Ecotoxicological effects of individual and combined treatments of chlortetracycline and oxytetracycline on seed germination and seedling growth of wheat (Triticum aestivum L.).

A significant issue facing the world today is the antibiotics pollution of agroecosystems. Chlortetracycline (CTC) and oxytetracycline (OTC) are frequently detected antibiotics in soil. However, little is known about their ecotoxicological effects on crops. Here, the potential adverse effect of CTC and OTC individually and in combination on germination, growth, antioxidant enzyme, malondialdehyde (MDA), chlorophyll, and soluble protein (SP) in Triticum aestivum L. grown in soil contaminated with 1, 10, and 50 mg (CTC and/or OTC) × kg^-1 of soil was tested. The results showed that low concentrations (1 mg·kg^-1) of CTC, OTC, and combinations of antibiotics (CA) promoted seeds germination and root elongation, which were inhibited by high concentrations (50 mg·kg^-1) of CTC or OTC. CTC and/or OTC-exposure significantly reduced plant heights, with OTC having the most pronounced effects. Biomass accumulation was not evidently influenced by CTC or OTC but was significantly increased by their mixture. Peroxidase, superoxide dismutase, catalase activity, and MDA level increased with elevated CTC and/or OTC concentrations, indicating oxidative damage to wheat. Chlorophyll, carotenoid, and SP were decreased by exposure to low concentration of CTC and/or OTC but were slightly increased with the increase in concentration. Integrated biomarker response (IBR) analysis indicated CA (IBR = 13.00) had the most profound impact, followed by CTC (IBR = 12.49) and OTC (IBR = 11.97) had the least influence at the highest concentration (50 mg·kg^-1). These results contribute to a deeper understanding of the physiological toxicity of CTC and oxytetracycline alone and in combination on wheat and provide a basis for further assessment of their potential ecological risks.