The impact of engineered nickel oxide nanoparticles on ascorbate glutathione cycle in Allium cepa L.

Engineered nickel oxide nanoparticle (NiO-NP) can inflict significant damages on exposed plants, even though very little is known about the modus operandi. The present study investigated effects of NiO-NP on the crucial stress alleviation mechanism Ascorbate-Glutathione Cycle (Asa-GSH cycle) in the model plant Allium cepa. Cellular contents of reduced glutathione (GSH) and oxidised glutathione (GSSG), was disturbed upon NiO-NP exposure. The ratio of GSH to GSSG changed from 20:1 in NC to 4:1 in roots exposed to 125 mg L-1 NiO-NP. Even the lowest treatments of NiO-NP (10 mg L-1) increased ascorbic acid (2.9-folds) and cysteine contents (1.6-folds). Enzymes like glutathione reductase, ascorbate peroxidase, glutathione peroxidase and glutathione-S-transferase also showed altered activities in the affected tissues. Further, intracellular methylglyoxal, a harbinger of ROS (Reactive oxygen species), increased significantly (~ 26 to 65-fold) across different concentrations NiO-NP. Intracellular H2O2 (hydrogen peroxide) and ROS levels increased with NiO-NP doses, as did electrolytic leakage from damaged cells. The present work indicated that multiple pathways were compromised in NiO-NP affected plants and this information can bolster our general understanding of the actual mechanism of its toxicity on living cells, and help formulate strategies to thwart ecological pollution. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01314-8.