All analyses were conducted with SAS/STAT software version 9.4 (SAS Institute, Cary, NC, USA). Response variables were analysed separately using a general linear mixed model with the effects of site and seed source (seed orchard) and their interaction considered as fixed effects, while block was treated as a random effect. Data were transformed whenever required to satisfy normality of residuals and homoscedasticity. Means were compared using the Tukey test; differences were considered significant at P < 0.05. We compared Ha, ΔS and Topt for Vcmax, Jmax and gm between the two seed sources by non-parametric tests using proc NPAR1WAY. Proc REG and proc NLIN were used to examine the relationship between response variables and climate of plantation sites. The lack of A–Ci curves at 35 and 40 °C from measurements at the Watford and Deville sites in 2015 made it difficult to examine the site effect on Ha and Topt of Vcmax and Jmax. To overcome this problem, we used a repeated-measures analysis of variance (ANOVA) with temperature from 10 to 30 °C as a repeated measure factor.