ACTA BIOLOGICA CRACOVIENSIA

PHOTOSYNTHESIS, PHOTOCHEMISTRY, AND PHOTOPROTECTION BY CAROTENOIDS
Chlorophylls and carotenoids are light-harvesting pigments and
essential structural components of photosynthetic pigment-protein
complexes. Due to the optically forbidden character of the
lowest excited singlet state (S 1 /2 1 Ag – ) of relevant carotenoids for
one-photon excitation from the electronic ground state (S 0 /1 1 Ag – )
the relative energy position of the carotenoid S 1 state cannot be
readily investigated by conventional spectroscopic techniques.
This state, however, is generally assumed to be involved in excitation
energy transfer to adjacent chlorophyll molecules, based
on its supposed close energetic proximity to the chlorophyll S 1
(Q y ) state.
The carotenoid S 0 - to S 1 -transition is assumed to be two-photon
allowed and consequently spectral peaks in the TPF spectra
(detected by chlorophyll fluorescence) of light-harvesting complexes
are usually ascribed to this transition. We conducted TPF
studies with the plant major light-harvesting complex and chlorophylls
in solution. From direct comparison to TPF spectra of relevant
chlorophylls in solution we infer that there is no effective
energy transfer from the carotenoid 2 1 Ag – state onto chlorophyll
Q y and/or only direct two-photon excitation of chlorophyll excited
states. Consequences of these findings for recent models of
carotenoid-to-chlorophyll energy transfer and non-photochemical
quenching of chlorophyll fluorescence will be discussed.
2.3.
The light and dark paths of the excited state
deactivation of all-trans and 15-cisβ-carotene
in ionic liquids
Krzysztof Pawlak 1 , Andrzej Skrzypczak 2 ,
Janusz Szurkowski 3 , Grazyna E. Bialek-Bylka 1
1Faculty of Technical Physics, Poznan University of Technology,
Nieszawska Str. 13A, 60-965 Poznan, Poland,
grazyna.bialek-bylka@put.poznan.pl
2Faculty of Chemical Technology, Poznan University of
Technology, Maria Sklodowska-Curie Sq. 2, 60-965 Poznan,
Poland, andrzej.skrzypczak@put.poznan.pl
3Institute of Experimental Physics, University of Gdansk,
Wita Stwosza Str. 57, 80-952 Gdansk, Poland, fizjws@ug.edu.pl
β-Carotene in ionic liquids mimics well spectroscopic data of this
pigment in situ. The light and dark paths of excited state deactivation
of all-trans and 15-cisβ-carotene isomers, very important
in photosynthesis, in ionic liquids: [C 8 -C 1 Im][BF 4 ], [C 7 H 15 OCH 2 -
C 8 Im][BF 4 ], [C 8 H 17 OCH 2 -C 1 Im][BF 4 ]were study by fluorescence
and photoacoustic spectroscopy.
Comparison of absorption spectra of designed by us ionic liquids
and literature data has shown that our ionic liquid purification
technique is very efficient. The [BF 4 ] – based imidazolium
ionic liquids are not as transparent as commonly has been
believed and have non-negligible absorption in the UV-VIS region
with the absorption red tail extending far into the visible region.
Inner-filter effect is responsible for distorted fluorescence
emission spectra and nonlinear calibration curves between fluorescence
intensity and fluorophore concentration. According to
our study, in a case of samples like ionic liquids, in order to minimize
inner-filter effect the micro-cell ought to be used. Other
methods for example dilution may cause changes in the nanostructure
of ions and generate artifacts. Also an excitation wavelength
dependent fluorescence effect (different for various ionic
liquids) known as 'red edge effect' is observed. The energetically
different associated species in ionic liquids are responsible for
this 'red tail'. The maxima of the fluorescence emission spectra of
β-carotene in the investigated ionic liquids are at around 530 nm.
Vol. 53, suppl. 1, 2011
17–22 July 2011, Krakow, Poland
Quenching of the fluorescence intensity of ionic liquids by
β-carotene is not linear with path length of the cell and the values
of fluorescence intensities of ionic liquid spectra differ considerably
with their structures.
The dark (thermal) deactivation of both β-carotene isomers in
investigated ionic liquids takes place in the similar way.
Comparison of thermal deactivation of both isomers shows additional
path of deactivation of excited state 1 1Ag + (cis peak).
The excited state deactivation of all-trans and 15-cisβcarotene
isomers are very sensitive to the ionic liquid structure in
a case of light path in contrast to the dark path-almost no sensitive
to the kind of ionic liquid.
Acknowledgement is made to project DS. 62-176/2011.
2.4.
Seasonal changes of violaxanthin cycle
pigments de-epoxidation in wintergreen and
evergreen plants
Olga V. Dymova, Tamara Golovko
Institute of Biology, Kommunisticheskaya st., 28, 167982,
Syktyvkar, Russia, dymovao@ib.komisc.ru, golovko@ib.komisc.ru
Information on the functioning of carotenoid protective mechanism
in various species and ecological groups are important for
understanding plant adaptation processes. We studied the seasonal
changes of the carotenoids (Car) in the underwood of
evergreen conifers (Abies sibirica, Juniperus communis, Picea
obovata), and in the understory evergreen shrub (Vaccinium
vitis-idaea), and wintergreen herbaceous plants (Ajuga reptans,
Pyrola rotundifolia) growing in the middle taiga subzone
of the European North-East. Mature green leaves and two-yearold
needles were used in the experiments. Separations and
quantifications of Car were carried out by reserved-phase highperformance
liquid chromatography (HPLC). The total
carotenoid content varied in range 500-2800 μg/g DW in
dependence on plant species. Car pool was presented mainly by
xanthophylls (up to 90% of the total Car) independently of
species and season. Among the xanthophylls, the part of lutein
was 70-75%, neoxanthin – near 10%, and violaxanthin – up to
15%. Maximum of the violaxanthin cycle pigments de-epoxidation
(DEPS) was revealed in December – March, minimum was
noted in May-September in all plant species. The understory
herbs were characterized by the twice lower values of DEPS as
compared to woody plants in which the DEPS level was up to
60% in the winter and early spring period. We found out that the
Ajuga plant grown in sunny habitats increased in the pool of
VXC pigments up to 60% (Dymova et al., 2010). A strong positive
correlation between thermal dissipation of light energy and
VXC pigment de-epoxidation (DEPS) was shown for the evergreen
conifers (Yatsko et al., 2011). The role of Car protection
in adaptation evergreen and wintergreen life forms of plants to
northern environments will be discussed.
REFERENCES
DYMOVA OV, GRZYB J, GOLOVKO TK, STRZALKA K. 2010. Characterization
of pigment apparatus in winter-green and summer-green leaves
of a shade-tolerant plant Ajuga reptans. Russ. J. Plant Phys. 57:
755-763.
YATSCO YN, DYMOVA OV, GOLOVKO TK. 2011. Violaxanthin cycle pigments
de-epoxidation and thermal dissipation of light energy in
three boreal species of evergreen conifer plants. Russ. J. Plant
Phys. 58: 169-173.
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