CYTOCHEMICAL-LOCALIZATION OF PHENOL-OXIDIZING ENZYMES IN LIGNIFYING COLEUS-BLUMEI STEMS

The cytochemical localization of the phenol oxidases, laccase and pero xidase, has been studied in pro-lignifying and lignifying Coleus blume i stem sections using 4-methoxy-alpha-naphthol as substrate. The resul ts illustrated that, for short incubation times, both pro-lignifying a nd lignifying Coleus sections showed H2O2-dependent phenol oxidase (pe roxidase-like) activity in epidermal and vascular tissues, while no de tectable H2O2-independent phenol oxidase (laccase-like) activity was f ound in Coleus tissues. For long incubation times, H2O2-independent ph enol-oxidases can also be detected in these tissues, however, this is probably due to the partial capability of intercellular washing fluid Coleus peroxidase to oxidize 4-methoxy-alpha-naphthol in the absence o f exogenously added H2O2. This illustrates not only the importance of the substrate used, but also the importance of the incubation time, in the cytochemical localization of phenol oxidizing enzymes.