Assimilation in tenth-milligrams 
of CO, per 50 sq. cm. 
148 Ingvar Jorgensen and Walter Stiles. 
of temperature had no effect on the rate of assimilation. This remain¬ 
ed the same right up to 33°C. The accompanying curve (Fig. 8) 
shows the result obtained with unit intensity of light. It will be 
observed that it resembles the curves shown in Fig. 5 illustrating 
the action of a limiting factor. It is evident that this would be 
the result if the intensity of light were acting as a limiting factor 
over that part of the curve above 3°C. 
Fig. 8. Curve illustrating effect of temperature on assimilation of Cherry 
Laurel with unit intensity of light. The broken curve indicates the respiration. 
(After Matthaei). 
Consequently, if the light intensity is doubled, one would 
expect tne first part of the curve to be much longer, and increase 
in temperature to produce a corresponding increase in assimilation 
until this has reached a value twice as great as that given by the 
horizontal part of the curve when unit intensity of light is 
employed. Similarly, if the light intensity is still further increased 
a yet higher temperature has to be employed before the limiting 
action of light will become evident. 
The curves shown in Fig. 9 illustrate this clearly. They show 
graphically the results obtained by Miss Matthaei for the relation 
between temperature and assimilation when 1, 2 and 4 units of light 
intensity were employed. They indicate that provided light is not a 
limiting factor and the carbon dioxide supply kept constant and in 
excess, the higher the temperature, the greater the assimilation. 
Increasing the temperature will, however, produce no change in the 
rate of assimilation if the light intensity is below a certain value and 
so acting as a limiting factor. 
