PHOTOSYNTHESIS AND RESPIRATION 



1937 



not all, of the plots). All "wiggles" (except the initial oxygen "gulp") 

 are smoothed if the cells are suspended in 1% glucose solution (+0.1 M 

 KCl) instead of in pure KCl. 



Brackett et at. concluded that the uncertainty caused by the fluctuations 

 of respiration, may account for the "Kok effect" (c/. Vol. II, Part 1, p. 

 1113). If the respiration correction on every point is interpolated as de- 

 scribed on p. 1960, this effect disappears {cf. figs. 37D.33 and 34) and the 

 calculated rate of photosynthesis (uppermost line in fig. 37D.32), becomes 

 proportional to light intensity and constant through the light period 

 (except for an "induction period" of 1-2 minutes). 



Fig. 37D.22. CO2 exchange by Scenedesmus in dark and in light, followed with a 

 pH meter, in saturating light (after Gaffron 1953). Decreasing depth of the troughs 

 shows the decline in yield with decreasing CO2 concentration (increasing pH). Note 

 immediate return to the state of compensation after the switching-on and the switching- 

 off of the light, followed, in dark, by an outburst of respiration. 



These observations of Brackett et at. show qualitative similarity to the 

 results of Warburg et at. in that they, too, indicate an enhancing effect of 

 photosynthesis on respiration, delayed by 1-2 minutes, and therefore "out 

 of phase" with photosynthesis in alternating light. However, quantita- 

 tively the results are quite different, as a comparison of figs. 37D.30 and 

 33. 6A will show (both of which refer to a 3 minute light-3 minute dark 

 cycle). There is nothing in Brackett's broken lines resembling the bends 

 of Warburg's curves, on which the concept of "one quantum process" is 

 based. Rather, Brackett's results confirm the conclusions of Emerson 

 and co-workers about the great variability of respiration. 



Whittingham (1954) was unable to find, by spectrophotometry of the 

 hemoglobin-oxyhemoglobin transformation, any extra O2 exchange by 

 ChloreUa in light-dark cycles of 1-3 minutes. 



While Brackett et al. registered rapidly the changes in oxygen uptake 

 immediately following a period of illumination, Gaffron (1953) did the same 



