Haem pigments of cytoplasmic particles from non-photosynthetic plant tissues

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Abstract
The haem compounds of white petioles of silver beet, roots of germinating wheat, flowers from spadices of "arum lilies" (Zantedeschia aethiopica) and apical stems of onion, were studied. Pieces of tissue, tissue dispersions and fractions separated by differential centrifuging were used. Low-dispersion microspectroscopes, a Beckman spectrophoto-meter and a General Electric self-recording Hardy-type spectrophoto-meter were used. The quantitative distribution of the haem compounds among the cytoplasmic particles of beet petiole was determined. The plant mitochondria contain cytochromes closely resembling in absorption spectra cytochromes, a, b, c and c1 of animal tissues. Cytochrome b is predominant. Cytochrome dh has not been detected in mitochondria from wheat roots or from silver-beet petioles. There is evidence that cytochrome a3 occurs in wheat-root mitochondria. Cytochromes b, c and c1 of plant mitochondria are reduced enzymically on addition of sodium succinate or reduced diphosphopyridine nucleotide. Cytochrome b appears to be intimately concerned in the succinic dehydrogenase system of plants. The nature of plant succinic dehydrogenase is briefly discussed. A haemprotein, here called cytochrome b3 (M. and M.), is localized almost entirely in the microsome fraction, and is reduced enzymically by addition of reduced diphosphopyridine nucleotide. Spectroscopic observations showed that the supernatant fraction obtained from beet petiole contained in very small amount a labile pigment capable of forming an oxygenated ferrous complex. However, most of the haematin in this fraction occurred as a complex with denatured protein.