Evaluation of visible-light wavelengths that reduce or oxidize the plastoquinone pool in green algae with the activated F0 rise method

Abstract

<p> We recently developed a chlorophyll <em>a</em> fluorescence method (activated F₀ rise) for estimating if a light wavelength preferably excites PSI or PSII in plants. Here, the method was tested in green microalgae: <em>Scenedesmus quadricauda</em>, <em>Scenedesmus ecornis</em>, <em>Scenedesmus fuscus</em>, <em>Chlamydomonas reinhardtii</em>, <em>Chlorella</em> <em>sorokiniana</em>, and <em>Ettlia oleoabundans</em>. The <em>Scenedesmus</em> species displayed a plant-like action spectra of F₀ rise, suggesting that PSII/PSI absorption ratio is conserved from higher plants to green algae. F₀ rise was weak in a strain of <em>C. reinhardtii</em>, <em>C. sorokiniana</em>, and <em>E. oleoabundans</em>. Interestingly, another<em> C. reinhardtii</em> strain exhibited a strong F₀ 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 F₀ rise, presumably by oxidizing the plastoquinone pool during pre-illumination. The activity of plastid terminal oxidase, in turn, diminished the F₀ rise, but to a small degree <br></p>