Expression of PIP aquaporins (AQPs) in rice roots at 30 min following shoot removal and application of 80 kPa tension (‘vacuum’) to the detached root system. Following shoot removal of one plant, the excised root system of that plant was connected to a vacuum pump and 80 kPa of vacuum was applied. After 30 min of vacuum application, this ‘vacuum’ plant was harvested. At the same time, the shoot of a ‘control’ plant was excised and the root system harvested immediately. The expression of PIP AQP genes was related to that of reference genes (UBQ, EF-2 and GAPDH), and the resulting value of the control was set to 100 %. The expression of PIP genes in root systems which had a vacuum applied for 30 min was expressed as a percentage of this 100 % value. Results are the averages and s.e. (error bar) of four independent experiments. Expression values did not differ significantly between control and vacuum plants for a particular AQP (P < 0·05, one-way ANOVA followed by Tukey analyses).