Parkhill, J. Dalhousie University, jp@raptor.ocean.dal.ca
Cullen, J. Dalhousie University, john.cullen@dal.ca
Maillet, G. L.. Dalhousie University, maillet@phys.ocean.dal.ca

 
INVESTIGATING KINETICS OF VARIABLE FLUORESCENCE AND NON-PHOTOCHEMICAL QUENCHING AS A FUNCTION OF IRRADIANCE USING A NEW MEASUREMENT SYSTEM
 
The quantum yields of photosynthetic processes vary with irradiance. Different patterns have been observed for quantum yields determined from oxygen production, fluorescence yield, and radiolabelled carbon uptake. Comparisons are compromised by methodological limitations. Carbon uptake experiments have pre-determined incubation times and incubations on short time scales (< 10 minutes) are problematic. Oxygen electrodes and active fluorometry investigate a single sample under a given irradiance, so it is not simple to look at several irradiance levels synoptically. We developed a new measurement system (PAMo'Tron) to provide quasi-synoptic fluorescence measurements under 12 different irradiance levels, allowing for resolution of variable fluorescence and non-photochemical quenching on the minute time scale. We report nutrient-dependent (starved and replete; nitrate- and ammonia- grown) responses for a diatom. Comparison between fluorescence-based estimates of electron flow and radiolabelled carbon fixation show differences in saturating light intensity that are consistent with nitrate reduction as a photoprotective electron sink. We discuss fluorescence measurements as a proxy for photosynthetic capability and how they can resolve changes in photosynthesis on short time scales.
 
Day: Thursday, Feb. 4
Time: 11:45 - 12:00pm
Location: Sweeney Center
 
Code: CS62TH1145S