There were only a few studies showing the effects of CuO NPs on seeds. Tomato seeds presented an increased root and shoot growth in lower concentrations of CuO NPs (20-200 mg/L), while higher concentrations caused a negative effect, possibly due to oxidative stress . Both shoot and root growth in lettuce appear to be negatively affected by CuO NPs if provided by foliar application . The data presented here mainly showed a positive effect for both species, which may be related to the application method and, perhaps, the consequence of faster germination.