The plant growth retardant tetcyclacis inhibits cell division growth in rice suspension cultures at concentrations above 10(-6) M. Tracer experiments with rice cells revealed that tetcyclacis reduced the incorporation of mevalonic acid into terpenoids after 30 min, the uptake of leucine, uridine and thymidine after 2 h and their incorporation into the corresponding macromolecules after 3-7 h. The changes in membrane permeability concluded to have been caused by an influence on phytosterol biosynthesis are probably also the explanation for alterations of tetcyclacis-treated cells in the content of macro- and microelements.As shown by immunoassay, tetcyclacis did not modify the levels of endogenous gibberellins (Grossmann et al. 1985), cytokinins and indole acetic acid during a growth cycle of 15 d. However, a clear rise in the abscisic acid (ABA) level occurred during the first 5 d of treatment. In untreated cells such a rise coincided only with the aging of the cell culture in the stationary growth phase. Investigations of the cell polypeptide pattern using sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed that the ABA increase following tetcyclacis treatment seems not to be a consequence of advanced cell aging.