respiration (Q10) remained unaffected by the drought treatment (overall average SE 2.0 0.1) (Fig. 5b). Tracer concentra- tions in root respired CO2 (Fig. 6) peaked within 8 and 24 h after pulse labelling in control plots and after 24 h in drought plots, where peak values tended to be lower (P = 0.100). The MRT of 13C in root respired CO2 (Table 1) was 93 7h in control plots and 239 83 h in drought plots (n = 3, SE, P = 0.200).