Photosynthetic electron transport transients in Chlorella vulgaris under fluctuating light
2019
Bonnanfant, Marlene | Jesus, Bruno | Pruvost, Jeremy | Mouget, Jean-Luc | Campbell, Douglas A.
Chlorella sp. is both an important model for green algal photosynthesis and is produced using industrial scale photobioreactors. In photobioreactors, cells travel through steep gradients of illumination at rates determined by photobioreactor design, mixing rates, culture density and surface irradiance levels. We used non-invasive, rapid fluorescence measures to show that Chlorella vulgaris tolerates short-term exposures to super-saturating irradiance by transiently accelerating electron transport away from Photosystem II. This capacity lasts for only 10–20s, and longer exposures to supersaturating irradiance induced down-regulation of electron transport through slowing of down-stream electron sinks, induction of non-photochemical quenching and net Photosystem II photoinactivation. Cells previously acclimated to high growth light were able to partially recover from the down regulation within 300–600s, but cells previously acclimated to low growth light suffered more sustained down-regulation after exposure to super-saturating light. These metrics can be used to guide and constrain culture density, mixing rate and irradiance regime decisions in photobioreactors.
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