title: Toward an understanding of the mechanism of nonphotochemical quenching in green plants.
abstract: Oxygenic photosynthesis in plants involves highly reactive intermediates and byproducts that can damage the photosynthetic apparatus and other chloroplast constituents. The potential for damage is exacerbated when the amount of absorbed light exceeds the capacity for light energy utilization in photosynthesis, a condition that can lead to decreases in photosynthetic efficiency. A feedback de-excitation mechanism (qE), measured as a component of nonphotochemical quenching of chlorophyll fluorescence, regulates photosynthetic light harvesting in excess light in response to a change in thylakoid lumen pH. qE involves de-excitation of the singlet excited state of chlorophyll in the light-harvesting antenna of photosystem II, thereby minimizing the deleterious effects of high light via thermal dissipation of excess excitation energy. While the physiological importance of qE has been recognized for many years, a description of its physical mechanism remains elusive. We summarize recent biochemical and spectroscopic results that have brought us closer to the goal of a mechanistic understanding of this fundamental photosynthetic regulatory process.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Holt
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Niyogi
mesh_terms: D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins; D002734:Chlorophyll; D002736:Chloroplasts / Q000378:metabolism; D004583:Electrons; D006863:Hydrogen-Ion Concentration; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008954:Models, Biological; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000502:physiology; D010860:Pigments, Biological; D018521:Plant Physiological Phenomena; D010940:Plant Proteins; D011522:Protons; D013053:Spectrophotometry; D020524:Thylakoids / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; C489731:NPQ4 protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; D010940:Plant Proteins; D011522:Protons; D002734:Chlorophyll