Effects of different epoxies on avoiding wrinkles in thin sections of botanical specimens

Abstract

Folds or wrinkles appear frequently in thin sections cut from botanical material embedded in epoxy resin such as Epon 812 (Polysciences) or EM-bed-812 (Electron Microscopy Sciences). Small wrinkles may occur more or less perpendicular to the cutting direction and mostly across the cell wall, causing problems in the examination of the ultrastructure. We studied the occurrence of wrinkles and folds by methodological sectioning, with regard to block hardness, use of Formvar-support film, and chloroform vapor. Methodological sectioning or changing the block hardness did not reduce the occurrence of wrinkles in sections. Chloroform vapor improved the result as did also the use of uncoated grids. Wrinkles and folds could be avoided completely by embedding the specimens in LX-112 (Ladd) or ERL-4206 (Polysciences) lowviscosity epoxy resins, in which case Formvar-coated grids could be used, and chloroform vapor was not necessary.

A study of section wrinkling on single‐hole coated grids using TEM and SEM

“…A relation between specimen type and wrinkle formation seems to be implied by the fact that some specimens rarely have wrinkles whereas others always have severe wrinkles (Pikakaski and Suoranta, 1985). Thin sections of biological material do not have uniform density.…”

“…However, studies involving serial sectioning or low-magnification or stereological studies do not carry this option, and the use of a single-hole grid with supporting film is imperative. In the study of Pikakaski and Suoranta (1985), low-viscosity epoxy resin was recommended to eliminate the wrinkles. The use of low-viscosity resins such as Spurrs (Spurr, 1969) and Quetol 651 (Kushida, 19741, however, do not eliminate the problem from many specimens.…”