It was found in the present study that redifferentiation frequency of callus in E.ulmoides could be raised remarkably by adding an appropriate concentration of PEG in the basal medium.In doing so,whats worth particular attention was as follows:the effect of PEG on promoting shoot redifferentiation was closely related to the molecular weight of PEG,and the concentration of PEG in basal medium.It was also related to the strength of inorganic ions,and the concentration of sucrose in the medium.The most ef...