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.