Photosynthetic rates and respiration during acclimation. (a) Photosynthetic rate at the end of the photoperiod measured on attached leaves of plants within growth cabinets. (b) Dark respiration measured at the end of the photoperiod within growth cabinets. Plants of Ws‐4 wild‐type (squares) and gpt2.2 (triangles) lines were grown at low light (LL, 100 μmol m−2 s−1 white light, 8 h light, 20 °C/16 h dark, 18 °C) for 8 weeks. They were then transferred to high light (HL, 400 μmol m−2 s−1 white light, 8 h light, 20 °C/16 h dark, 18 °C; closed symbols) or maintained at LL (open symbols). LL measurements were made at the beginning of the acclimation period for comparison. Points represent the mean of at least three replicates from three separate plants. Error bars represent ±1 SE. Significant differences between samples were determined using a two‐way anova (P < 0.05, see the Results section for details).