Figure 4.

Proposed model of thylakoid membrane response to PSII-specific illumination. Before illumination, thylakoids are in state 1, and then an intermediate state (0–90 s) occurs as the membrane begins to stiffen (depicted by a change in membrane color) in response to formation of the pH gradient. Next, lumen expansion and swelling occur (90–300 s), driven by LHCII phosphorylation and membrane unstacking, while further membrane stiffening takes place. Finally, migration and association of phosphorylated LHCII with PSI result in establishment of state 2. To see this figure in color, go online.