[The effect of the antiauxin p-Chlorophenoxyisobutyric acid on the formation of meristematic centres during regeneration of isolated tissue fragments of Riella helicophylla (Bory et Mont.) Mont].

In isolated tissue fragments of Riella cultured in continuous light, p-Chlorophenoxyisobutyric acid (PCIB) strongly accelerates the polar cell divisions without changing the time of onset of the first nuclear divisions and totally inhibits the formation of unicellular rhizoids. No lateral meristems develop in the cauloids as they do in the control; instead the cells have uniform minimal size. Only preincubating the whole plant in PCIB before the fragments are cut results in a depolarisation with a much higher cell division activity. Preincubation of the whole plant followed by further incubation of the tissue fragments in PCIB decreases the area in which cell embryonization takes place, but the number of cell divisions therein increases to a still larger extent.