xu,c,2 Brown and Heise: Carbon Dioxide Assimilation 87 
derived from the available experimental data. If the photo- 
chemical process in carbon dioxide assimilation could be studied 
independently of all complicating reactions it might well show 
a direct proportionality between light intensity and reaction 
velocity, but the experimental evidence at hand does not prove 
that such a relation holds for photosynthesis as it takes place 
under natural conditions. 
One of the most extensive investigations on the relation of 
carbon dioxide assimilation to light intensity is that of Reinke, 
who worked with Elodea.(18) In Table I we have summarized 
Reinke’s Table VIII, using the average of all his values for as- 
similation with any given intensity of light. This is Reinke’s 
longest and probably his most important experiment. 
TABLE I.—Summary of Reinke’s Table VIII, showing the relation between 
light intensity and bubble emission. 
Lightintenatty. [rm tegen thee ee ee 
In se 
Fullsun-| yssun- | In 15 fear fbn In 15 Bomnpre va Avenas 
light=1. | light=1. | seconds. mie hack, of light. seconds, pret hay of light. 
Ys 1 5.5 5.5 5.5 
é 2 7.5 2.0 3.7 
i 4 11.0 2.7 2.7 8.7 a2 a: 
; 8 18.5 1.9 2.3 15.0 1.6 1.9 
1 16 27.0 L1 1.7 23.2 1.0 1.4 
? 82 35.0 0.5 Lt 29.7 0.4 0.9 
} 64 39.0 0.1 0.6 380.2 0.02 0.5 
g 128 38.2 0.0 0.3 31.5 0.02 0.2 
y 256 39.0 0.0 0.1) 815 0.0 0.1 
Obviously the foregoing data show no simple direct propor- 
tionality between assimilation and light. Instead there is for 
each increase in light intensity a progressively smaller increase 
in the assimilation velocity. This progressive falling off in as- 
similation per unit of increase in light is very rapid, and it 
is, therefore, not surprising that with high light intensities 
increasing the intensity does not greatly augment the rate of 
assimilation. 
In Table II we have calculated the increase in bubble emission 
per unit of light for Reinke’s different tables. These results are 
in agreement with the more detailed calculations given in Table 
I for Reinke’s Table VIII. 
