Scanning Electron Microscopy


Various scanning electron microscopy preparative techniques have been used by researchers to examine sectional views of dry, mature soybean (Glycine~ CL.) Merr.) seed coats. Such previously employed techniques were utilized In our preliminary investigations of seed coat structure, but often yielded unacceptable preservation. Consequently, eight preparative techniques were evaluated In an effort to define conditions required to obtain consistently high quality preservation of soybean seed coats In sectional view. Of the eight procedures tested with the cultivar Williams 82, razor sections and mechanical fractures of dry seed coats yielded the poorest definition of anatomical features. Samples soaked In water prior to preparation and those subjected to prolonged osmium fixation showed unacceptable alteration of the seed coat parenchyma. Best preservation was obtained with seed coats which were not subjected to chemical fixation, but which were sequentially dehydrated from 20% ethanol, cryofractured, and critical point dried. Results obtained via this protocol, with four additional soybean genotypes and cultivars, demonstrate Its applicability to comparative anatomical analysis.

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