Photoinhibition Protection by Carotenoids of the Xanthophyll Cycle

Plants that are acclimated to high light dissipate excess energy through reactions mediated by a particular group of carotenoids (Fig. 16). This dissipation process is induced by accumulation of protons in the thylakoid lumen which is triggered by excess light. Acidification of the lumen induces an enzymatic conversion of the carotenoid violaxanthin into antheraxanthin and zeaxanthin (Gilmore 1997). The

Figure 15. Response of photosynthesis to light intensity. Photosynthesis increases hyperbolically with irradiance, but photon absorption, and thus the generation of excited chlorophylls, increases linearly. The difference (blue area) between the two processes increases with increasing irradiance and represents the excess excitation energy.

Figure 15. Response of photosynthesis to light intensity. Photosynthesis increases hyperbolically with irradiance, but photon absorption, and thus the generation of excited chlorophylls, increases linearly. The difference (blue area) between the two processes increases with increasing irradiance and represents the excess excitation energy.

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