Relations between auxin and cytokinin contents and in vitro rooting of tree Peony (Paeonia suffruticosa Andr.)

Abstract

In this work, a combined HPLC-ELISA technique was used to associate in vitro rooting capacity of tree peony micro-cuttings with contents of cytokinin and auxin; the cytokinin mainly detected corresponded to the N6-benzyladenine which had been added to the multiplication medium. Rooting capacity of explants was favoured by a preliminary accumulation of endogenous IAA only when levels of the BA absorbed from the multiplication medium had decreased. Main shoots coming from a 5-weeks subculture fulfilled these hormonal conditions and were the best microcuttings for rooting (87% rooting). Main shoots coming from shorter cycles or axillary shoots coming from a 5-weeks cycle always contained high benzyladenine levels and had a low rooting capacity (25–55% rooting). Root induction was associated with an early peak of indole-3-acetic acid followed by a 10-fold lower peak of endogenous ribofuranosyl-isopentenyladenine. Only a low and transitory accumulation of isopentenyladenine 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 decrease of IAA contents in roots.