Fig. 1.

Non-sequential rapid light response treatment and measuring protocol. On the Y axis we plot the sequence of light levels applied for 30 s each. Arrowheads show applications of repeated Fast Repetition and Relaxation chlorophyll fluorescence (FRRf) measurements, as demonstrated in annotated inset graphs. The initial FRRf measurement (inset a) was performed following dark adaptation of samples, with all subsequent measurements (inset b) performed following 30 s at respective light levels. For each measurement, a fast fluorescence induction and relaxation measurement were applied both in the presence of background actinic light (insets), and following 1 s darkness (not shown) immediately after exposure to the preceding light step, to allow reopening of photosystem II