Effects of hydration on the surface morphology of urediospores

Changes in the surface morphology of mature urediospores of Uromyces viciae-fabae have been studied with respect to different preparative procedures for the scanning electron microscope. Specimens were examined in the critical point-dried, freeze-dried and frozen-hydrated states. Dried urediospores were significantly different in appearance from those which were hydrated. Shrinkage probably accounted for some of the surface features of dried spores, particularly amongst those which had been critical point-dried. No significant effects on spore surface texture resulted from chemical immersion fixation, chemical vapour fixation, dehydration or the mode of sputter-coating. It is suggested that the presence or absence of unfreezable water, involved in maintaining the structural stability of polymers which provide the specimen surface with its characteristic morphology, may have an important influence on the gross texture of cell surfaces as viewed with the scanning electron microscope.