96 



MINERAL SALTS ABSORPTION IN PLANTS 



60 r 



3 

 cr 



E 20 



External concn. 



M 



Fig. 34. a. Concentrations of sodium ( — ,---) and bromide ( , — • — • — ) 



in the protoplasm ( , ) and sap ( , — • — •) of Nitella after immersion in 



001 M sodium chloride labelled with radioactive sodium, and 0-01 M sodium 

 bromide labelled with radioactive bromide for 24 hr (redrawn from Brooks, 

 1940); b. Relationship between the apparent free space of bean root tissue and 

 the external concentration of potassium chloride. Points plotted are means 

 and standard deviations of experimental results and the full lines represent the 

 theoretical relationship between AFS and external concentration based on 

 the establishment of Donnan equilibria O — O = 5 mm of root apex ; • — # = 

 section of root 2-3 cm from the apex (redrawn from Hope, 1953). 



