1985 by CRC Press, Inc. Plant protoplasts provide a unique system for studying the structure, chemistry, and function of cell organelles. One of the major advantages of using protoplasts is the relative ease with which they can be lysed by gentle techniques such as osmotic shock or the application of mild detergents and poly-cations. Organelles can be isolated without using the harsh mechanical methods necessary for disrupting plant cells. Isolation of many cell organelles has been achieved using plant protoplasts (see reviews by Quail,1Fowke and Gamborg,2and Galun3).