Using glycotechnology procedures, structural changes in asparagine-linked sugar chains (N-glycans) of glycoproteins in Ricinus communis seeds during dedifferentiation (callus induction) have been explored. N-Glycans were released from the glycoproteins in the 2,4-D derived callus tissues by hydrazinolysis, and the resulting oligosaccharides were N-acetylated and coupled with 2-aminopyridine. Structures of the purified pyridylaminated (PA-) N-glycans could be deduced by two-dimensional (2D) sugar chain mapping method. Structural analysis clearly showed that the relative amount of high-mannose type N-glycans of the endospermic glycoproteins decreased as the plant cells dedifferentiated, while that of complex type N-glycans increased. this observation suggested that enhancement of expression and/or activation of certain α-mannosidase(s) involved in N-glycan processing could occur during dedifferentiation of plant cells.