CdS nanoparticles may disrupt nitrogen and carbon metabolism in spinach (Spinacia oleracea L.) through different exposure pathways

Cadmium (Cd) contamination is a significant global environmental issue due to its toxic effects on plant and human health. However, the specific impacts of cadmium sulfide nanoparticles (CdS NPs) on plants, including the underlying molecular mechanisms, toxicity, uptake, and accumulation, remain poorly understood. This study explored the influence of CdS NPs on spinach plants by combining phenotypic and metabolomics analyses. Spinach plants were exposed to CdS NPs (0.005, 0.01, 0.2, 0.4, and 1 mg/L) and Cd ions (0.1 mg/L) through foliar and root for three weeks. Results indicated that root exposure had a more pronounced impact on biomass, plant height, leaf structure, and chlorophyll content than foliar exposure. Cd and CdS NPs uptake in root and shoot were confirmed through Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy-Dispersive X-ray Spectroscopy (EDS), respectively and/or jointly. Metabolomics analysis revealed that CdS NPs altered nitrogen metabolism, carbon metabolism, tyrosine metabolism, and isoquinoline alkaloid biosynthesis, which are crucial for plant growth, development, and survival. These findings enhance comprehension of the intrinsic phenotypic and metabolic alterations induced by CdS NPs in spinach plants.