Date of Award


Document Type


Degree Name

Master of Science




Photosynthetic rates were measured under constant conditions over a 24 hour period for cultures of Skeletonema costatum and Amphidinium carterae grown under various light - dark regimes. Photosynthetic rate fluctuated for both species under all photoperiods except for A. carterase under 8 hours light per day. Maximum photosynthetic rates occurred generally in the middle of the. light period and minimum the middle of the dark period. The ratio of maximum to minimum rates, or Pmax/min, differed significantly under the various photoperiods. Pmax/min values . for A. carterae were significantly greater than for s. costatum. The greatest Pmax/min for S ." cos ta tum occurred under 12 hours light per day and for A. carterae under 14 hours per day. Considering the differences in response of the two species to the same photoperiods, it is possible that species composition could have a.n effect on field data which relates Pmax/min to latitude and season.

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