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Phytoplankton photosynethetic characteristics from fluorescence induction assays of individual cells
Author(s) -
Olson Robert J.,
Chekalyuk Alexander M.,
Sosik Heidi M.
Publication year - 1996
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1996.41.6.1253
Subject(s) - fluorescence , phytoplankton , photosystem ii , quantum yield , chlorophyll fluorescence , photosynthesis , biological system , fluorescence microscope , chlorophyll a , biophysics , dcmu , chemistry , biology , physics , optics , botany , ecology , nutrient
Saturating‐flash fluorescence techniques, which can provide information about the physiological state of phytoplankton, at present measure bulk water samples and so provide “averaged” values for all the fluorescent particles present. In analyzing natural samples, however, more detailed information about the distribution of photosynthetic characteristics among different cell types and(or) individual cells is desirable. Therefore we developed two methods for applying a “pump‐during‐probe” technique on a cell‐by‐cell basis. We used either an epifluorescence microscope or a flow cytometer to make time‐resolved measurements of the increase in chlorophyll fluorescence induced by a rectangular excitation pulse of 100‐ µ s duration. We used a biophysical model of fluorescence induction to obtain information about the quantum yield of photochemistry in photosystem 2 (PS2) and the functional absorption cross‐section for PS2. For several species (including the smallest phytoplankton, Prochlorococcus, which are 0.7 µ m in diameter), the maximum quantum yield of photochemistry in PS2 obtained by averaging data from many individual cells agreed well with estimates derived from bulk measurements of DCMU enhancement of Chl fluorescence.