Abstract: The surfaces of plant callus cells cultured in vitro from two species,Daucus carota and Nicotiana tubacum,were studied using scanning electron micrcoscopy. A number of spherical hemispherical protuberances or beads (papillary projections) in various sizes shapes occured on the outer surfaces of the callus cell walls. Most of the protuberances appeared with a sphercal bead on an irregular base projected on the cell wall surfaces and some of the larger bases were fused from two or more smaller ones. And adjacent projections could fuse also. Some of the spherical beads exhibited two clearly distinct regions, an upper region was distinct from the basal region by a granular appearence of margin,and a lot of the spherical beads or more flattened projections collapsed as a hollow at its top part might developed from these two part projections.A number of fibrils were seen to be associated with one or more of the projections on the surfaces of the carrot callus cell walls,and some of the cells coated with a fibrillar mat,but not all of the projections were associated with fibrils. And the fibrils or fibrillar mats were not seen on the surfaces of the more loosely packed tobacco callus cells.
The projections could fuse to form bridges between adjacent cells,and the fibrils could interlace intercellularly. Those observations might be taken as some evidence of initial adhesion between opposing cells from two unrelated calli after contact. The process of wall material secretion and its control were discussed.

Key words: In vitro culture, Cel1 surface, Wall material secretion, Cell adhesion

CLC Number: 

• Q248