Fig. 3. Correlation heatmap for traits measured under ambient
CO2 (left) or elevated CO2 level
(right). The variables A max variation
and yield variation (ratios for elevated over ambient
CO2) are common to both heatmaps. Color codes express
variation of R, with P<0.05 (*), P<0.01 (**) or
P<0.001 (***). Exp. 2, greenhouse.
Principal component analysis (PCA, Fig. 4) opposed the tentative proxy
traits LSSR, LSSR(sink) and LSSR(sink)*SPAD to the CO2effect on A max and grain yield variation in both
CO2 treatments, indicating negative correlation on both
dimensions of the PCA.