1997 Articles

Pump-During-Probe Fluorometry of Phytoplankton: Group-Specific Photosynthetic Characteristics from Individual Cell Analysis

Chekalyuk, Alexander M.; Olson, Robert J.; Sosik, H. M.

Saturating-flash fluorescence techniques are used to monitor the state of the photosynthetic apparatus in phytoplankton under natural conditions. At present these are bulk water measurements, which produce estimates of average properties of all the fluorescent particles present in a sample. Here we describe an improved approach for single-cell measurements of phytoplankton. We have combined individual- cell 'pump-during-probe' measurements of chlorophyll fluorescence induction on the time scale of 30 to 100 microseconds with flow cytometric characterization of each cell, to obtain population-specific photosynthetic characteristics. The results provide information about the potential quantum yield of photochemistry, the fraction of functional reaction centers, and the functional absorption cross section for photosystem 2.