Stereochemical requirements of the saturable uptake carrier for abscisic acid in carrot suspension culture cells

The saturable uptake carrier in Daucus carota (carrot) suspension culture cells was used as a test system to measure the ability of the separate enantiomers of a range of analogues to inhibit the uptake of (+)-[ 14 C]abscisic acid (ABA). A quantitative measure of the ability of the analogues to compete with [ 14 C]ABA (0.41 μM) for the component of absorption mediated by a saturable uptake carrier was determined. The K i of each analogue was calculated by linear regression of a Dixon plot of 1/(saturable component of uptake of (+)-[ 14 C]ABA) against the concentrations of the added analogue