L-DOPA CONTENT, PEROXIDASE-ACTIVITY, AND RESPONSE TO H2O2 OF VICIA-FABA L AND VICIA-NARBONENSIS L INSITU AND INVITRO

Comparative investigations on Vicia faba L. and V. narbonensis L. demonstrate that externally applied H2O2 oxidizes L-DOPA to DOPAchrome in young calli and protoplasts isolated from precultured leaves of V. faba, but not in those from V. narbonensis. A specific staining method indicates that peroxidases and not polyphenol oxidases mediate the oxidation of L-DOPA in such tissues and cells. The change in peroxidase activity and L-DOPA content, measured during a long-term callus culture, and in mesophyll protoplasts of both species is described. An orange-red colour is only visible if sufficient amounts of active peroxidases and L-DOPA are present. Cells and tissues without L-DOPA, or with inactive peroxidases, show no reaction to H2O2. Wounding and cell division induce peroxidase activity. Using root cross sections it is demonstrated that cell divisions alone activate peroxidases, and that wounding is not an obligatory factor. © 1990 Springer-Verlag.