Fig. 2. Mean WVA uptake fluxes (± s.e.m.; vertical error bars), expressed both as the exothermic heat signal (HF_WVA; µW) and the uptake flux (µg h^–1), plotted as a function of the steady-state relative humidity in the calorimetric cell (RH_s–s in %). RH_s–s values are calculated as indicated in the text and the data points represent the means for each RH-step (± s.e.m.; horizontal error bars). Water vapour uptake in P. lagurus increases linearly with relative humidity up to 92% RH, but shows asymptotic kinetics above this value. N=4-16.