Mechanism for Plant Cellular Morphogenesis.

The control of the cylindrical cell form in plants appears to reside in the orientation of the reinforcing cellulose microfibrils in the side walls. In elongating cells the fibrils are typically transverse. Control of new synthesis of oriented wall texture is shown to be in turn related to the orientation of cytoplasmic elements in the cell periphery. Three properties of these cytoplasmic elements have been deduced from polarization optical properties of treated and normal cell walls. These deduced properties- namely, possession of a long axis and the ability to build microfibrils perpendicular to it, a tendency to cross-bond to make a parallel array, and a sensitivity of this alignment to colchicine-are all well-known properties of mitotic spindle and phragmoplast fibers which form the cross-wall after mitosis. It is proposed that proteins of spindle fiber nature exist in cortical cytoplasm of plant cells and are active in the control of wall texture and cell form.