Fig. 6 Time courses of tracer concentrations in root respired CO2 in control (closed circles) and drought (open circles) plots (n = 3, mean SE). The pulse labelling period is indicated by dotted vertical lines. P-value refers to overall treatment effect, asterisks indicate significance levels of difference of means between control and treatment: *, P ≤ 0.05; (*), P ≤ 0.1.