The nanoparticles influence on plants’ biological processes has not been clearly understood. Increase of nanoparticles in the environment during advent of industrial technologies can be a significant threat to ecosystems, and their interaction with plants is very important. The aim of this study was to investigate the effects of cerium oxide nanoparticles (CeO2 NPs) on biochemical and physiological parameters of marigold (Calendula officinalis L.). (389 characters)