Markers of adventitious root formation

This article deals with markers for rootability of cuttings and markers for the successive phases in adventitious root formation. Since rootability depends on the ontogenetic, developmental and physiological state of the cuttings, markers for these states may be used as markers for rootability. For example, morphological characteristics that indicate the adult state, also indicate low rootability. For the phases in adventitious root formation, physiological parameters are reliable markers, in particular transient sensitivity to plant growth regulators applied as a pulse. The reliability of biochemical markers, in particular changes in peroxidase activity, is disputed. Molecular markers may be obtained from very sensitive screening techniques, from mutant-studies or from studies that do not deal with adventitious root formation, eg, research on auxin action, cell cycle activation or meristem organization. On the molecular level, research has started only recently. Molecular markers will require validation by physiological and histological studies.