Chromatic Transients in Photosynthesis of RedAlgae 



L. R. BLINKS, Hopkins Marine Station of Stanford University, Pacific Grove, 



California 



Induction lags, oxygen "spikes," carbon dioxide gushes, and other 

 transient phenomena are well known in the first moments of photo- 

 synthesis, being especially marked after long dark periods, under 

 anoxic conditions, or in the presence of high CO2 concentrations. 

 They are much less conspicuous, though also present, under altera- 

 tions of light intensity, but seem to have been little investigated 

 when the wavelength of illumination is altered (under constant in- 

 tensity or effectiveness). The latter situation has been studied in 

 several marine red algae, yielding time courses which may be desig- 

 nated "chromatic transients." 



The method was essentially that of Blinks and Skow (1) using the 

 polarographic or amperometric oxygen cathode (stationary platinum 

 electrode polarized at 0.5 volt). The tissue was held in direct contact 

 with the electrode by a strip of permeable cellophane (cf. Haxo and 

 Blinks (3)). Measurement was by Leeds and North rup "Speedomax," 

 which recorded the potential across a decade resistance inserted in 

 the polarographic circuit. Oxygen diffuses across the tissue from the 

 surrounding sea water (which can be aerated and/or flowing) setting 

 up a steady current flow, after initial polarization has occurred. This 

 is the base line in the dark, representing the respiration of the tissue 

 by the distance below compensation point (dashed line in Figs. 1 and 2). 

 On illumination (by grating monochromator) a new steady state is 

 attained (2) (Fig. 1), OA\dng to the diffusion of photosynthetically pro- 

 duced oxygen to the electrode. Since the tissue is usually but one cell 

 thick, diffusion is only across the cell wall, and the response is very 

 rapid, a new steady state being generally attained in less than a 

 minute. 



Under favorable circumstances (active photosynthesis in very thin 

 thalli) a difference in time course with red algae can be observed be- 

 tween illuminations with red and with green light. An example is 

 shown in Fig. I. The initial rate tends to be higher in green hght, lead- 



444 



