Fig. 4: A dark anoxic incubation reestablish the initial fast electron flux.

Following an hour of dark incubation in the presence of O₂ scavengers (GOx), C. reinhardtii wild-type strain CC124 cells were subjected to a series of fixed duration of light exposures (370 µE m⁻² s⁻¹ for 2 min, white background) hatched with an increasing duration of anoxic dark incubations 0–15 min. a H₂ accumulation as a function of the preceded dark incubation time (gray background) between fixed 2 min of irradiance. The production of H₂ in each light exposure was measured by MIMS and the trace is highlighted according to its preceding duration of dark incubation (initial exposure, 0—dashed, 3 min—purple, 5 min—blue, 7 min—green, 10 min—yellow, 15 min—red, additional 3 min—dotted pink, the same color index was used for all the traces in all panels). b To assist the comparison between the differences in H₂ accumulation traces shown in panel a, all the traces measured at each light period are plotted at once using a single fixed time frame. c To assess the changes in the PSII photosynthetic efficiency, Chl a fluorescence was simultaneously measured. During each illumination, the cells were exposed to a saturating pulse and maximal fluorescence (Fm’) was determined. Photosynthetic efficiency was then normalized to Fm’. d Thermoluminescence of intact algal cells was measured after 2 single turnover flashes (STF) spaced 1 s apart. Samples were measured following an hour of dark anaerobic incubation (gray). Then, they were illuminated for 2 min followed by a dark relaxation of either 5 (blue) or 15 (red) minutes, and the temperature in which the maximal values for the B-band were detected. The gained values were plotted in box plots. Each experiment was repeated using at least three biological replicates.