Monitoring cell-wall formation in vivo with Fluorescent Brightener 28, by fluorescence microscopy, revealed that tobacco protoplasts regeneration started within 30 min indicated by cellulose microfibril formation at distinct sites on the protoplast surface. Oriented cellulose microfibril deposition was apparent before elongation and indicated the early polarization of protoplasts. The sequence of cellulose microfibril deposition correlates with an helicoidal-like texture. Within 6 h, a texture was completed. Tobacco suspension cells, stained by decolourized aniline blue, showed radiant granular callose fluorescence in cell plates and transverse walls. During the culture cycle of suspension cells, transverse fibrillar deposits of callose gradually appeared in the lateral walls during the log-phase, and subsequently disappeared in the early stationary phase of the cell culture. Similar callose transitions were observed in regenerated elongating protoplasts. Culture cells ofMorinda citrifoliaL. only showed transient granular depositions in the lateral walls. The callose formations did not result from artificial wounding. The transient appearance of callose might be related to cellulose microfibril deposition.Keywords: aniline blue, Calcofluor White ST, callose, cellulose, Fluorescent Brightener 28,Morinda citrifolia,Nicotiana tabacum.