Lecture 3. 



THE ABSORPTION AND ACCUMULATION OF 

 SALTS BY PLANT CELLS 



In the last lecture I undertook to discuss the chem- 

 ical elements derived from the plant's root medium 

 that are indispensable to the growth of the plant. 

 Manifestly this subject constitutes a fundamental 

 aspect of plant nutrition, but not less fundamental are 

 problems of the entry into the roots of these essential 

 chemical elements and of their upward movement and 

 distribution in the plant. These are the problems I 

 shall deal with in this and the following lecture. 



Interest in this general field of research by the 

 laboratory with which I am associated was initially 

 awakened during the first world war when we became 

 engaged in a comprehensive investigation of the giant 

 kelps of the Pacific Coast, with intent to gain knowl- 

 edge that would be helpful in recovering the then much 

 needed potash present in the kelps. We were im- 

 pressed by the remarkable selective accumulation by 

 these plants of potassium, iodide and bromide and by 

 the lack of satisfactory knowledge concerning the 

 physiological processes that led to the absorption of 

 these ions from the sea water and their differential 

 retention in the plant tissues, apparently largely in 

 inorganic form. The undertaking of special research 

 on this problem came later, however, and was more 

 immediately stimulated by the many questions that 

 arose from the soil researches described in the first 

 lecture. It was evident that these questions could 



