Abstract
In dark-adapted spinach leaves approximately one third of the Photosystem II (PS II) reaction centers are impaired in their ability to transfer electrons to Photosystem I. Although these ‘inactive’ PS II centers are capable of reducing the primary quinone acceptor, QA, oxidation of QA − occurs approximately 1000 times more slowly than at ‘active’ centers. Previous studies based on dark-adapted leaves show that minimal energy transfer occurs from inactive centers to active centers, indicating that the quantum yield of photosynthesis could be significantly impaired by the presence of inactive centers. The objective of the work described here was to determine the performance of inactive PS II centers in light-adapted leaves. Measurements of PS II activity within leaves did not indicate any increase in the concentration of active PS II centers during light treatments between 10 s and 5 min, showing that inactive centers are not converted to active centers during light treatment. Light-induced modification of inactive PS II centers did occur, however, such that 75% of these centers were unable to sustain stable charge separation. In addition, the maximum yield of chlorophyll fluorescence associated with inactive PS II centers decreased substantially, despite the lack of any overall quenching of the maximum fluorescence yield. The effect of light treatment on inactive centers was reversed in the dark within 10–20 mins. These results indicate that illumination changes inactive PS II centers into a form that quenches fluorescence, but does not allow stable charge separation across the photosynthetic membrane. One possibility is that inactive centers are converted into centers that quench fluorescence by formation of a radical, such as reduced pheophytin or oxidized P680. Alternatively, it is possible that inactive PS II centers are modified such that absorbed excitation energy is dissipated thermally, through electron cycling at the reaction center.
Similar content being viewed by others
Abbreviations
- ΔA518:
-
absorbance change at 518 nm, reflecting the formation of an electric field across the thylakoid membrane
- ΔAFL1 :
-
amplitude of the fast (<100 ms) phase of ΔA518 induced by the first of two saturating, single-turnover flashes spaced 30 ms apart
- ΔAFL2 :
-
amplitude of the fast (<100 ms) phase of ΔA518 induced by the second of two saturating, single-turnover flashes spaced 50 ms apart
- DCBQ:
-
2,6-dichloro-p-benzoquinone
- Fo:
-
yield of chlorophyll fluorescence when QA is fully oxidized
- Fm:
-
yield of chlorophyll fluorescence when QA is fully reduced
- Fx:
-
yield of chlorophyll fluorescence when QA is fully reduced at inactive PS II centers, but fully oxidized at active PS II centers
- Pheo:
-
pheophytin
- P680:
-
the primary donor of Photosystem II
- PPFD:
-
photosynthetic photon flux density
- QA :
-
Primary quinone acceptor of PS II
- QB :
-
secondary quinone acceptor of PS II
References
Chylla RA (1990) Observation and characterization of inactive Photosystem II reaction centers. PhD Thesis. University of Illinois, Urbana, IL
Chylla RA and Whitmarsh J (1989) Inactive Photosystem II complexes in leaves: Turnover rate and quantitation. Plant Physiol 90: 765–772
Chylla RA and Whitmarsh J (1990a) Light saturation response of inactive Photosystem II reaction centers in spinach. Photosynth Res 25: 39–48
Chylla RA and Whitmarsh J (1990b) Measurement of the complete oxidation kinetics of QA - in spinach leaves using flash fluorescence. In: Baltscheffsky M (ed) Current Research in Photosynthesis, Vol 1, pp 383–386. Kluwer Academic Publishers, Dordrecht, The Netherlands
Chylla RA, Garab G and Whitmarsh J (1987) Evidence for slow turnover in a fraction of Photosystem II complexes in thylakoid membranes. Biochim Biophys Acta 894: 562–571
Demmig-Adams B (1990) Carotenoids and photoprotection in plants: A role for the xanthophyll zeaxanthin. Biochim Biophys Acta 1020: 1–24
Graan T and Ort DR (1986) Detection of oxygen-evolving Photosystem II centers inactive in plastoquinone reduction. Biochim Biophys Acta 852: 320–330
Henrysson T and Sundby C (1990) Characterization of Photosystem II in stroma thylakoid membranes. Photosynth Res 25: 107–117
Krause GH and Weis E (1991) Chlorophyll fluorescence and photosynthesis: The basics. Annu Rev Plant Physiol Plant Mol Biol 42: 313–349
Lavergne J and Leci E (1993) Properties of inactive Photosystem II centers. Photosynth Res 35: 323–343
Lavergne J and Trissl HW (1995) Theory of fluorescence induction in Photosystem II: Derivation of analytical expressions in a model including exciton-radical-pair equilibrium and restricted energy transfer between photosynthetic units. Biophys J 68: 2474–2492
Lee WJ and Whitmarsh J (1989) The photosynthetic apparatus of pea thylakoid membranes: Response to growth light intensity. Plant Physiol 89: 832–840
Melis A (1985) Functional properties of Photosystem IIβ in spinach chloroplasts. Biochim Biophys Acta 808: 334–342
Neale PJ and Melis A (1990) Activation of a reserve pool of Photosystem II in Chlamydomonas reinhardtii counteracts photoinhibition. Plant Physiol 92: 1196–1204
Nedbal L and Whitmarsh J (1992) Photosystem 2 reaction centers inactive in plastoquinone pool reduction: A brief overview. Photosynthetica 27: 57–61
Nedbal L, Gibas C and Whitmarsh J (1991) Light saturation curves show competence of the water splitting complex in inactive Photosystem II reaction centers. Photosynth Res 30: 85–94
Robinson SP and Portis AR (1988) Involvement of stromal ATP in the light activation of ribulose 1,5-bisphosphate carboxylase/oxygenase in intact isolated chloroplasts. Plant Physiol 86: 293–298
Snel JFH, Boumans H and Vredenberg WJ (1992) Formation of inactive PS2 centers in spinach leaves during light adaptation. In: Murata N (ed) Research in Photosynthesis, pp 615–618. Kluwer Academic Publishers, Dordrecht, The Netherlands
van Wijk KJ, Andersson B and Styring S (1992) Spectroscopic characterization of photoinhibited Photosystem II and kinetic resolution of the triggering of the D1 reaction center protein for degradation. Biochim Biophys Acta 1100: 207–215
van Wijk KJ, Schnettger B, Graf M and Krause GH (1993) Photoinhibition and recovery in relation to heterogeneity of Photosystem II. Biochim Biophys Acta 1142: 59–68
Witt HT (1979) Energy conversion in the functional membrane of photosynthesis. Analysis by light pulse and electric pulse methods. The central role of the electric field. Biochim Biophys Acta 505: 355–427
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Oxborough, K., Nedbal, L., Chylla, R.A. et al. Light-dependent modification of Photosystem II in spinach leaves. Photosynth Res 48, 247–254 (1996). https://doi.org/10.1007/BF00041015
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00041015