FIGURE 1.

High light induces severe PSI acceptor limitation in fd2 plants. Photosynthetic electron transport and CO₂ fixation in wild type (black bars) and fd2 mutant (white bars) plants incubated at either 150 μmol quanta m⁻² s⁻¹ in growth light (HL−) or 600 μmol quanta m⁻² s⁻¹ in high light (HL+) for 2 h, then dark adapted for 15 min before measuring. A, chlorophyll fluorescence parameters for PSII capacity (ΦII), photochemical quenching (qP), non-photochemical quenching (NPQ), and electron transfer rate (ETR). B, maximum P700-oxidation in far red light (ΔA_P700-max); *, no detectable activity. C, steady state CO₂ assimilation rates were measured at least 2 h into the light period. Values are mean ± S.D. of at least 3 independent measurements.