In the present study, the temperature response of An was Rubisco-limited (Vcmax) over the entire range of needle temperature (10–40 °C), which follows the common trend observed for cold-adapted species (Kattge and Knorr, 2007; Sage and Kubien, 2007; Sage et al., 2008; Yamori et al., 2010). This result suggests that the observed lack of thermal acclimation potential of white spruce may result from (1) lack of nitrogen reallocation from Aj to Ac and (2) Rubisco activase (RCA) lability. The similar Jmax25:Vcmax25 ratio between the southern and northern plantation sites is in accordance with our previous results during the second growing season at the same sites for six seed sources, including those used here (Benomar et al., 2016), and with other reports (Sage et al., 2008; Dillaway and Kruger, 2010). This lack of adjustment of nitrogen invested in Rubisco (and other soluble proteins involved in the Calvin cycle) may be due to cold adaptation-related constraints on nitrogen allocation. In fact, it has been reported that cold-adapted species allocate more nitrogen to Jmax as a compensatory response to low temperature (Yamori et al., 2010). Vcmax depends not only on Rubisco concentration but also on its activation state (inhibited/activated) (Salvucci and Crafts-Brandner, 2004; Sage et al., 2008). The activation state of Rubisco is regulated by RCA, a heat-labile enzyme using energy via ATP hydrolysis to release inhibitors from the active site of Rubisco (Crafts-Brandner and Salvucci, 2000; Yamori and von Caemmerer, 2009). A decrease in RCA activity has been documented as a primary cause of reduced Rubisco activity and then photosynthetic performance in response to increasing growth temperature (Yamori and von Caemmerer, 2009). Investigations regarding genetic variation in RCA and its activity in response to temperature in white spruce would help refine our understanding of the observed biochemical photosynthetic responses to temperature.