RELATIONS BETWEEN AUXIN AND CYTOKININ CONTENTS AND IN-VITRO ROOTING OF TREE PEONY (PEONIA-SUFFRUTICOSA ANDR)

In this work, a combined HPLC-ELISA technique was used to associate in vitro rooting capacity of tree peony microcuttings with contents of c ytokinin and auxin; the cytokinin mainly detected corresponded to the N-6-benzyladenine which had been added to the multiplication medium. R ooting capacity of explants was favoured by a preliminary accumulation of endogenous IAA only when levels of the BA absorbed from the multip lication medium had decreased. Main shoots coming from a 5-weeks subcu lture fulfilled these hormonal conditions and were the best microcutti ngs for rooting (87% rooting). Main shoots coming from shorter cycles or axillary shoots coming from a 5-weeks cycle always contained high b enzyladenine levels and had a low rooting capacity (25-55% rooting). R oot induction was associated with an early peak of indole-3-acetic aci d followed by a 10-fold lower peak of endogenous ribofuranosyl-isopent enyladenine. Only a low and transitory accumulation of isopentenyladen ine occurred during root development, and this could explain the lack of shoot development. Root development was efficient, especially in a medium containing activated charcoal, which led to an almost 3-fold de crease of IAA contents in roots.