INVESTIGADORES
LUTZ Vivian Alicia
artículos
Título:
Changes in the in vivo absorption and fluorescence excitation spectra with growth irradiance in three species of phytoplankton
Autor/es:
LUTZ, V.A.; SATHYENDRANATH, S.; HEAD, E.J.H.; LI, W.K.W.
Revista:
JOURNAL OF PLANKTON RESEARCH
Editorial:
OXFORD UNIV PRESS
Referencias:
Lugar: Oxford; Año: 2001 vol. 23 p. 555 - 569
ISSN:
0142-7873
Resumen:
The
fluorescence excitation spectrum is sometimes used as a proxy for the action
spectrum of photosynthesis in phytoplankton. The main assumption behind this
approximation is that the shapes of absorption and fluorescence excitation
spectra are similar except for the absorption by photoprotective pigments,
which do not contribute to the fluorescence spectrum. In this study we compare
the shapes of the absorption and fluorescence spectra in three species of
phytoplankton grown at different irradiances: two diatoms (Thalassiosira
weissflogii and Chaetoceros sp.) and a cyanophyte (Synechococcus
sp.). The contribution to absorption by photoprotective pigments was estimated
for each experiment. Results showed that the differences between the shapes of
absorption and fluorescence spectra were similar to the estimated absorption by
photoprotective pigments only in the case of
Thalassiosira weissflogii.
In Synechococcus sp., and
to a lesser degree in Chaetoceros sp., the differences between the two
types of spectra were larger than the absorption by photoprotective pigments.
In the case of Synechococcus sp. the difference between these spectra
was apparently due mainly to the extreme imbalance of chlorophyll-a
distribution between the two photosystems.
Chaetoceros sp. seemed to be an intermediate case: a small part
of the chlorophyll-a of the cell appeared to be exclusively associated
with photosystem I and therefore did not contribute to fluorescence.
Fluorescence and absorption values were normalised to their values at 545 nm,
and the ratio of normalised absorption to normalised fluorescence was computed
for the blue (439 nm) and red (676 nm) peaks in the spectra. The results showed
that these peak ratios can be used to distinguish between the effects of
photoprotective pigments and the arrangement of the photosynthetic apparatus on
differences between fluorecence and absorption spectra.