Figure 6.

Comparison of records of the linearized chlorophyll fluorescence yield (ΔFt) and the linearized quantum yield of PSII (ΔФII). To test the applicability of saturating light pulses for the detection of circatidal rhythms in Arabidopsis thaliana, the experimental plants were exposed to continuous illumination. Saturating light pulses with a 10-min repeat period were applied to quantify the linearized quantum yield of PSII (ΔФII). The linearized chlorophyll fluorescence yield (ΔFt, blue line) was aligned with the timecourse of the lunisolar tidal acceleration (green line, upper panel). The linearized quantum yield of PSII (ΔФII) was aligned with the inverted profile of the lunisolar tidal acceleration (pink line, second alignment from top). Both parameters ΔFt and ΔФII exhibited high degrees of synchrony with the lunisolar tidal acceleration. The lower part of the figure depicts the times of Moon rise and set, as well as the times of Sun rise and set. Relative positions of the Moon and the Sun are indicated above and below the horizon. The bottom trace depicts subjective light/dark cycles.