Non-radiative dissipation of absorbed excitation energy within photosynthetic apparatus of higher plants

The review deals with thermal dissipation of absorbed excitation energy within pigment-protein complexes of thylakoid membranes in higher plants. We focus on the de-excitation regulatory processes within photosystem 2 (PS2) that can be monitored as non-photochemical quenching of chlorophyll (Chl) a fluorescence consisting of three components known as energy-dependent quenching (q(E)), state-transition quenching (q(T)), and photoinhibitory quenching (q(I)). We summarize the role of thylakoid lumen pH, xanthophylls, and PS2 proteins in qE mechanism. Further, both the similarity between qE and q(I), and specific features of q(I), are described. The other routes of thermal energy dissipation are also mentioned, that is dissipation within photosystem I and dissipation through the triplet Chl pathway. The significance of the individual deexcitation processes in protection against photo-oxidative damage to the photosynthetic apparatus under excess photon supply is stretched.