QUANTUM YIELD MEASUREMENTS BY THE MANOMETRIC METHOD 1095 



Table 29.1 

 Maximum Quantum Yields of Different Species (after Emerson and Lewis 1941) 



Species 



Green algae: 



Cklorella pyrenoidosa 0.101 9.9 ^ 



Chlorella vulgaris 



Chlorocnccus 



Eudorina 



Sticchococcus had liar is 



Scenedesmus D^ 



Sceriedesmus D^ 



Gyorffiana humicola 



Oocyst is naegeli 



Blue-green algae: 



Chroococcus 0.086 11.6 



Aquatic flowei'ing plant 



Wolffiella limiulata . 060 16.6 l^ /<) 



Rieke, working in Franck's laboratory at Chicago, carried out in 19-11 a 

 series of quantum yield determinations which Avere not published until 

 much later (Rieke, 1949). He used relatively dilute and therefore only 

 partially absorbing Chlorella suspensions, and determined the absorbed 

 light energy by means of an integrating sphere. Because of the compara- 

 tively loM' cell density, the respiration correction was relatively small. 



In experiments of this type, Rieke found quantum yields of about 

 0.08 for Chlorella (in acid solutions as well as in alkaline buffers), and from 

 0.09 to 0.11 for Scenedesmus (in 0.025 M bicarbonate, saturated with 4% 

 CO2, pH 8.4). Somewhat loAver yields (7 = 0.074) were obtained with 

 Scenedesmus in the more alkaline carbonate-bicarbonate buffers. The 

 quantum yields (in buifers) were the same at 10° and 20° C; they were 

 not significantly affected by variations in light intensity during the last 

 days of the culture period (from "very low" up to 10,000 lux), by doubling 

 the salt concentration in solution, by culturing in 4% CO2 or in normal air, 

 and by adding a mixture of micronutrients. It was noted, hoAvever, that 

 groAA'ing the cells to a culture density of over 1 ml. wet cells/1, impaired 

 their photosynthetic efficiency. 



The quantum yields decreased slightly AA'ith increasing light intensity, 

 betAveen 1100 and 4400 erg/cm. ^ sec, e. g., from 0.077 to 0.072 in one experi- 

 ment with Scenedesmus, and from an average of 0.084 at 1900 erg to an 

 average of 0.079 at 4400 erg in Chlorella. 



Wassink (1946) applied Warburg's manometric technique to the meas- 

 urement of photosynthesis in the leaves of several horticultural plants. 

 (Small discs punched out of these leaves AA-ere allowed to float in buffer 

 solutions in a Warburg apparatus.) At Ioaa- or moderate light intensities, 



