Phytotoxicity and degradation of antibiotic ofloxacin in duckweed (Spirodela polyrhiza) system

Abstract The phytotoxicity and degradation of ofloxacin (OFX) in duckweed Spirodela polyrhiza based system was estimated in this study. For that, OFX was added in an environmentally relevant range (0.01–1.0 mg L −1 ) in medium (Hoagland nutrient) and toxicity biomarkers, i.e. changes in plant biomass, relative growth rate (RGR), photopigment (Chl- a , Chl- b and carotenoids), protein content, antioxidative enzymes (catalase, CAT; superoxide dismutase, SOD; and ascorbate peroxidases, APX) in fronds were estimated. The batch-scale setups (250 ml) was prepared in triplicate for each concentration of OFX and reared in growth chambers (Algae Tron AG 230) for 7 d. Results suggested that the high concentrations of OFX caused a reduction in biomass (4.8–41.3%), relative root growth (RGR), protein (4.16–11.28%) and photopigment contents. The fronds in OFX spiked setups showed an increased level of antioxidative enzymes: CAT (0.230–0.338 mmol H2O2 mg −1 protein), APX (0.043–0.074 mmol ascorbate mg −1 protein), and SOD (0.267–0.317 U mg −1 protein) than control. At the end (7 d), the residual OFX content in the medium was also estimated, and results suggested a significant ( p