Genetic Variation of Ecophysiological Responses to CO2 in Picea glauca Seedlings

To investigate genetic variation in the response of white spruce (Picea glauca (Moench) Voss) to CO 2 elevations, one-year-old seedlings of 11 provenances from Ontario were grown at 360, 530 and 700 mol mol -1 CO 2 concentrations. After 60 days of treatment, CO 2 assimilation rate (A) at growth [CO 2 ] was 32% and 74% higher in the 530 and 700 mol mol -1 CO 2 treatment, respectively, than in 360 mol mol -1 [CO 2 ]. After 90 days, A under 530 and 700 mol mol -1 [CO 2 ] was 141% and 223% greater, respectively, than under 360 mol mol -1 [CO 2 ]. When measured at a common [CO 2 ] (360 mol mol -1 ), however, A under 530 and 700 mol mol -1 [CO 2 ] treatment was 39% and 53% lower than in the 360 mol mol -1 [CO 2 ] treatment, respectively, after 60 days of treatment, and 22 and 35% less, respectively, after 90 days. The CO 2 elevations also significantly suppressed V camx , J max and TPU after 60 days and 90 days of treatment. The [CO 2 ] elevations significantly reduced Stomatal conductance and transpiration after 60 days of treatment, but not after 90 days. g s was 28% and 35% lower under 530 and 700 mol mol -1 [CO 2 ], respectively, than under 360 mol mol -1 [CO 2 ] after 60 days of treatment. E was 23 and 33% lower under 530 and 700 mol mol -1 , respectively, than under 360 mol mol -1 [CO 2 ]. Photosynthetic water use efficiency (WUE) was 80% and 157% higher after 60 days of treatment and 145% and 196% higher after 90 days, respectively, under 530 and 700 mol mol -1 [CO 2 ] than under 360 mol mol -1 [CO 2