Figure 1. Summary of chloroplast processes involved in NPQ relaxation.
The figure summarizes known components involved in rapid NPQ relaxation and points to five main questions: (i) How is the zeaxanthin epoxidase (ZEP) distributed among the three chloroplast compartments?, (ii) How is light energy converted into thermal energy?, (iii) Which is the molecular identity of the K+ channel in the thylakoid membrane?, (iv) Does KEA3 act in concert with a K+ channel? and (v) How is KEA3 activity regulated? VDE, violaxanthin de-epoxidase; Vx, violaxanthin; Zx, zeaxanthin; PSII, photosystem II; bf, cytochrome b6f complex; PSI, photosystem I; KEA3, K+ efflux antiporter 3.