THE USE OF OSMIUM-THIOCARBOHYDRAZIDE FOR STRUCTURAL STABILIZATION ANDENHANCEMENT OF SECONDARY-ELECTRON IMAGES IN SCANNING ELECTRON-MICROSCOPY OF POLLEN

Pollen grains stained in a sequence of osmium (O) and thiocarbohydrazi de (T) solutions (collectively known as OTOTO) appear structurally sta ble and undistorted in the scanning electron microscope (SEM), and usu ally do not require special drying. In fact, OTOTO can be regarded as another special drying method in palynology. This sequential incubatio n also strikingly increases the electrical conductivity of pollen grai ns in the SEM. Compared to standard sputter-coating or vacuum evaporat ive procedures, OTOTO reduces charging and yields secondary electron i mages with significantly higher resolution.