Role of the xanthophyll cycle in photoprotection elucidated by measurements of light-induced absorbance changes, fluorescence and photosynthesis in leaves of Hedera canariensis
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The role of the xanthophyll cycle in regulating the energy flow to the PS II reaction centers and therefore in photoprotection was studied by measurements of light-induced absorbance changes, Chl fluorescence, and photosynthetic O2 evolution in sun and shade leaves of Hedera canariensis. The light-induced absorbance change at 510 nm (ΔA510) was used for continuous monitoring of zeaxanthin formation by de-epoxidation of violaxanthin. Non-radiative energy dissipation (NRD) was estimated from non-photochemical fluorescence quenching (NPQ).
High capacity for zeaxanthin formation in sun leaves was accompanied by large NRD in the pigment bed at high PFDs as indicated by a very strong NPQ both when all PS II centers are closed (F'm) and when all centers are open (F'o). Such Fo quenching, although present, was less pronounced in shade leaves which have a much smaller xanthophyll cycle pool.
Dithiothreitol (DTT) provided through the cut petiole completely blocked zeaxanthin formation. DTT had no detectable effect on photosynthetic O2 evolution or the photochemical yield of PS II in the short term but fully inhibited the quenching of Fo and 75% of the quenching of Fm, indicating that NRD in the antenna was largely blocked. This inhibition of quenching was accompanied by an increased closure of the PS II reaction centers.
In the presence of DTT a photoinhibitory treatment at a PFD of 200 μmol m-2 s-1, followed by a 45 min recovery period at a low PFD, caused a 35% decrease in the photon yield of O2 evolution, compared to a decrease of less than 5% in the absence of DTT. The Fv/Fm ratio, measured in darkness showed a much greater decrease in the presence than in the absence of DTT. In the presence of DTT Fo rose by 15–20% whereas no change was detected in control leaves.
The results support the conclusion that the xanthophyll cycle has a central role in regulating the energy flow to the PS II reaction centers and also provide direct evidence that zeaxanthin protects against photoinhibitory injury to the photosynthetic system.
Key wordsEnergy dissipation photoinhibition xanthophyll cycle zeaxanthin
- F, Fm, Fo, Fv
Fluorescence yield at actual degree of PS II center closure, when all centers are closed, when all centers are open, variable fluorescence
non-photochemical fluorescence quenching
non-radiative energy dissipation
photon flux density
primary acceptor PS II
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- Bilger W, Björkman O and Thayer SS (1989) Light-induced spectral absorbance changes in relation to photosynthesis and the epoxidation state of xanthophyll cycle components in cotton leaves. Plant Physiol 91: 542–551Google Scholar
- Bilger W and Schreiber U (1986) Energy-dependent quenching of dark-level chlorophyll fluorescence in intact leaves. Photosynthe Res 10: 303–308Google Scholar
- Björkman O (1987a) High-irradiance stress in higher plants and interaction with other stress factors. In: Biggins J (ed) Progress in Photosynthesis Research, Vol IV, pp 11–18. Dordrecht: Martinus Nijhoff PublishersGoogle Scholar
- Björkman O (1987b) Low-temperature chlorophyll fluorescence in leaves and its relationship to photon yield of photosynthesis in photoinhibition. In: Kyle DJ, Osmond CB and Arntzen CJ (eds) Photoinhibition, pp 123–144. Amsterdam: Elsevier Science PublishersGoogle Scholar
- Demmig B and Björkman O (1987) Comparison of the effect of excessive light on chlorophyll fluorescence (77 K) and photon yield of O2 evolution in leaves of higher plants. Planta 171: 171–184Google Scholar
- Demmig B, Winter K, Krüger A and Czygan F-C (1987) Photoinhibition and zeaxanthin formation in intact leaves. Plant Physiol 84: 218–224Google Scholar
- Demmig B, Winter K, Krüger A and Czygan F-C (1988) Zeaxanthin and the heat dissipation of excess light energy in Nerium oleander exposed to a combination of high light and water stress. Plant Physiol 87: 17–24Google Scholar
- Demmig-Adams B, Winter K, Krüger A and Czygan F-C (1989a) Light response of CO2 assimilation, dissipation of excess excitation energy, and zeaxanthin content of sun and shade leaves. Plant Physiol 90: 881–886Google Scholar
- Demmig-Adams B, Winter K, Krüger A and Czygan F-C (1989b) Zeaxanthin and the induction and relaxation kinetics of the dissipation of excess excitation energy in leaves in 2% O2, 0% CO2. Plant Physiol 90: 887–893Google Scholar
- Demmig-Adams B, Winter K, Krüger A and Czygan F-C (1989c) Zeaxanthin synthesis, energy dissipation, and photoprotection of photosystem II at chilling temperatures. Plant Physiol 90: 894–898Google Scholar
- Demmig-Adams B, Winter K, Winkelmann E, Krüger A and Czygan F-C (1989d) Photosynthetic characteristics and the ratios of chlorophyll, β-carotene, and the components of the xanthophyll cycle upon a sudden increase in growth light regime in several plant species. Botanica Acta 102: 319–325Google Scholar
- Demmig-Adams B, Adams III WW, Heber U, Neimanis S, Winter K, Krüger A, Czygan F-C, Bilger W and Björkman O (1990) Inhibition of zeaxanthin formation and of rapid changes in radiationless energy dissipation by dithiothreitol in spinach leaves and chloroplasts. Plant Physiol 92: 293–301Google Scholar
- Falkowski PG, Kolber Z and Fujita Y (1988) Effect of redox state on the dynamics of photosystem II during steady-state photosynthesis in eucaryotic algae. Biochim Biophys Acta 933: 432–443Google Scholar
- Kobayashi Y, Köster S and Heber U (1982) Light scattering, chlorophyll fluorescence and state of the adenylate system in illuminated spinach leaves. Biochim Biophys Acta 682: 44–54Google Scholar
- Neubauer C and Schreiber U (1989) Photochemical and non-photochemical quenching of chlorophyll fluorescence induced by hydrogen peroxide. Z Naturforsch 44c: 262–270Google Scholar
- Schäfer C and Björkman O (1989) Relationship between efficiency of photosynthetic energy conversion and chlorophyll fluorescence quenching in upland cotton (Gossypium hirsutum L.). Planta 178: 367–376Google Scholar
- Thayer SS and Björkman O (1990) Leaf xanthophyll content and composition in sun and shade determined by HPLC. Photosynthe Res 23: 331–343Google Scholar
- Weis E and Berry JA (1987) Quantum efficiency of Photosystem II in relation to ‘energy’ dependent quenching of chlorophyll fluorescence. Biochim Biophys Acta 894: 198–208Google Scholar
- Yamamoto HY (1979) Biochemistry of the violaxanthin cycle in higher plants. Pure Appl Chem 51: 639–648Google Scholar