A Biolchemical and Cytochemical Study of Peroxidase Activity in Roots ofPisum sativum

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Abstract
Peroxidase activity in roots of Pisum sativum has been examined using both guaiacol and 3,3′-diaminobenzidine (DAB) as hydrogen donors. Biochemically, differences were observed between the two donors with respect to the pH optimum (6–9 and 4–0, respectively), and in response to added NaCl (guaiacol-peroxidase was unaffected while the DAB-peroxidase was markedly inhibited). Both reactions showed highest specific activity in a high speed supernatant fraction, and, of nine anionic bands demonstrated by gel electrophoresis with DAB, only six were visible with guaiacol. Histochemically, similar staining patterns were observed with both donors. Cell wall fractions prepared by bead filtration contained 2% and 3.5% of the total peroxidase and acid phosphatase activities respectively. 50% and 27% of these activities were ionically bound, as indicated by salt treatment In addition, washing with salt solutions produced a marked stimulation of peroxidase activity at high salt concentrations: this affect was not observed with the supernatant peroxidase or with cell wall acid phosphatase. Possible functions of cell wall peroxidase are discussed

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