Hormonal control of adventitious rooting: Progress and questions

According to the traditional concept, adventitious rooting is a single developmental process, controlled by one single chief actor, auxin. This concept is out-of-date. This review develops the arguments for rooting as a process consisting of successive physiological phases, with different exogenous requirements. The levels of auxins, peroxidases, phenolic compounds, cytokinins, polyamines, and ethylene undergo typical changes during these phases. Their complex interactions are far from being elucidated. The changes characterizing the rooting inductive phase may be similar to those occurring during flowering evocation. Thus these changes seem to be more indicative of a shift in a developmental programme than of a specific organogenic process.