Scheme of photoprotection mechanisms.

Photoprotection occurs via several different mechanisms, often acting in concert with one another: Avoidance, Photorespiration, Dissipation, and Anti-oxidation. Light energy can be physically avoided by cutting down on light absorption. Absorption of light boosts chlorophyll (Chl) to an excited state (¹Chl*). This excitation energy is utilized to create sugars by means of photosynthesis (or fuels the “futile” metabolic pathway of photorespiration). Excitation energy in excess of what can be utilized in metabolism is harmlessly removed by de-excitation of ¹Chl* (dissipation; see Figure 6) and/or de-excitation of reactive forms of oxygen (anti-oxidation; see Figure 7).