In natural environments, photosynthetic organisms experience frequent changes in the light supply, requiring modulation of light harvesting and electron transfer reactions to avoid mismatch between light conversion and metabolic reactions that may result in the production of harmful reactive oxygen species. They have thus evolved photoprotective regulatory mechanisms including the dissipation of excess energy (or non-photochemical quenching, NPQ), which relies on specific light-harvesting antennae, such as PSBS and Light-Harvesting Complex Stress-Related 3 (LHCSR3) (Peers et al., 2009), and is triggered by low pH in the thylakoid lumen. The photosynthetic control, which consists of a downregulation of electron flow between photosystems II and I (PSII and PSI) by the slowing effect of transthylakoidal proton gradient on cytochrome b6f electron transfer, also contributes to photoprotection (Suorsa et al., 2012). Cyclic electron flow around PSI (CEF), which involves Proton Gradient Regulation 5 (PGR5) and PGR5-Like Photosynthetic Phenotype 1 (PGRL1), generates a component of the proton gradient critical for the induction of both NPQ (Munekage et al., 2002) and photosynthetic control (Tolleter et al., 2011; Suorsa et al., 2012). In the present study, we questioned whether NPQ strictly depends on CEF, and whether these two mechanisms may work independently. We also explored to what extent these regulatory mechanisms could limit the maximal capacity of CO2 assimilation and biomass productivity by excessively downregulating the photosynthetic electron flow, as it was recently reported that biomass productivity was increased in the Chlamydomonas reinhardtii npq4 mutant (Berteotti et al., 2016).