In defence of aldehyde—osmium fixation and critical‐point drying for characterization of seed‐storage fungi by scanning electron microscopy

Low-temperature scanning electron microscopy cannot be used as a general approach when resolution of definitive surface features is required for fungal characterization, because of the production of a pervading exudate by some of the species, strains or varieties. As the resolution of the light microscope is obviously limiting, scanning electron microscopy remains the best microscopical mode. Results are presented for four species within the Aspergillus flavus group which indicate that minimal (if any) distortion or collapse can be achieved with concomitant preservation of surface morphology, when particular precautions are taken during fixation and critical-point drying. Details of the steps pertaining to preparation for scanning electron microscopy following critical-point drying that are considered collectively to contribute to the success of the approach are discussed.