Ecotoxicological relevance of nano-NiO and acetaminophen to Hordeum vulgare L.: Combining standardized procedures and physiological endpoints.

The present work aimed to assess the ecotoxicological relevance of acetaminophen (AC) and nickel oxide nanomaterial (nano-NiO) to barley plants. Combining standard procedures and several biochemical determinations, a global approach regarding the biological effects of these two contaminants was performed. After 14 days of growth, the exposure of barley to increased concentrations (0, 87.8, 131.3, 197.5, 296.5, 444.4, 666.6, and 1000 mg kg(-1)) of each contaminant resulted in a marked decrease in biomass production and biometric parameters. Photosynthetic pigments and markers of oxidative stress were analyzed to assess if any of the treatments interfered with the physiological performance and with the cellular redox state. Our observations revealed that only nano-NiO induced a negative response in total chlorophylls and carotenoids, confirming the macroscopic phytotoxicity symptoms (chlorosis). However, both contaminants led to a significant increase in lipid peroxidation (LP), superoxide anion (O2(.-)), and cell death for all the tested concentrations, suggesting that AC and nano-NiO cause oxidative stress in barley, even at the lowest applied dose (87.8 mg kg(-1)). Comparing the two studied approaches (parameters included in standard protocols and several biochemical determinations), it is concluded that the inclusion of several biochemical endpoints, especially those related to oxidative stress, resulted in a more sensitive analysis and thus, a more sensitive risk evaluation of these two contaminants for barley plants.