CHAPTER 4 

 CONCLUSIONS 



Light microscopy using the Azure A and 0/G stain was 

 shown to be a useful diagnostic tool for some orchid 

 viruses. For orchid viruses which cannot be detected by 

 conventional methods (bioassay, leaf dip electron 

 microscopy and/or serology), this technique is the only 

 practical alternative for this purpose. It also has the 

 advantage of being fast and inexpensive. It is an 

 important technique for developing countries which cannot 

 afford expensive facilities. In addition to diagnosis, 

 this technique is very useful in the selection of tissues 

 for ultrathin sectioning, for monitoring viral inclusion 

 purification, and the selection of antisera for 

 identifying the specific level of viruses (Christie and 

 Edwardson, 1977; Hiebert et al., 1984). 



Orchids posed several problems which had to be 

 overcome to make the light microscope techniques 

 successful. For thick-leaved orchids, paradermal sections 

 could be conveniently made, whereas, for thin-leaved 

 orchids, sandpaper abrasion was preferable to expose cells 

 for staining. For instances where cell walls were 

 exceptionally thick, heating at 60 C was necessary to 



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