Observations on Incomplete Cytokinesis in Callus Cells

Callus cells of Nicotiana, Oryza, and Pinus were observed to possess anomalies in the cytokinetic process. These alterations included: absence of cytokinesis with the formation of a binucleate cell, cell-wall formation at the periphery of the plate with a perforation near the central position of the anticipated wall, and cell-plate formation along the phragmoplast but with perforations at different positions in the new wall. Continuity of the plasma membrane existed through the pore between the daughter cells, and the large size of the pores provided for potential exchange of protoplasmic components between the cells. The occurrence of pores of variable size and at different positions along a wall may be related to the perforation or webbing of the phragmosome and the subsequent encirclement of these perforations with wall materials being deposited along the phragmoplast.