Processing plant tissues for ultrastructural study.

This chapter briefly describes conventional and microwave-assisted chemical fixation methods, as well as cryo-specimen preparation techniques for studying the cellular and organelle ultrastructure of plant tissues under transmission electron microscopy. The general methods and procedures for the plant specimen preparation (including fixation, dehydration, resin infiltration, and embedding) are similar to those for animal tissues. However, certain special characteristic features of plant tissues such as thick cellulosic cell wall, waxy substance in the cuticle, large amount of gases in the intercellular spaces, and the presence of vacuoles have created fixation and resin filtration difficulties. Specific modifications of the protocols used for animal tissues are therefore required, such as the application of vacuum during the initial fixation and resin infiltration stage to remove gases from the tissues and resin. Microwave-assisted procedure can reduce specimen preparation time, but both conventional and microwave-assisted chemical fixation procedures produce artifacts. Cryo-specimen preparation involves with high-pressure freezing and freeze-substitution can minimize artifact formation, but their application to highly vacuolated, thick-walled plant cells is limited.