by biomass-derived carbon quantum dots in hydroponic and soil cultivation to enhance salt tolerance of mung bean

Removing reactive oxygen species (ROS) is critical for reducing plant salt stress. Although carbon dots (CDs) have been investigated in hydroponic systems, their use in soil remains limited, and the specific types of ROS they scavenge are not well defined. Here, biomass-derived CDs (F-CDs), synthesised from waste Flammulina velutipes roots, showed high selectivity and strong scavenging capacity for •OH. In hydroponic cultivation of mung beans, the F-CDs increased root length, stem length, fresh weight, and photosynthetic performance. Under saline hydroponic conditions, the F-CDs exhibited strong antioxidant properties that supported seed germination and seedling development. When applied to saline-alkali soil, the F-CDs increased the salt tolerance threshold for germination from 80 mM to 140 mM. Moreover, in soil mixtures with mild-to-heavy saline-alkali ratios of 3:1 or 1:1, mung bean seedlings showed markedly improved growth. These findings indicate that CDs hold considerable potential in nanotechnology for sustainable agriculture in salt-affected environments.