1950 



KINETICS OF PHOTOSYNTHESIS 



CHAP. 37d 



because of continuous chlorophyll synthesis; therefore, only the gas ex- 

 change in the first hour was used to calculate the quantum requirement. 

 A value of 4.3 was obtained in this way for I/7', where 7' is the "net" 

 quantum yield, uncorrected for respiration. In shorter experiments, with 

 light intensity varied so as to overcompensate respiration by a factor be- 

 tween 5 and 40, l/V'-values between 4.2 to 5.2 have been found, corre- 

 sponding to (respiration-corrected) l/7-values between 3.4 and 4.9. 



120 180 240 300 360 



>■ minutes 



Fig. 37D.28. Effect of weak blue-green light (0.013 peinstein/min.) on oxygen lib- 

 eration by Chlorella in red light (0.73 jueinstein/min.) (after Warburg 1954). Solid 

 line: red + blue-green; broken line: red only. Figures indicate net quantum re- 

 quirements (1/7') per molecule oxygen at times indicated by arrows. 



The photosynthetic ratio, Q( — AO2/ACO2), was about 0.9 in all experi- 

 ments, except a single one in which this ratio became infinitely large (ACO2 

 = 0) after the first 1 V2 hours; this was explained by assuming deterioration 

 of the cells in one of the two vessels, making the use of two-vessel equations 

 in the calculation of I/7 inappropriate. 



The effect of weak blue-green light, illustrated by fig. 37D.28, was dis- 

 covered by Warburg et al. as the result of inquiry into the differences in the 

 efficiency of Chlorella cultures grown in daylight (supplemented by in- 

 candescent light) in summer and in winter; and into the — previously de- 

 scribed — capacity of white background light to assure constant high ef- 

 ficiency of added red light {cf. above p. 1941). Warburg had suggested 



