Genetic Variation of Ecophysiological Responses to CO2 in Picea glauca Seedlings

ABSTRACT

To investigate genetic variation in the response of white spruce (Picea glauca (Moench) Voss) to CO2 elevations, one-year-old seedlings of 11 provenances from Ontario were grown at 360, 530 and 700 μmol mol-1 CO2 concentrations. After 60 days of treatment, CO2 assimilation rate (A) at growth [CO2] was 32% and 74% higher in the 530 and 700 μmol mol-1 CO2 treatment, respectively, than in 360 μmol mol-1 [CO2]. After 90 days, A under 530 and 700 μmol mol-1 [CO2] was 141% and 223% greater, respectively, than under 360 μmol mol-1 [CO2]. When measured at a common [CO2] (360 μmol mol-1), however, A under 530 and 700 μmol mol-1 [CO2] treatment was 39% and 53% lower than in the 360 μmol mol-1 [CO2] treatment, respectively, after 60 days of treatment, and 22 and 35% less, respectively, after 90 days. The CO2 elevations also significantly suppressed Vcamx, Jmax and TPU after 60 days and 90 days of treatment. The [CO2] elevations significantly reduced Stomatal conductance and transpiration after 60 days of treatment, but not after 90 days. gs was 28% and 35% lower under 530 and 700 μmol mol-1 [CO2], respectively, than under 360 μmol mol-1 [CO2] after 60 days of treatment. E was 23 and 33% lower under 530 and 700 μmol mol-1, respectively, than under 360 μmol mol-1 [CO2]. 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 μmol mol-1 [CO2] than under 360 μmol mol-1 [CO2]. There were no significant between-provenance differences in any of the above responses; nevertheless, the ecophysiological performance of seedlings was closely correlated with the temperature and precipitation regimes of the seed origin. In addition, provenance significantly affected seedling total biomass, shoot mass, shoot/root ratio and height growth.

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