Figure 4.

Improvement of photosynthetic efficiency in detached roots via cytokinin signaling. Photosynthetic parameters are shown for 21-d-old detached roots and intact roots treated with 6-benzyladenine (BA) of the wild type (A) and the arr1 arr12 double mutant (B) compared with untreated intact roots. In A, wild-type leaves were used as a reference of the photosynthetically competent organ. Data are means ± se (n > 4). F_v/F_m, Maximum quantum yield of PSII; F_v′/F_m′, maximum quantum yield of PSII under light conditions; qP, coefficient of photochemical quenching; Y_NPQ, quantum yield of regulated energy dissipation; Y_NO, quantum yield of nonregulated energy dissipation. Slow induction kinetics under actinic light (intensity, 420 µmol photons m⁻² s⁻¹) are shown for Y_II, and other data were obtained after actinic light exposure for 15 min. Different letters indicate significant differences (P < 0.05, Tukey-Kramer multiple comparison test).