Electron-microscopic-histochemical demonstration of succinic-dehydrogenase activity in root cells of yellow lupine.

Succinic dehydrogenase (SDH) activity was demonstrated in unfixed root segments from Lupinus luteus at the ultrastructural level by the use of ferricyanide as electron acceptor. The specificity of the reaction was proven by malonate inhibition. The reaction product was found to be localized in the mitochondria and to a lesser extent on the membranes of plastids. Different mitochondria of the same cell often showed different intensity of the staining reaction. Different cells of the same tissue exhibited varying degrees of enzyme activity. An increase was found in the number of cells exhibiting the SDH reaction, as well as in the intensity of the reaction itself, from the meristematic zone of the root to the more differentiated regions.