Unveiling the key toxicity indicators and mechanisms on phytotoxicity of cerium dioxide nanoparticles in rice (Oryza sativa)

The splendid varieties of cerium dioxide nanoparticles (nCeO₂) and their diverse applications stimulated their uncontrolled discharge in the biological system. So, in the present study, Oryza sativa was adopted as a model plant and its phytotoxic effects were studied with neutrally charged, >12 nm sized spherical nCeO₂ (0 g/L, 2 g/L, 4 g/L, 6 g/L, 8 g/L & 10 g/L). The studies were also conducted with bulk ceria counterparts and compared. This work is focused on a systematic approach to evaluate the phytotoxicity of nCeO₂ in Oryza sativa, in terms of key toxicity indicators, nanoparticle uptake, and aggregation mechanisms. With this study, we propose a new sensing approach with non-fluorescent/non-chemiluminescent molecules for the detection of the generation of reactive oxygen species (ROS) to study the mechanism of phytotoxicity. An aggregation mechanism was also detailed to explicate the ROS-induced phytotoxicity. The study demonstrates that an increase in the production of ROS causes progressive cellular damage in Oryza sativa only at lower exposure level concentrations of nCeO₂ (≥4 g/L). Our findings revealed that the key toxicity indicators and the actual nanoparticle uptake and aggregation mechanisms will decide the extent of phytotoxicity of nCeO₂ in Oryza sativa.