ATOAHC DYNAMICS OF PLANT GROWTH 



885 



If we noW' determine by both chemical and. radioactive analysis the 

 phosphorus content of, for example, ash obtained after ignition of a 

 leaf, we can determine how much of the total phosphorus present origi- 

 nated from the culture solution, that is, the "radioactive", phospho- 

 rus', and how much was already present in the plant at the beginning of 



Initial 

 plant- 



Second leaves 



Pirsr leavps 



O) 



t^lanl after 



qrowtli 



Fig L 



^he experiment. The result of the chemical and the radioactive analysis 

 is seen in the accompanying table. 



The chemical analysis was carried out by the colorimetric method 

 described by Lohmann and Jendrasik^-\ and the radioactive analysis by 

 comparing the activity of the ash of leaf or stem with Ihat of a known 



