Journal of Plankton Research, Vol 21, 269-283, Copyright © 1999 by Oxford University Press
S Lippemeier, P Hartig and F Colijn
Pulse-amplitude-modulation (PAM) fluorometry was used to investigate the
effects of varying the silicate concentration on different fluorescence
characteristics of batch and chemostat cultures of the diatom
Thalassiosira weissflogii. The fluorescence signals,
measured both on- and off-line, were used to calculate the actual
(
ORIGINAL ARTICLES
Direct impact of silicate on the photosynthetic performance of the diatom Thalassiosira weissflogii assessed by on- and off-line PAM fluorescence measurements
Research and Technology Centre Westcoast (FTZ-Westkuste), Gafentorn, 25761 Busum, Germany
P) and potential (
P0) photochemical efficiencies of
the reaction centres of photosystem II (PSII). Also the relative electron
transport rate of the reaction centres of PSII (Je)
was calculated. Fluorescence decreased in silicate-limited cells and
increased rapidly after silicate addition. The decrease was caused by
strong non-photochemical quenching (qN) in
silicate-limited cells. Continuous recording (on-line) of the minimum and
maximum fluorescence provided data with high temporal resolution, revealing
that the first recovery of silicate-limited cells occurred 20 min after the
addition of silicate. Based on these observations, we assume a strong
influence of silicate metabolism on the photosynthetic efficiency of the
reaction centres of PSII assessed by PAM fluorescence. This implies that
silicate, as well as other nutrients, has to be considered as a possible
cause for variable photosynthetic efficiency of diatoms.
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