Vacuum-Microwave Combination for Processing Plant Tissues for Electron Microscopy

Preparation of botanical specimens for electron microscopy (EM) is hampered by several physical factors unique to plant cells. Impediments to penetration and action of various reagents in the tissue preparation process include the vacuole, plastids, cell wall (CW), and intercellular air space (Roland, 1978 ; O’Brien and McCully, 1981 ; Roland and Vian, 1991 ; Ruzin, 1999 ). The vacuole is a membrane-bound, fluid-filled sac that typically occupies more than 80% of the cell volume (Fig. 1 ). The plastids are double-membrane-bound organelles, which, like the vacuole, occupy a large percentage of cell volume (Fig. 1 ). Both of these cellular components contain an appreciable volume of fluid and may also contain large concentrations of solutes. Release of their contents during processing can affect fixation, by locally diluting the fixative solution, shifting the pH of processing solutions, or increasing the solute concentration in the vicinity of the tissue.