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New technique--new insights, inside and out
How often in science do we see that the development of a new technique opens up new areas of research? Indeed, some new techniques, such as recombinant DNA technology and PCR have had very major effects. That is not to say that all technical innovations have such a dramatic an impact on science, but nevertheless new techniques nearly always add to our investigative ability. Thus, Donald et al. (Cambridge and Norwich, pp. 73-77) describe the application of environmental scanning electron microscopy (ESEM) to the study of living plant tissues. In conventional SEM the sample chamber is evacuated; under high vacuum some specimens become distorted. In ESEM, the chamber is not under vacuum: it contains gas that can be, as described by the authors, water vapour. Thus, in plant tissue, turgor may be controlled. Further, the ionization of the gas by the electrons removes the need to coat the sample with a layer of conductive material. The authors then show how the ESEM may be used to study cellular and tissue responses to stresses applied by a tensometer. Cell and tissue breakage are important in normal developmental processes such as abscission and seed shedding but may also occur because of environmentally derived damage or stress. In the ‘model’ system described here, the onion epidermis was treated with a chelating agent (thereby weakening the middle lamella); stressing the tissue caused the cells to separate without losing their turgor (implying that broken plasmodesmata along the fracture surface were sealed). However, when a notch was cut in the tissue, individual cells were ruptured along the line of a tear that extended from the point of the notch when the tissue was stressed. These observations could not be made in real time on living tissue with the conventional SEM, thus showing the potential of this new technique.
Professor J. A. BryantUniversity of Exeter, UK
j.a.bryant{at}exeter.ac.uk
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