The influence of paclobutrazol in the rooting medium on the quality of chrysanthemum vitroplants

Abstract

The quality of vitroplants depends on the factors influencing the last stage before weaning. Vitroplants should be able to survive the transfer to ex vitro conditions and start growing as early as possible. The maturity of the coating and transmission tissues and the functionality of roots and photosystems are among the most important traits. Different measures have been advised to increase the ability for adaptation to ex vitro life, including adding paclobutrazol (PBZ) to the rooting medium. In this paper, we report on the reaction of the chrysanthemum cv. 'Ludo' to the presence of this growth regulator at concentrations of 0.5, 1.0 and 3.0 mg 1 -1 in the rooting medium. The post-weaning analysis revealed that paclobutrazol caused an increase in the whole microshoot and root fresh mass and the chlorophyll content. The length of shoots decreased only on the medium containing 3.0 mg 1 -1 of PBZ. After one month in the greenhouse, shoots that had been rooted on the media containing paclobutrazol grew taller and developed flowers earlier than the control vitroplants. The paclobutrazol-treated microshoots produced less proline than the controls at deflasking and a week later. The parameters characterizing chlorophyll fluorescence were not strongly affected, although Fv/Fm and Fv/Fo were lower in the control vitroplants at deflasking and to a lesser extent after one month in the greenhouse, indicating better adaptation to heterotrophic life.