Mitigation of heavy metal toxicity in tomato (Solanum lycopersicum L.) plant using green-synthesized cerium oxide (CeO₂) nanoparticles

This study was aimed at synthesizing cerium oxide nanoparticles (CeO₂ NPs) from pulp extract of dates (Phoenix dactylifera) and to understand their effect on photosynthetic and antioxidant properties of tomato (Lycopersicon esculentum L.) plants under copper (Cu) stress. The produced CeO₂ NPs were validated by XRD analysis, and the average crystal size of the NPs was estimated at 11 nm. Ce–O stretching vibration at 712 cm⁻¹ reflected in FTIR analysis confirmed the formation of cubic nanoceria. TEM analysis was used to ascertain the size and morphological details of the produced NPs, which were spherical-shaped and polydisperse. A pot experiment was performed to evaluate the plant's different parameters at various phases. The experiment involved the application of foliar treatments of varying concentrations of CeO₂ NPs (50, 100, and 150 ppm) at 15–17 days after transplant (DAT). Sampling took place at 45 DAT to assess different parameters, whereas yield traits were determined at 60 DAT. The results indicates that CeO₂ NP application mitigates Cu stress by increasing chlorophyll content, photosynthesis, and gas exchange parameters in tomato plants, further boosting growth and yield traits. Furthermore, CeO₂ NPs enhanced the activities of enzymes involved in photosynthetic and biochemical reactions in tomato plants with and without Cu stress. Specifically, CeO₂ NPs treatment played a crucial role in maintaining redox homeostasis by balancing reactive oxygen species (ROS) levels and the antioxidant defence system. Based on our findings, the ideal concentration of CeO₂ NPs was 100 ppm, which showed the best results of the various concentrations examined. This study presents a breakthrough in green nanotechnology, where plant-derived CeO₂ NPs act as bio-safe growth stimulators to counteract Cu stress. With proper scaling and commercialization, these nanoparticles (NPs) could be a key innovation in sustainable nano fertilizers, bioremediation techniques, and precision farming solutions.