Figure 4. Mean (+ 1 SE) weekly growth (panel a), net photosynthesis (panel b), stomatal conductance (panel c), water use efficiency (panel d), chlorophyll content (panel e), Fv/Fm (panel f) and mortality (panel g) of four V. alpina populations cultivated for eight weeks in a growth chamber at: base (b) treatment (16h light/ 8h dark photoperiod and temperature conditions simulating the average summer temperature at the southernmost warmest stand PRA); extreme (e) treatment (the same conditions as in the base treatment with two day-temperature peaks of 22°C at dawn and 30°C during the day, respectively). Significant (p < 0.05) effects of population (P), treatment (T) and their interaction (P × T) resulting from two-way ANOVAs are shown in the upper right part of the panels. Significance of differences between treatments for each population are summarized by asterisks (** =p < 0.01: * = p < 0.05).