Originally published in Biochem. J., 17, 439 (1923). 



89. THE ABSORPTION AND TRANSLOCATION OF LEAD 



BY PLANTS 



George Hevesy 



From the Institute of Plant Physiology of the Agricultural High School, and 

 Institute of Theoretical Physics of the University, Copenhagen 



The investigation of the absorption of lead by plants can be carried out 

 quite simply by dipping them into a solution which contains a radio- 

 active isotope of lead, and determining the radioactivity of the ash 

 from various parts of the plant. In addition to its simplicity and the 

 extraordinary rapidity with which the work can be carried out this 

 method possesses the following advantages : (a) By mixing suitable 

 amounts of ordinary lead with the radioactive lead isotope, one can 

 vary the lead concentration of the solution, as it were, between very 

 wide limits. The assimilation of lead from a Nj\ solution can be just 

 as radily investigated as that from a solution many million times more 

 dilute, (h) One can follow the change in localisation of the lead taken 

 up by the plant, and thence draw conclusions as to the nature of its 

 combination. 



The experiments described in this paper were so carried out, that the 

 plants, which had l)een cultivated in a culture solution, w^ere washed 

 with distilled water, and then the roots were immersed from 1 to 48 

 hours in a solution containing a mixture of lead nitrate and thorium 

 B nitrate. In most cases Vicia faha (horse-bean) was used. After this 

 period of immersion the individual parts of the plant were first well- 

 rinsed with distilled water, and then ignited, and the intensity of the 

 radioactivity of the ash was determined by means of an electroscope. 

 This latter magnitude gives directly the lead content of the ash and thus 

 also that of the corresponding part of the plant, when we know the radio- 

 activity and the lead content of the solution in which the plant has 

 been immersed. 



Thorium 5 is a transformation product of thorium emanation, and is 

 obtained in a very simple manner. A piece of platinum foil is charged 

 negatively to a potential of 110 volts, say, and suspended in a vessel con- 

 taining the preparation (radio-thorium, thorium A", etc.) from which the 

 thorium emanation is generated. Under these circumstances the thorium 

 B collects on the platinum surface, and can be removed with the aid 

 of a few drops of dilute nitric acid. The normahty as regards lead of a 



