Antibiotic pollution has become an important global issue, and ofloxacin (OFL) is widely used worldwide. However, little is known about the potential adverse effects of OFL on plants. We assessed the toxic effects of OFL on Welsh onion and explored its toxicity mechanism. The leaf pigment content increased in 0.1 mg/L of OFL but decreased in a dose-dependent manner (0.5-2 mg/L OFL) until leaf etiolation. The ultrastructure of leaves showed that the treatment of 2 mg/L OFL produced significant toxicity. Furthermore, photosynthetic and fluorescence parameters were negatively affected by OFL treatment. The photosynthetic electron transport chain was significantly inhibited by OFL treatment, especially between QA and QB. The hydrogen peroxide and malondialdehyde content also increased with OFL concentration, indicating that antioxidant enzymes' role in antibiotic response is limited. In conclusion, OFL can damage chloroplasts by promoting ROS accumulation, which results in the etiolation of Welsh onion leaves.
Keywords: Antioxidant enzymes; Electron transport; Ofloxacin; Photosynthesis; Welsh onion.
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