The possible involvement of polyphenol-oxidase and the auxin-oxidase system in root formation and development in cuttings of pistacia vera

It is known that adventitious root formation in Pistacia vera cuttings is greatly affected by age, and cuttings from mature trees require exceptionally high concentrations of applied IBA to root. In this context the possible roles of auxin-oxidase (IAA-O) and polyphenol-oxidase (PPO) have been studied in terms of their activities, inhibition, and with regard to their histological locations. There are indications that IAA-O activity increases with maturity of plant material, but is not significantly affected by etiolation. However, IBA application caused an initial decrease in activity soon after application, followed by a dramatic increase prior to root formation. The activity of PPO decreased with maturity, but was stimulated by etiolation, whereas IBA application had no significant effect. Histologically, both enzymes were located relatively near the sites of root initiation, i.e. IAA-O in the cambial area and phloem, and PPO especially in the secondary xylem and also in the pith.