Abstract:The localization of 6-benzyladenine in the callus cell of tobacco was studied by means of autoradiography. Electron microscope autoradiographs showed that the silver grains localized at not only cell membrane system such as plasma membrane, tonoplast, plastid membrane and mitochondrion membrane but also nucleus especially nucleolus. The results of the present study indicated that 6-benzyladenine receptor site associated with both cell membrane system and nucleus.