Evaluation of cerium oxide nanoparticles' effects on pakchoi (Brassica chinensis L.) based on metabolomics analysis

Nanotechnology holds significant potential for agricultural applications, yet plant response mechanisms to nanoparticle exposure remain poorly characterized. Cerium oxide nanoparticles (CeO₂ NPs), prevalent in commercial products, were investigated using soil-grown pakchoi (Brassica chinensis L.) exposed to 0.5, 5, 50, and 250 mg kg^-1 doses. Physiological and metabolic analyses revealed that CeO₂ NPs reduced photosynthetic intensity (31 % chlorophyll decline at 5 mg kg^-1) while increasing CO₂ absorption (26 %-46 % elevated stomatal CO₂ across treatments). Lipid peroxidation remained unaltered at 5-250 mg kg^-1. Lysine reduction potentially restricted glutamate synthesis, ultimately decreasing proline by 83 % at 250 mg kg^-1. Concurrent metabolic perturbations included enhanced nitrogen assimilation, stimulated phenylalanine metabolism, increased δ-tocopherol, and disrupted methionine metabolism (dose-dependent decrease at high concentrations vs. increase at low concentrations). These findings decode pakchoi's response to CeO₂ NPs, which could help safer utilization of CeO₂ in the future.