Evaluation of visible-light wavelengths that reduce or oxidize the plastoquinone pool in green algae with the activated F rise method.

We recently developed a chlorophyll fluorescence method (activated F rise) for estimating if a light wavelength preferably excites PSI or PSII in plants. Here, the method was tested in green microalgae: , , , , , and . The species displayed a plant-like action spectra of F rise, suggesting that PSII/PSI absorption ratio is conserved from higher plants to green algae. F rise was weak in a strain of , , and . Interestingly, another strain exhibited a strong F rise. The result indicates that the same illumination can lead to different redox states of the plastoquinone pool in different algae. Flavodiiron activity enhanced the F rise, presumably by oxidizing the plastoquinone pool during pre-illumination. The activity of plastid terminal oxidase, in turn, diminished the F rise, but to a small degree.