Copper (Cu) is a transition metal which has two oxidation states under physiological conditions.As a result, Cu is the cofactor of numerous enzymes involved in electron transfer reactions.However, Cu excess is highly toxic because it catalyses Fenton reactions which generate hydroxyl radicals causing damages to lipids, proteins and DNA.In this study, Cu specificly induced initiation of lateral root in wild-type seedlings, but had little effect on initiation of lateral root in Atga1 mutant.