1958 



KINETICS OF PHOTOSYNTHESIS 



CHAP. 37D 



least up to a certain cell density. The cumbersome integration procedure 

 could therefore be replaced, in most experiments, by multiplication with a 

 constant proportionality factor, care being taken to assure unchanged 

 aUgnment of the beam (to which the proportionality factor is sensitive) . 



About 0.66 lA. of cells was used, suspended in about 0.4 ml. of potassium 

 chloride solution, equilibrated with 5% CO2; the (incident) intensity was 

 from 0.25 to 0.015 Meinstein/(cm.2 X min.). (The compensation point 



3 6 9 12 



MINUTES 

 Fig. 37D.30. Polarographic record of oxygen exchange in 3 min. light-3 min. dark 

 cycle (after Brackett et al. 1953). / (incident) = 8.35 X IQ-^ watt/cm.^, X 578 m^; 

 dilute suspension of Chlorella pyrenoidosa (about 1.5 ^1- cells/ml.), T: tangent to curve 

 laid through three adjacent points. 



was at about 0.07 jueinstein.) Fig. 37D.30 shows a typical reading for a 

 3 minute dark-3 minute light cycle. The rates were determined either by 

 the "best straight line" approximation of a whole light or dark period, or by 

 fitting tangents to curves laid through three adjacent points; a typical re- 

 sult of the second procedure (for a six minute cycle) is shown in fig. 37D.31. 

 This figure also illustrates the reproducibility which was regularly obtained 

 with several samples of the same culture. 



Respiration in fig. 37D.31 shows typical changes with time. When the 

 illumination starts after an extended period of darkness, the respiration is 

 low. It increases after each light period and dechnes again in each dark 

 period. The decline is sharp in the first half-minute of darkness; the 

 oxygen uptake then increases again slightly, exhibiting a flat maximum 1 or 

 2 minutes after darkening. It then dechnes slowly and approximately 



