Effects of cerium oxide nanoparticles on biochemical and oxidative parameters in marigold leaves

The effects of suspensions of cerium oxide nanoparticles sprayed onto marigold seedlings (Calendula officinalis L.) at concentrations between 50 and 3200 mg L-1 were studied. At concentrations of 50 and 100 mg L-1, the nanoparticles had a slight positive effect on some growth parameters, but at higher concentrations they caused severe oxidative damage. Activities of phenylalanine ammonia lyase and lipoxygenase increased from 400 mg L-1 upward, tyrosine ammonia lyase from 1600 mg L-1. Ascorbate and glutathione contents decreased from 400 mg L-1 upwards.