Effects of ciprofloxacin on turion germination and seedling development in two submerged aquatic plants

Abstract Germination and seedling development are crucial processes for plant growth and survival, and asexual propagules are predominant reproduction organs for aquatic plants. Ciprofloxacin is widely detected in both terrestrial and aquatic ecosystems, while studies on its effects on germination and seedling development mainly focused on terrestrial plants. We evaluated effects of ciprofloxacin (0.1, 1, 5 and 10 mg/L) on turion germination and early establishment of two submerged plants species (Potamogeton crispus and Hydrilla verticillata). Results showed that germination rate and rooting rate of both species were not impacted by ciprofloxacin. However, 0.1 mg/L ciprofloxacin significantly accelerated germination of H. verticillata and 5-10 mg/L ciprofloxacin significantly delayed rooting of both species. With rising ciprofloxacin concentrations and prolonging exposure time, seedling tolerance index and root number of both species decreased significantly, and shoot number decreased slightly in P. crispus but kept increasing in H. verticillata, suggesting better tolerance of H. verticillata under ciprofloxacin exposure. Root and shoot biomass accumulation, photosynthetic pigments contents of both species were all significantly inhibited. To defense against oxidative stress and prevent lipid peroxidation, antioxidants of both species including superoxide dismutase, catalase, guaiacol peroxidase, polyphenol oxidase, ascorbate peroxidase, ascorbic acid, reduced glutathione were activated to varying degrees. By integrating biomarker responses, we found the stress degree of ciprofloxacin on seedlings of both species was enhanced with increasing ciprofloxacin concentrations. Overall, ciprofloxacin impacted turion germination process and harmed early establishment of both species, suggesting potentially adverse effects of ciprofloxacin pollution on survival and expansion of submerged aquatic plant populations.