Courtney Van Tassell- Photobiology Lab

Cornell University, Ithaca, NY



Fluorescence was used to measure photoinhibition via photosynthetic efficiency in two organisms, Thalassiosira pseudonana (15 ° C) and Phaeocystis antarctica (0 ° C), using a Pulse Amplitude Modulation Fluorometer (PAM). Observed fluorescence values for photoinhibition were then compared to those predicted from a biological weighting function (BWF radioactive labeling) to determine whether fluorescence was an accurate predictor of actual photosynthetic response. A second objective was to determine if temperature was a major controlling variable in inhibition. Three treatments were given to each organism, including PAR, PAR down to 320 nm, and PAR down to 305 nm, and their responses measured. Results showed that while fluorescence-derived photoinhibition measurements did not strongly correlate with those found from the BWF, fluorescence is still useful in making quick and easy estimates of photosynthetic efficiency. It was also found that temperature is not a strong factor in determining an organism's response, as many other variables are likely involved.

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