Originally published in Nature, 139, 149 (1937). 



91. EXCHANGE OF PHOSPHORUS ATOMS IN PLANTS 



AND SEEDS 



G. Hevesy, K. LINDERSTR0M-LANG and C. Olson 



Institute of Theoretical Physics and the Carlsberg Laboratories of Copenhagen 



In a letter to Nature^^^ we communicated the results of experiments 

 carried out on maize plants using radioactive phosphorus as an indicator 

 of the behaviour of the phosphorus atoms. The results obtained showed 

 unambiguously that the greater part of the phosphorus atoms present 

 in the leaves and in the roots of the plants investigated is not permanently 

 in one place, but migrates from leaf to leaf. We extended the experi- 

 ments described above and investigated the behaviour of phosphorus in 

 the sunflower. 



The plant was first grown in an ordinary nutritive solution until a set 

 of leaves, which we will call 'lower leaves', appeared. We then placed 

 the plant in a second nutritive solution in which the phosphorus atoms 

 were replaced by 'labelled' phosphorus atoms (mixed with radioactive 

 phosphorus atoms). The second set of leaves, which we will denote as 

 'upper leaves', were grown in this solution and contained accordingly 

 labelled ('radioactive') phosphorus atoms. For the sake of simplicity we 

 will assume that the 'lower' leaves did not grow further in the second 

 solution but retained their original size; then we must distinguish be- 

 tween two extreme cases: (a) the phosphorus atoms do not migrate; 



Tablk 1 



