Simulation of the influence of each major explanatory factor as predicted by the 2nd-round models. Panels a to c are for respiratory responses (CR, MACYT and MAALT, respectively). Panels d to f are for photosynthetic responses (ΦPSII800, NPQ800 and P800, respectively). The black vertical dotted lines indicate the arithmetic DOE mean, and the small black vertical full straight lines the factor value for which the response is maximal or minimal in case of quadratic profile. The grey curved dotted lines are the 95%-confidence intervals of the simulation. β-weights and individual ANOVA p-values [see also Additional file 3] are displayed and highlighted in bold characters while statistically significant (p ≤ 0.05). For quadratic profiles, these parameters are provided for the second- and first-order parameter estimates (symbolized by x
2 and x, respectively).