CHAPTER 3 

 CONFIRMATORY STUDIES OF 

 LIGHT MICROSCOPIC OBSERVATIONS 



Introduction 



Light microscopy has proved to be very useful in 1 ) 

 viral diagnosis and classification, 2) the selection of 

 tissues for ultrastructural studies, 3) monitoring host 

 tissues for virus infections, and 4) monitoring viral 

 inclusion purification (Christie and Edwardson, 1977; 

 Hiebert et al. , 1984). The large field of view, the 

 chemically selective stains, and the speed and ease of 

 tissue preparation and examination are some of the 

 advantages of light microscopy over electron microscopy in 

 studying viruses. In the second chapter, the use of light 

 microscopy for the diagnosis of orchid viruses has been 

 described. However, the resolution of light microscopy is 

 limited. In recent years, the demands for comparative 

 light and electron microscopic studies of individual cells 

 or specific tissue structures has led to the development 

 of various procedures which permit examination of the same 

 tissue area by both types of instrument (Rossi et al_. , 

 1972; Nilsen et al_. , 1982; Perrie and Webb, 1982). In 

 this study, modified electron microscopic methods are used 

 to reveal the fine structure of viral inclusions whose 



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