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Plant Physiol. Jun 1987; 84(2): 218–224.
PMCID: PMC1056560

Photoinhibition and Zeaxanthin Formation in Intact Leaves 1,2

A Possible Role of the Xanthophyll Cycle in the Dissipation of Excess Light Energy

Abstract

Comparative studies of chlorophyll a fluorescence, measured with a pulse amplitude modulated fluorometer, and of the pigment composition of leaves, suggest a specific role of zeaxanthin, a carotenoid formed in the xanthophyll cycle, in protecting the photosynthetic apparatus against the adverse effects of excessive light. This conclusion is based on the following findings: (a) exposure of leaves of Populus balsamifera, Hedera helix, and Monstera deliciosa to excess excitation energy (high light, air; weak light, 2% O2, 0% CO2) led to massive formation of zeaxanthin and a decrease in violaxanthin. Over a wide range of conditions, there was a linear relationship between either variable, Fv, or maximum fluorescence, Fm, and the zeaxanthin content of leaves. (b) When exposed to photoinhibitory light levels in air, shade leaves of H. helix had a higher capacity for zeaxanthin formation, at the expense of β-carotene, than shade leaves of M. deliciosa. Changes in fluorescence characteristics suggested that, in H. helix, the predominant response to high light was an increase in the rate of nonradiative energy dissipation, whereas, in M. deliciosa, photoinhibitory damage to photosystem II reaction centers was the prevailing effect. (c) Exposure of a sun leaf of P. balsamifera to increasing photon flux densities in 2% O2 and 0% CO2 resulted initially in increasing levels of zeaxanthin (matched by decreases in violaxanthin) and was accompanied by fluorescence changes indicative of increased nonradiative energy dissipation. Above the light level at which no further increase in zeaxanthin content was observed, fluorescence characteristics indicated photoinhibitory damage. (d) A linear relationship was obtained between the ratio of variable to maximum fluorescence, Fv/Fm, determined with the modulated fluorescence technique at room temperature, and the photon yield of O2 evolution, similar to previous findings (O Björkman, B Demmig 1987 Planta 170: 489-504) on chlorophyll fluorescence characteristics at 77 K and the photon yield of photosynthesis.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Kitajima M, Butler WL. Quenching of chlorophyll fluorescence and primary photochemistry in chloroplasts by dibromothymoquinone. Biochim Biophys Acta. 1975 Jan 31;376(1):105–115. [PubMed]
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  • Siefermann D, Yamamoto HY. Light-induced de-epoxidation of violaxanthin in lettuce chloroplasts. IV. The effects of electron-transport conditions on violaxanthin availability. Biochim Biophys Acta. 1975 Apr 14;387(1):149–158. [PubMed]
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  • Weber A, Czygan FC. Chlorophylle und Carotinoide der Chaetophorineae (Chlorophyceae, Ulotrichales). I. Siphonaxanthin in Microthamnion keutzingianum Naegeli. Arch Mikrobiol. 1972;84(3):243–253. [PubMed]

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