The Effect of Preparation Techniques on Sem-Imaging of Pit Membranes

Abstract

This paper examines the effects of 30 preparation techniques on SEMimages of pit membranes in vessels and tracheids from the two latest growth rings in twigs of Pinus wallichiana, Fraxinus americana and Laurus nobilis. Most variation observed is due to coating and treatment with chemical solutions, such as acetone, ethanol and hydrogen peroxide. The effects of chemicals appear to be associated with the thickness of the pit membrane, resulting in an increased density and diameter of pores in pit membranes of F. americana and L. nobilis and an almost complete dissolution of the porous margo in P. wallichiana. Although different protocols offer advantages for different species, the following methods are recommended: (1) the use of fresh material, (2) air-drying without any chemical treatment, (3) splitting of dried samples, (4) vacuum evaporation with platinum, and (5) SEM-imaging at an accelerating voltage below 5 kV.