Relationships of thermal acclimation-related traits with climatic conditions along a latitudinal gradient (spatial) and during a growing season (temporal gradient) for two geographically distant white spruce seed sources. MJT, mean July temperature of plantation site during the two growing seasons (1 year before and current year of measurement); MTBM, mean temperature 5 d before measurements; Topt, optimal temperature for net photosynthetic rate; Aopt, photosynthetic rate at Topt; Rd10, basal rate of respiration (T = 10 °C); Q10, rate of change in Rd with a 10 °C increase in temperature. South SS, southern seed source (SO1-1); North SS, northern seed source (SO1-5).