Articles
HORMONE CONTENT AND MERISTEMATIC ACTIVITY OF PAEONIA SUFFRUTICOSA ANDR. CV. “MADAME DE VATRY” VITROPLANTS DURING IN VITRO ROOTING.
The root induction medium (RIM) contained indole-3-butyric acid (IBA). No hormone was supplied into the root development medium (RDM). Histological observations showed an important reduction of mitotic index (MI) in terminal buds when vitroplants were transfered to the RIM. Changes in the level of hormones were calculated with HPLC-ELISA technique in order to be associated with rooting capacity and the loss of meristematic activity.
During root induction, exogenous IBA was quickly absorbed by the explants and was transformed into indole-3-acetic acid (IAA) and IAA conjugates.
In parallel, an important increase of abscisic acid (ABA) production by explants was observed.
The omission of exogenous 6-benzyl-aminopurine (BAP) from the RIM and the addition of IBA in high concentrations into it resulted in the inactivity of the terminal buds of shoots.
Also, the endogenous ABA detected could be implicated in this phenomenon.
Although MI raised soon after transfer to the RDM, shoot development was inhibited and ex vitro establishment was disturbed.
A cold treatment at 4°C caused the increase of the MI and allowed a slow development of vitroplants.
The detection of abscisic acid 
-D- glucopyranosyl ester (ABA-GE) and zeatin riboside (ZR) in the explants and the disappearance of ABA from them at the end of the treatment could be involved in this activation.