Practical uses of peroxidase activity as a predictive marker of rooting performance of micropropagated shoots

— A peak of specific peroxidase activity (increase in enzyme activity followed by decrease) has generally been found in crude extracts of stemor shoot-cuttings prior to root formation. Effectors, some of them of a phenolic nature, play a role in these changes in peroxidase activity. This may explain discrepancies in some investigations dealing with partially purified extracts or cell fractions. The peroxidase peak does not terminate the rooting inductive period as proposed some years ago, but rather the initiative phase before identification and growth of endogenous root primordia. Depending upon the materials studied, characteristics of the peroxidase peak such as precocity of appearance, height, and velocity of decrease have been correlated with ulterior rooting performance. Physical and/or chemical factors which were able to modulate the peak also had effects on subsequent rooting rate. An early test us- ing peroxidase activity of extracts made from shoots before transferring to rooting media determined the phenol com- pounds capable of enhancing the rooting process and the moment of application in relation to the peroxidase peak.