Lecture ^. 



UPWARD MOVEMENT AND DISTRIBUTION OF 

 INORGANIC SOLUTES IN THE PLANT 



I have considered the question of the absorption 

 and accumulation of inorganic solutes by excised roots, 

 an approach that was found convenient as a way of 

 describing, with the minimum of complicating cir- 

 cumstances, the general nature of the physiological 

 processes of salt accumulation by plant cells. Obvious- 

 ly, in the growing plant, a large portion of the nutrient 

 salt absorbed is translocated to the upper part of the 

 plant, there to serve the functions of growth and met- 

 abolism in the various above-ground organs. 



At one time this upward movement of salts was 

 at least by implication regarded by many botanists 

 as a simple matter. The role of transpiration in the 

 upward translocation of inorganic solutes was fre- 

 quently stressed. I can illustrate the point of view 

 by a quotation from the text on botany of Stras- 

 BURGER : 



"Although a large amount of water is retained in 

 the plant body for the maintenance of rigidity and 

 enlargement of the organs, a still larger quantity of 

 water taken up by the roots passes through the plant 

 merely as a medium for the transport of nourishment. 

 As the watery fluid absorbed by the roots contains 

 salts, oxides and other non-volatile substances in solu- 

 tion, these on evaporation are left in the plant and 

 gradually increase in quantity. 



"All those contrivances in plants, therefore, which 

 render possible or promote evaporation operate chiefly 

 in the service of nutrition." 



