Extensions of photosynthetic experimentation 133 



Berlin-Reinickendorf, (Fig. 1). The volume of the small vessel is about 20 c.c., 

 that of the large vessel 120 c.c. 7 c.c. of cell Suspension are inserted into the small 

 vessel through a small stopperable aperture (not illustrated), and 80 c.c. of actino- 

 metric liquid are put into the big vessel. The small vessel is not connected to the 

 large vessel but is held in place by rubber bands. 



The combined two vessels are shaken at a rate of 200 turns per min. A collimated 

 light beam enters through the bottom of the small vessel. The fraction of the light 

 not absorbed leaves the vessel only negligibly (less than 1%) in the back direction, 

 but goes mainly through the upper wall and secondarily the side walls into the 

 actinometric Chamber, where it is completely absorbed, producing oxygen con- 

 sumption. 



Two measurements have to be made, first while the small vessel contains water, 

 and second when it contains the cell Suspension. Let the first pressure change be 

 (^)water and the second ( J/>) ce n s , then if 



<p = Ozjhv = 1, 



then the light transmission through the cell Suspension is 



(zJ/>)cells 



(AP) 



water 



There is the difficulty that = ■- 1 only at low light intensities. At higher light 

 intensities declines. In consequence, the transmission has to be determined at 

 light intensities of 1/15 itmoh quanta per min., as used in earlier calibration 

 experiments (Warburg & Schocken, 1949). Experiments at higher light intensities, 

 corrected by an intensity response curve, are not generally advisable, because of the 

 difficulty of estimating the intensities at which the scattered light enters the actino- 

 metric vessel. 



IX. Results 



With the various extensions of technique described here we have continued to 

 confirm our previously reported results (Warburg & Burk, 1950). With 300 mm. 3 

 of cells per vessel where absorption of the green mercury line is essentially com- 

 plete, a quantum requirement of 4, with fluctuations between 3 and 5, per mole- 

 cule of carbon dioxide consumed or oxygen produced, has been observed. Again, 

 with low light intensities, no influence of timing on yield was noted. The yield re- 

 mained the same whether the light increment was added and removed every 5 

 (or 10 or 15) min., or if the sequence was 1 hr. with increment and 5 (or 10 or 15) 

 min. without increment, and so forth. Again, the assimilatory quotient and the 

 respiratory quotient were either equal or different. Equality of these two quotients 

 is immaterial, and to ask that they should be equal is to misunderstand the equa- 

 tions of the two-vessel method. 



With 50 mm. 3 cells per vessel, that is, about 6.5 mm. 3 cells per sq.cm. of bottom 

 area, about 50% of the wavelength 546 mit was transmitted by the cell Suspension 

 in motion. To obtain the same or greater light action pressure changes, as obtained 

 with 300 mm. 3 of cells, higher light intensities were applied, so high that photo- 



