Lecture 3 —55— Absorption 



as a test ion. It would require considerable time to 

 describe this extensive investigation with its many 

 ramifications which was pursued later in England. 

 For my present purpose it may suffice to say that one 

 general conclusion derived from the experiments was 

 that the well aerated cells at or near the surface of 

 the potato discs possessed a marked capacity to ac- 

 cumulate mobile ions, like potassium and bromide ions, 

 and that this accumulation was dependent on cell met- 

 abolism reflected by, but not stoichiometrically related 

 to, the aerobic production of CO2. In later researches 

 Steward has emphasized also the capacity of the po- 

 tato tuber cells to grow and to synthesize protein as a 

 condition for salt accumulation, that is, that type of 

 salt accumulation which results in increase in total 

 salt content (both cation and anion) content of the 

 cell. 



From the point of view of soil and plant inter- 

 relations paramount importance must of course be 

 assigned to the absorption and accumulation of salt 

 by root cells, and we have given much attention to this 

 subject for some years (Hoagland and Broyer, 1936). 

 In order to simplify the system to be studied many 

 of the experiments have been done on excised roots 

 of young plants, especially roots of young barley plants. 

 An earlier investigator had reported experiments along 

 this line, but he did not succeed in causing his excised 

 roots to absorb salt actively and concluded that rapid 

 salt absorption is dependent on the attachment of 

 the root to the shoot. Our own first experiments were 

 not very successful, but a simple technique was later 

 developed for the production of excised roots that had 

 a remarkably high capacity for accumulating certain 

 ions, notably potassium, halide and nitrate ions, over 

 a limited, but adequate period of time for the purpose 

 of the experiments. 



Within a relatively few hours the salt content of 

 the roots could often increase by several hundred per 

 cent. Thus we had admirable material for the study 



