The differential effect of N(6)-benzyl-adenine and N (6)-(Δ (2)-isopentenyl)-adenine on in vitro propagation of Paeonia suffruticosa Andr. is correlated with different hormone contents.

N(6)-benzyl-adenine (BA) enhanced phyllogenesis and axillary bud development of Paeonia suffruticosa during in vitro culture allowing good propagation while N(6)-(Δ(2)isopentenyl)adenine (iP) did not. During the first five days of culture, the mitotic activity of BA-treated explants was higher than in the iP-treated ones. High BA levels were detected in the BA-treated explants, and this was correlated with the absence of or the low indole-3-acetic acid (IAA) content. The low iP levels measured in iP-treated explants were correlated with high endogenous IAA content; the new cytokinin / auxin ratio could explain the lack of axillary buds and the development of only one leaf. Abscisic acid (ABA) was detected neither in the controls nor in the cytokinin-treated explants during the first week. However, intensive restoration of ABA accumulation was observed in controls from the third week onwards. Both BA and iP-treated explants accumulated less ABA than the controls but this hormone appeared later in the BA-treated explants than in the iP-treated ones.