| Abstract: | Photosynthetic rates measured in protoplasts isolated from the broivn alga Macrocystis pyrifera (L.) Ag. were compared to those for intact tissue. Both 14C incorporation and O2 evolution gave similar rates of light-saturated protoplast photosynthesis (approximately 0.4 mmol-g chl a?1· min?1). Light saturated photosynthetic rates (Pmax) and light harvesting efficiencies (α) of protoplasts were approximately 40% those of intact tissue. In contrast, protoplasts had a greater substrate affinity for photosynthetic HCO3 uptake (lower K0.5) than intact tissue (0.87 and 4.1 mMolar, respectively), presumably because of a reduction in the thickness of the unstirred boundary layer in the absence of the cell wall. Overall, the data suggest that protoplasts isolated from Macrocystis pyrifera are of valur in the study of photosynthesis. However, experiments with intact tissue are necessary as controls to aid interpretation of protoplast data. |
