Processing of Excitation Energy by Antenna Pigments
Absorption and transduction of light by photosynthetic organisms provides the principal energy source for all living organisms. At the same time, absorption of excess light (light in excess of the capacity of the organism to use the energy to drive photosynthesis) represents a primary site of environmental injury. Recent studies have shown that photosynthetic organisms have the ability to regulate the utilization of absorbed light energy through a group of related processes commonly called non-photochemical quenching. These process dissipate excess absorbed energy as heat. In order to remain competitive, photosynthetic organisms must seek out the delicate balance between efficient light-harvesting under limiting light conditions and regulated dissipation of energy under excess light conditions. Excess light absorption may occur as the result of increased incident intensity or a decrease in the rate of photosynthesis due to other environmental stresses. The underlying reactions of non-photochemical quenching may occur in the antennae, the reaction centers, or both, and are not well understood. Independent of the quenching site, the reactions of non-photochemical quenching must cooperate and compete with those of normal light-harvesting. Here, the proposed mechanisms of non-photochemical quenching and the common energy transfer reactions affecting both light-harvesting and non-photochemical quenching are examined in order to provide a more general framework in which the utilization of light energy can be described.
KeywordsReaction Center Photochemical Quenching Excited State Energy Reaction Center Complex Antenna Pigment
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