Partial auxin deprivation affects endogenous cytokinins in an auxin-dependent,cytokinin-independent tobacco cell strain

The dynamics of individual endogenous cytokinins within the growth cycle (subculture interval) of an auxin-dependent and cytokinin-independent cell suspension culture ofNicotiana tabacum L. (strain VBI-0) were determined using high performance liquid chromatography and radioimmunoassay. In cells grown at an optimum auxin concentration the transient maxima of N⁶-(²-isopentenyl)adenine and N⁶-(²-isopentenyl)-adenosine correlated with the onset of cell division. Cultivation of the cells in a partially auxin-deprived medium resulted in ca. tenfold increase of all endogenous cytokinins. A very distinct maximum of N⁶-(²-sopentenyl) adenine appeared at the beginning of subculture. This indicates that a lack of auxin induced an accumulation of cytokinins predominantly in the form of the free bases, which are physiologically more active than the corresponding ribosides.Abbreviations iP N⁶-(²-isopentenyl)adenine - 9R]iP N⁶-(²-isopentenyl)adenosine - t-Z trans-zeatin - t-9R]Z trans-zeatin riboside - IAA indole-3-acetic acid - NAA 1-naphthaleneacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - f.w. fresh weight - SBI subculture interval - C complete medium - PAD partially auxin-deprived medium - RP-HPLC reverse phase high performance liquid chromatography - RIA radioimmunoassay - PAL L-phenylalanine ammonia lyase