(A) WT and (B) 2cysprxAB plants were acclimated to darkness. Fluorescence and NIR absorption changes were recorded with the NIR-KLAS-100. Chlorophyll-a fluorescence from photosystem II (PSII, violet trace) (left ordinate) and redox changes from photosystem I (PSI, blue), plastocyanin (PC, red) and ferredoxin (Fd, green) (right ordinate) were measured during a fast kinetics analysis consisting of 1.5 s illumination with 162 µmol quanta m−2 s−1 followed by darkening. The analysis of the fluorescence and absorption decay showed slower half-life times for WT than for 2cysprxAB plants. The figure shows recordings typical for all analysis with n = 5 measurements. Complemented lines behaved like WT (supplement). (C) Redox state of the 2-CysPrx ex vivo during a light dark transition. WT plants were acclimated to 650 µmol quanta m−2 s−1 for 30 min (t = 0 s) and then darkened. Samples were harvested (t = 5 s-120 s) and blocked with 100 mM N-ethylmaleimide, separated by SDS-PAGE, immunodecorated with anti-2-CysPrx antibody and visualized by luminescence detection. The band intensities on shortly exposed films were quantified by ImageJ. Data are means ± SD of n = 4 experiments. (D) WT and 2cysprxAB plants were grown in normal (N) light for 42 d (upper row) or for 14 d in growth light followed by 21 d in fluctuating light with 80 s L (20 µmol quanta m−2 s−1)/10 s H (800 µmol quanta m−2 s−1) during the 10 hr light phase (lower row). Growth of 2cysprxAB was inhibited relative to WT in normal light, but the relative growth performance was reversed in fluctuating light. Four plants are shown for each growth condition and genotype.