Figure 4: Plants are given a spike in CO2, which induces oscillations in electron transport. In the first phase, photosynthesis is unlimited by TPU and PSI becomes more oxidized by the addition of extra CO2, while proton conductivity remains high. The second phase (blue) is the earliest effect of TPU limitation and is primarily described by PSI and Qa quickly become reduced (measured as PSI ox and qL ), along with constriction of proton flow across the thylakoid membrane (gH+ ) and electron flow to PSI (ket ) blue-shaded region). The third phase (green) begins when slower regulations, which depend on proton-motive force (measured as ECSt ), energy dependent quenching (NPQt ) and photoprotection at cytochrome b6f complex, relieve reduction of the electron transport chain. Finally, the electron transport chain enters a new steady-state (red).
Figure 5