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@ARTICLE{Franco:51979,
author = {Franco, A. C. and Matsubara, S. and Orthen, B.},
title = {{P}hotoinhibition, carotenoid composition and the
co-regulation of photochemical and non-photochemical
quenching in neotropical savanna trees},
journal = {Tree physiology},
volume = {27},
issn = {0829-318X},
address = {Victoria, BC},
publisher = {Heron},
reportid = {PreJuSER-51979},
pages = {717 - 725},
year = {2007},
note = {Record converted from VDB: 12.11.2012},
abstract = {Plants in the neotropical savannas of central Brazil are
exposed to high irradiances, high air temperatures and low
relative humidities. These conditions impose a selection
pressure on plants for strong stomatal regulation of
transpiration to maintain water balance. Diurnal adjustments
of non-photochemical energy dissipation in photosystem 11
(PSII) provide a dynamic mechanism to reduce the risk of
photoinhibitory damage during the middle of the day when
irradiances and leaf temperatures are high and partial
closure of the stomata results in considerable reductions in
internal CO2 concentration. At the end of the dry season, we
measured diurnal changes in gas exchange, chlorophyll
fluorescence parameters and carotenoid composition in two
savanna tree species differing in photosynthetic capacity
and in the duration and extent of the midday depression of
photosynthesis. Non-photochemical quenching and its quantum
yield were tightly correlated with zeaxanthin concentrations
on a total chlorophyll basis, indicating that the reversible
de-epoxidation of violaxanthin to antheraxanthin and
zeaxanthin within the xanthophyll cycle plays a key role in
the regulation of thermal energy dissipation. In both cases,
a single linear relationship fitted both species. Although
efficient regulation of photochemical and non-photochemical
quenching and adjustments in the partitioning of electron
flow between assimilative and non-assimilative processes
were operating, these trees could not fully cope with the
rapid increase in irradiance after sunrise, suggesting high
vulnerability to photoinhibitory damage in the morning.
However, both species were able to recover quickly. The
effects of photoinhibitory quenching were largely reversed
by midday, and zeaxanthin rapidly converted back to
violaxanthin as irradiance decreased in late afternoon,
resulting in the maximal quantum yield of PSII of around 0.8
just before sunrise.},
keywords = {J (WoSType)},
cin = {ICG-3},
ddc = {630},
cid = {I:(DE-Juel1)ICG-3-20090406},
pnm = {Terrestrische Umwelt},
pid = {G:(DE-Juel1)FUEK407},
shelfmark = {Forestry},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000246531300008},
url = {https://juser.fz-juelich.de/record/51979},
}