The temperature at the location of origin of seed sources (climate of origin) in our study had no effect on their thermal acclimation-related traits. This result may be interpreted as a lack of intraspecific genetic variation in the thermal acclimation of photosynthesis, as recently reported for Eucalyptus tereticornis seedlings grown under controlled conditions (Drake et al., 2017). However, the limitations imposed by our experiment do not allow a clear conclusion to be drawn. In fact, the southern seed source experienced only a 1.7 °C warming in mean July temperature at the most southern plantation site of Wendover (Table 1). Consequently, we could formulate two hypotheses. First, despite a difference of 2 °C in mean July temperature of geographical origins between the two white spruce seed sources used in this study, their parents may have experienced historically a similar range of temperatures, which would explain the lack of difference in Topt between them. Thus, it would be interesting to test other seed sources from more meridional origins and warmer local climates, such as from southern Ontario and the USA, to further test the existence of genetic differentiation in thermal acclimation of photosynthesis. Our second hypothesis relates to the warming conditions experienced by seed sources in the southern plantation sites, which are likely insufficient to detect intraspecific variation in the thermal acclimation of photosynthesis that would be related to local genetic adaptation. Thus, using more southern plantation sites or augmented warming conditions in controlled environments would be necessary to test this last hypothesis.