Fig. 1

Metabolic states induced by the selected light and carbon dioxide availabilities. In the reference condition HLHC (high light and high carbon), light and carbon are supplied in excess (250 µmol photons m⁻² s⁻¹, 1% CO₂). The cells can be expected to optimize resource utilization for optimal growth. Under HLHC conditions, growth is restricted by cellular limitations, i.e., saturation of metabolic pathways as for example the Calvin–Benson cycle or other molecular constraints (compare text). Limiting light availability and excess carbon dioxide supply (65 µmol photons m⁻² s⁻¹, 1% CO₂, LLHC) will force the cells into an electron source-limited metabolic state. In this case, the available light has to be exploited as efficiently as possible to achieve optimal growth. Growth is determined by the light harvesting capacity and PSII efficiency. If light is provided in excess, but carbon availability is limiting (250 µmol photons m⁻² s⁻¹, ambient CO₂, HLLC), the cells are expected to reduce expenses for photosynthetic source utilization to optimize sink utilization. In both cases, LLHC and HLLC, cells are expected to respond with reduced growth compared to the HLHC reference state