INHIBITION OF FLOWER INDUCTION ON IN-VITRO CHICORY ROOT EXPLANTS BY HYDROPONIC FORCING PRETREATMENT OF ROOTS

Fragments of vernalized chicory roots (Cichorium intybus L.) cultured in vitro under continuous light flower almost 100%. When chicory roots were placed in hydroponic forcing before in vitro culture, flowering percentage was reduced by half. The build-up of inhibition during 3 we eks of hydroponic forcing was studied in detail. The third week, in wh ich growth of the chicory head is the strongest, was especially import ant in the inhibition process. When the root apex was eliminated durin g hydroponic forcing, flowering inhibition in vitro was weaker. The sa me observation was made when adventitious roots, developed during hydr oponic forcing, were removed. The photoperiodic conditions during hydr oponic forcing had no influence on the build-up of inhibition. It is s uggested that activity of the apex and, possibly, of the adventitious roots during hydroponic forcing cause the flowering inhibition on chic ory root fragments in vitro.