10 



TRANSLOCATION OF PLANT FOOD IN WHEAT SEEDLINGS 



to stand 24 hours. An analysis of the resultant solution gave 100 

 parts per million of potash, 35 parts per million of phosphoric acid, 

 and 40 parts per million of nitrogen. These figures account in part 

 for the greater proportion of potash that the plant took up even in 

 water culture. The fact that the phosphoric acid found in the plant 

 at the end of 12 days was below that contained in the original seed, 

 simply indicates that while some phosphoric acid is leached from the 

 seeds, the little plants do not require this element at this stage of 

 growth and so do not absorb it to the same extent that they do potash 

 and nitrogen. Figures 1 and 2 are based on results obtained in the 



FIG. 1.- Graph showing decrease in total dry weight of plant and increase in inorganic plant constituents 

 and weight of plumule and radicle. 



first experiment using distilled water cultures, when no special 

 precautions were taken to prevent the seedlings from assimilating 

 the extraneous salts. 



The amount of potash above 100 per cent absorbed by the plant, 

 due to the leaching out of this element from ungerminated seeds, sug- 

 gested a modification of the method of growing the seedlings. This 

 variation consisted in first steeping the seed for several hours, pouring 

 off the water, resteeping in fresh water, and repeating this change of 

 water at shorter intervals about a dozen times, after which the seeds 

 were spread out on the aluminum disks and allowed to germinate. 



