ENERGY EFFICIENCY IN PHOTOSYNTHESIS 271 



analysis (Umbreit et al, 1949; Warburg and Negelein, 1922), but it can 

 be determined indirectly as described presently. 

 The oxygen change is calculated by the formula 



OAI/C02/CCO2 

 2 = 7 1 7 — ' 



and the CO2 change is calculated by the formula 



(l/y)kco^ + koi 



where h is the change in pressure and ko, and kco^ are the vessel con- 

 stants obtained when only one gas is involved. The basic assumption of 

 this method is that 7 remains constant, but there is much evidence that 

 it does not remain constant under the conditions used in the measure- 

 ment of photosynthesis. Under certain conditions carbon dioxide is 

 produced by exposure to light (opposed to photosynthesis), and this 

 "Emerson carbon dioxide burst" produces an excess of carbon dioxide 

 and gives an abnormal value of $^^ when light is introduced into dark- 

 conditioned algae (Emerson and Lewis, 1939, 1941, 1943; Nishimura et al., 

 1951). Additional evidence for such a phenomenon has been supplied by 

 the observation that increased acidity occurs upon illumination (Blinks 

 and Skow, 1938). 



Part of the burst is due to the sluggishness with which the carbon 

 dioxide reaches equilibrium, and part is probably due to physiological 

 conditions. Other workers beUeve that the value of 7 does not change 

 enough to affect their calculations (Warburg, 1948). 



Carbon dioxide and oxygen can be determined simultaneously by the 

 indirect method proposed by Warburg. This method has been very 

 widely used. Two vessels are used which are alike except that the ratio 

 of gas space to the volume of liquid is different in the two. The formula 

 for the change in oxygen concentration is 



AO5 



H K.C02 hkcoi 



/VcOzZ-t^Oj /CcOj/ri'Oi 



and that for the change in carbon dioxide concentration is 



ACO2 = 



flko2 -n/Voj 



where A-o^, kco^, Ko,, and Kco^ are the vessel constants for the two vessels 

 when only the indicated gas is exchanged. The symbol h is the manom- 

 eter reading of pressure differences in the vessel for which the vessel con- 

 stants Av)2 and A:co2 apply, and H is the manometer reading for the other 

 vessel, with the constants Kq., and Kco.. A great many of the measure- 

 ments of photosynthesis have been made by this method, as given in 

 Table 4-1. 



