94 



Mineral Nutrition of Plants 



3.00 



5 



§2.00 



6 



K 1.00 



I 



3 4 5 6 7 



MM. FROM ROOT APEX 



8 



10 



ri3i 



Figure 3. Graphs showing the distribution of absorbed P 32 and I loi in 

 barley roots as a function of distance from the root apex. The dotted line 

 labeled "external solution" corresponds to the activity of a volume of the 

 bathing solution equal to that of 1 mm. of root segment and is arbitrarily 

 given the value of 1.00 in the graph. All other amounts are given in terms 

 of the value of the external solution. — Overstreet and Jacobson {38), and 

 Jacobson and Overstreet (23). 



Hypotheses concerning the chemical nature of R-H and R'-OH 



On the basis of certain investigations dealing with the mechanism 

 of ion accumulation by plant cells, Osterhout (j6) postulated that the 

 plant substance R-H may be similar in its properties to some of the 

 aromatic alcohols. Osterhout was successful in constructing an artificial 

 model of a cell which consisted of two electrolyte solutions separated 

 by a layer of potassium guaiacolate. By maintaining a difference in 

 hydrogen ion concentration between the electrolyte solutions, he was 

 able to show an accumulation of K-ions in the solution highest in H- 

 ions. No hypotheses were made concerning the substance R' • OH. 



