Cerium oxide nanoparticles enhance rice productivity by modulating nitric oxide signaling, carbon metabolism, and potassium homeostasis under chromium-induced environmental stress

Chromium (Cr) contamination in agricultural soils represents a serious challenge to rice productivity and food security, underscoring the need for innovative approaches to improve Cr-tolerance and alleviate its detrimental effects on plant growth and development. Recently, nanotechnology has been increasingly used to improve the tolerance of plants exposed to metal stress. In view of the beneficial roles of nanoparticles in mitigating metal stress in plants, this study was conducted to assess the effectiveness of cerium dioxide nanoparticles (CeO 2 NPs) in alleviating Cr-induced toxicity in rice plants. Chromium stress (100 µM) and CeO 2 NPs (100 ppm) were applied at the seed stage by soaking the seeds in their respective solutions for 12 h prior to sowing. Chromium stress markedly increased the contents of thiobarbituric acid-reactive substances (TBARS) by 67%, hydrogen peroxide (H 2 O 2 ) by 62%, superoxide anion (O 2 • - ) by 58%, and methylglyoxal (MG) by 63% compared with control plants. In contrast, Cr stress significantly reduced the concentrations of starch (51%), sucrose synthase (49%), amylase (68%), chlorophyll (69%), and RuBisCO (67%). However, the application of CeO 2 NPs markedly enhanced plant growth and biomass accumulation, alleviated oxidative stress, and stimulated antioxidant enzyme activities in rice plants subjected to Cr stress. Overall, these results demonstrate that the application of CeO 2 effectively alleviates Cr-induced stress in rice plants and offers promising prospects for advancing NP-based phytoremediation strategies.