PHOTOSYNTHETIC AND RESPIRATORY TRANSIENTS OF OXYGEN-EXCHANGE IN CARPOPHYLLUM SPECIES (FUCALES, PHAEOPHYCEAE)

Several transients of oxygen exchange were identified in four Carpophyllum species. A short photosynthetic induction transient characteristic of dark-light changes was sensitive to repition of the cycle, length of the dark incubation period, oxygen tension, pH and CO2 supply. Changes in irradiance alter the induction loss" but have no effect on the induction time. Short induction transients also occur upon stepwise increases in irradiance. Longer photosynthetic transients (up to 18 h for "shade" plants) occur following a reduction from saturating to a lower irradiance. Two respiratory transients characteristic of light-dark changes were noted. A slow increase in oxygen consumption in the first 10-30 min of the darkness was sensitive to incubation irradiance and oxygen tension. A second transient of slowly declining uptake lasting up to several hours was fully developed only after a long light incubation (30 min) and dependent on light intensity but not prior net CO2 fixation. The longer transients may represent a source of error in estimates of productivity of photosynthesis using short exposure times unless appropriate pre-treatments are used. © 1979."