Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Endogenous circadian rhythmicity of photosynthesis in the marine alga Iridaea flaccida (Rhotophyta) of the Central California Coast
Student Author(s): Harris, James B.
Faculty Advisor(s): Abbott, I. A.
%E Phillips, John
Pages: 23
Location: Final Papers Biology 175H
Date: June 1978
Keywords: biological rhythms in marine and maritime organisms
Abstract: Endogenous circadian rhythms in photosynthesis are described for the first time in the red alga Iridaea flaccida (S. & G.) Silva. These rhythms persist under constant conditions for three days showing a 36% difference between maximum photosynthetic rates at midday and minimum rates at night. Respiration is constant over the circadian cycle. Changes in the inital slopes of photosynthesis - irradiance curves at different circadian times suggest the involvement of the light reactions in this rhythmicity. Photosynthetic rates of I. flaccida are comparable in air and in water when the thallus is fully hydrated. A small amount of desiccation enhances the photsynthetic rates, while continued desiccation results in a marked decrease.