Protoplasts for Studies of the Plasma Membrane and Associated Cell Organelles

The plasma membrane forms a boundary between the living cytoplasm of the cell and the external environment and regulates the movement of materials (e. g. ions, sugars, amino acids) into and out of plant cells. Specific antigens and lectin binding sites are present on the outer surface of the plasma membrane and it has been suggested that the plasma membrane may also be involved in cellular recognition phenomena (e. g. Knox and Clarke 1978, Fowke and Gamborg 1980, Raff et al. 1980). Perhaps one of its most important functions is in the process of cell wall formation. During periods of active cell wall deposition, wall precursors are continually moved through the plasma membrane via exocytosis for assembly on the cell surface (Fowke and Gamborg 1980, Willison and Klein 1982). A number of cell organelles (microtubules, coated vesicles, actin microfilaments) are closely associated with the cytoplasmic face of the plasma membrane and may be involved in the process of cell wall deposition.