The robustness of a leaf elongation bioassay was evaluated by conducting trials with detached shoots of wheat at several different temperatures. Leaf elongation rate (LER) was monitored for shoots fed either an artificial xylem solution or xylem solution plus 10−3mol m−3 abscisic acid (ABA). Consistent results were obtained when periodic ruler measurements of many shoots were made and compared with simultaneous measurements on a single shoot made with a linearly variable displacement transducer (LVDT). ABA treatment consistently inhibited leaf growth; however, the magnitude of the inhibition was dependent on the temperature at which the assay was conducted. Interpretation of results from such bioas-says in terms of ABA concentration supplied to the detached shoots is complicated by this observation since there is no unique relationship between leaf growth inhibition and ABA concentration. The results are discussed in terms of chemical signalling affecting the growth rate of plants in drying soil.