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Received April 10, 2008; Revision received May 7, 2008
Competitive and complimentary relationships of various peroxidase substrates were studied to elucidate the enzymatic mechanisms underlying production of reactive oxygen species in plant cell apoplast. Dianisidine peroxidase released from wheat seedling roots was inhibited by ferulate and coniferol, while ferulic and coniferyl peroxidases were activated by o-dianisidine. Both ferulate and coniferol, when added together with hydrogen peroxide, stimulated superoxide production by extracellular peroxidase. We suggest that substrate–substrate activation of extracellular peroxidases is important for stress-induced oxidative burst in plant cells.
KEY WORDS: wheat root, superoxide, peroxidase, phenol, extracellular solution