MARKERS OF ADVENTITIOUS ROOT-FORMATION

This article deals with markers for rootability of cuttings and marker s for the successive phases in adventitious root formation. Since root ability depends on the ontogenetic, developmental and physiological st ate of the cuttings, markers for these states may be used as markers f or rootability. For example, morphological characteristics that indica te the adult state, also indicate low rootability. For the phases in a dventitious root formation, physiological parameters are reliable mark ers, in particular transient sensitivity to plant growth regulators ap plied as a pulse. The reliability of biochemical markers, in particula r changes in peroxidase activity, is disputed. Molecular markers may b e obtained from very sensitive screening techniques, from mutant-studi es or from studies that do not deal with adventitious root formation, eg, research on auxin action, cell cycle activation or meristem organi zation. On the molecular level, research has started only recently. Mo lecular markers will require validation by physiological and histologi cal studies.