Practical Aspects Of Quantitative Feulgen Staining In Plants
J Greilhuber and EM TemschUniversity of Vienna, Institute of Botany, Vienna, Austria
The past six years have experienced the decline of the idea of the plastic genome. Improved techniques of measurement have demonstrated the non-existence of previously-claimed genome size variation in taxa such as Pisum sativum, Glycine max and Arachis hypogaea. Nevertheless, data are accumulating that show some amount of intraspecific genome size variation in wild plants. It is not often clear from the publications whether methodological rules have been stringently applied or not. At the same time, the negative effect of secondary plant metabolites such as flavanols on the precision of plant DNA measurements becomes more and more obvious. Therefore, more critical methodological studies are urgently needed.
Here we address some questions relevant to best practice in quantitative Feulgen staining in plants. These questions relate to (1) the optimal performance of the Feulgen procedure with special reference to practice, and (2) the recognition of disturbing influences of secondary plant metabolites on the outcome of the Feulgen reaction for DNA. Both points have significance, among others, for field work directed towards genome size studies. For instance, there was no publication analysing the decay of fixed material over time at various temperatures. Or, the previously underrated frequent occurrence of chromatin-binding secondary plant metabolites, which impair Feulgen staining, makes a reconsideration of the current practice of standardisation necessary. An experiment is described which can point to the presence of such substances in the material of interest. Eighty years after the invention of the Feulgen reaction1 many questions on best practice are still open.
1Feulgen R, Rossenbeck H. (1924). Z. Physiol. Chem. 135: 203-248.