BRIGGS: THE LIVING PLANT AS A PHYSICAL SYSTEM 



95 



Integrating this equation and transforming to common log- 

 arithms, we have 



logioft = at + c (7) 



in which c is the logarithm of k when t = 0, that is at the be- 



1 



1 



1 

 1 



1 



I 

 I 



.24 

 22 



20 



/<? 



/6 

 ,/4 



/<? 

 /O 

 08 



.06 



04 



02 



§1 



o / 



9/9 

 ^__ ° / 



h^^ 



o ~Z^* o 

 So 



24 26 26 30 2 4 6 & 



<JO/VE /S/4 iJULy 



/O /2 



Fig. 2. Daily change in the ratio of transpiration to evaporation during 

 early growth of Sudan grass. Circles represent observed ratios. Solid line 

 computed from relationship in figure 1. After Briggs and Shantz. 



ginning of the period under discussion. Expressing (7) expo- 

 nentially, we have 



k = 10 at + c = k -10 at (8) 



Therefore, if the logarithms of the daily transpiration-evapo- 

 ration ratio, when plotted against the time, form a straight line, 

 the condition expressed in equation (6a) is satisfied, and the 



