The effect of IBA on anatomical changes and antioxidant enzyme activity during the in vitro rooting of smoke tree (Cotinus coggygria Scop.)

• Root formation is accompanied by an increase in IAA oxidase and the H2O2 level.
• The reduction in POX activity and polyphenolic acid content occurred during root formation.

Induction of adventitious roots is crucial for the in vitro micropropagation of woody species. In this study the histological and biochemical aspects of the adventitious root formation in microcuttings of smoke tree were evaluated. Smoke tree shoots grown on Murashige and Skoog's (1962) medium with 1 mg dm−3 N6-benzyladenine (BA) and 0.1 mg dm−3 1-naphtaleneacetic acid (NAA) were transferred onto a rooting medium with or without 20 mg dm−3 indole-3-butyric acid (IBA) and sampled at various intervals for histological and biochemical analyses of the rooting process. First cell divisions were observed on the first day of culture in the area of primary bark identifiable root primordia with an oval shape and several cell layers were present at Day 3 in cuttings on both media. Roots with organized tissue were observed 9 days after the root induction on the medium with IBA; In shoots rooted on medium with IBA, the induction phase corresponded to a transient increase in the oxidase indole-3-acetic acid (IAAO) activity and levels of endogenous indole-3-acetic acid (IAA) and hydrogen peroxide (H2O2) coincidental with a reduction in the peroxidase (POX) and polyphenol oxidase (PPO) activity and the polyphenoloacids contents. An increase the PPO and POX activity, accompanied by a low activity of IAAO during phases of root development and elongation resulted in a reduction of the endogenous auxin and H2O2 contents in the IBA-treated cuttings.