Electron Microscopy and Plant Ultrastructure

• Main Author: Robards, A. W. Anthony Williams (Author)
• Format: Book
• Language: English
• Published: London McGraw-Hill 1970; ©1970
• Series: European plant biology series
• Subjects: Electron microscopy > Technique; Plant cells and tissues
• Online Access: Click Here to View Status and Holdings.

 One of the dangers of an instrument which produces such meaningful and important results as the electron microscope has done during the past few yea is that the value of the apparatus sometimes tends to become overestimated relative to other contemporary techniques. It is easy to concentrate on the vil of electron microscopy while neglecting the still important role of the ligh microscope. For most biological material, maximum information is obtained by employing light and electron microscopy jointly. A notable exception i course, in the study of viruses which are normally too small to be resolved by the light microscope. Electron microscopy is not a means of research to be undertaken lightly, are the results open to such simple interpretation as may at first glance seem possible. Limitations imposed by the instrument itself, as well as by treatment of the specimen to be viewed, make us constantly aware that results of value are only obtained after most careful and patient interpretation of micrographs in the light of the methods whereby they have been produced. To exemplify this, let us consider how best the structure of a unicellular alga could be studied. Using the light microscope, it would be possible to observe the living cells directly using phase-contrast or normal optics. Chemically fixed material could be examined, and cytochemical studies would be possible, so presenting to the best advantage various aspects of cellular structure. As such methods would be undertaken using a microscope having the same resolving power, all observations could be directly related to the pictures of living cells. Turning to electron microscopic observation, the cells would be much too large to observe intact as electrons would not be able to traverse such a thickness of material. In any case, the cells need to be completely desiccated before they are put into the high vacuum of the specimen chamber. This means that, if any hope is to be held for obtaining a micrograph which may be useful in interpreting the original, living. material, then cells must be 'fixed' in such a manner as to preserve them in a form as close to the natural state as possible. After dehydration so that they may be placed into high vacuum without fear of rapid, disastrous, desiccation, the cells are embedded in some hard plastic, sectioned, and only then viewed in the microscope. Even when the specimen is safely in the microscope, changes may be introduced in many ways, ranging from the effect of high vacuum, the bombardment of the specimen with electrons, and contamination of the specimen with carbon, to distortions and aberrations introduced by the electron optical system itself.