Abstract: When the exposed surface of the girdled trunk of Eucommia ulmoides Oliv. were daubed with plant hormones, i.e. ethrel, 2,4-D, NAA, GA and NAA+GA respectively in appropriate concentrations, it was found that the 2,4-D, GA and NAA+ GA treated trunks, initiations of phellogen and vascular cambium in callus were earlier than that in control. These trunks treated with ethrel, formation of phellogen alone were earlier. However, initiation of phellogen and differentiation of vascular cambium in the trunk treated with NAA were similar to control.

Key words: Exogenous hormones, Bark regeneration, Eucommia