NO. 



l6 CARBON DIOXIDE ASSIMILATION HOOVER ET AL, 



17 



rate. It thus appears, for the condition of this experiment, that 

 carbon dioxide may be the limiting factor for the high Hght intensities, 

 assimilation being proportional to the carbon dioxide concentration 

 over a considerable range. For the high carbon dioxide concentrations, 

 the light intensity may be the limiting factor, assimilation being 

 proportional to the light intensity. There exist well-defined regions 

 over which the assimilation seems to depend upon both factors. 



Fig. 8.=— Light-assimilation curves derived from Figure 7. 



Ordinates, carbon dioxide assimilated. Multiply by 0.025 to obtain cubic 



centimeters per minute. 

 Abscissas, light intensity. Multiply by 3.56 X 10"^ to obtain watts/cur. 



Alultiply by 4.96 to obtain foot-candles. ' 

 Parameters, carbon dioxide concentrations. Multiply by 0.000041 to 



obtain volume per cent. 



Assuming the simplest type of Blackman reaction involving only 

 linear segments, some transition range is to be expected, since ideal 

 conditions cannot be obtained. Not all the chloroplasts can be main- 

 tained in the same light intensity, nor can all the surfaces of the 

 leaves be brought in contact with exactly the same concentration of 

 carbon dioxide. The fact that the lights are symmetrically placed 

 around the plants not only reduces the fluctuation of intensity over 

 the surfaces of the leaves, but, owing to the fact that the leaves are 

 exposed to radiation from both sides, reduces to a minimum the 



