Advantages of the use of intact plant tissues in freeze-fracture electron microscopy.

The use of whole, intact plant tissue for freeze-fracture electron microscopy provides important information that cannot be obtained from the use of isolated biological membranes or of artificial (phospholipid) membrane preparations. This is not to imply that these examinations of such preparations are not useful, since it would be difficult to interpret our observations of intact cells and tissues without the analysis of these model systems. Analysis of intact tissue and cells reveals the relative densities of membrane proteins of the different membranes within a cell; the three-dimensional organization of various organelles, especially the endoplasmic reticulum; changes in intramembranous particle (IMP) distribution due to stress or injury; and, in conjunction with the use of filipin, membrane sterol content and relative distribution. It is our intention that this survey of freeze-fracture images of intact plant tissues will illustrate the uniqueness of the information gained from an analysis of whole plant tissues compared to isolated membrane fractions.