Abstract
The activities of carbonic anhydrase (CA) and photosynthesis of Porphyra haitanensis were investigated in order to see its photosynthetic utilization of inorganic carbon source. Both intra- and extra-cellular CA activities existed in the thallus. CA inhibitors, acetazolamide (AZ) and ethoxy- zolamide (EZ), remarkably depressed the photosynthetic oxygen evolution in seawater of pH 8.2 and 10.0, and EZ showed stronger inhibition than AZ. The observed net pho- tosynthetic rate in seawater of pH 8.2 was much higher than that of CO 2 supply theoretically derived from spontaneous dehydration of HCO 3 - . P. haitanensis also showed a rather high pH compensation point (9.9). The results demonstrated that P. haitanensis could utilize bicarbonate as the external inorganic carbon source for photosynthesis. The bicarbonate utilization was closely associated with 3 HCO - dehydration catalyzed by extracellular CA activity. The inorganic carbon composition in seawater could well saturate the photosynthe- sis of P. haitanensis. The low K m value and compensation points for inorganic carbon reflected the existence of CO 2 - concentrating mechanism in this alga.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
