Teinperatiirc. 



73 



of temperature had no effect on the rate of assimilation. This remain- 

 ed the same right up to SS^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 th?it part of the curve above S^C. 



> CJQ 



c •« 



■^ 4) 



-lo 



O* IT X^ 'X'S' 30° Z^'Q, 

 Temperature. 



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 Pig. 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 lifjht 

 intensity were employed. They i ndicate that [[royi'led 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. 



