Acclimation of soybean in saline-alkali soil by reactive oxygen species-scavenging carbon dots supplemented with calcium ions

This is the authors' abstract. We don't add key points for this paper.

: Carbon dots (CDs) possessing reactive oxygen species (ROS) scavenging activity have emerged as promising agents for enhancing plant tolerance to salt stress. However, their potential in saline-alkali soils has received limited attention. Furthermore, although metal-doped CDs have been explored, the comparative efficacy of chemically modified versus physically mixed metal-CD formulations remains unclear. Herein, we demonstrate that lysine-derived carbon dots (LysCDs) physically combined with calcium ions (Ca 2+ +LysCDs) confer superior benefits to soybean under saline-alkali stress compared with chemically conjugated Ca 2+ /LysCDs. Despite comparable ROS-scavenging capacities in vitro, the two formulations differed markedly in surface charge: Ca 2+ +LysCDs exhibited a negative zeta potential, whereas Ca 2+ /LysCDs showed near-neutral surface charge. This difference in surface charge likely modulates root uptake efficiency, thereby affecting intracellular ROS clearance and the activation of downstream signaling cascades governing ion homeostasis and antioxidant defense. In addition, Ca 2+ +LysCDs amendment more effectively improved the rhizosphere soil environment, as reflected by increased activities of urease and dehydrogenase and the selective enrichment of plant growth-promoting rhizobacteria. Collectively, these findings offer a framework for the rational development of CD-based soil amendments tailored to improve crop resilience in saline-alkali environments.