898 



ADVENTURES IN RADIOISOTOPE RESEARCH 



Ad 2. To I y free P present in the inactive roots corresponds 0.0043 

 p. c. of the 32p added. In the course of one day, 0.068 p. c. of the P 

 was found to have migrated into the inactive solution, thus in 

 the course of 1 day, 15.7 7 originally present in the roots moved 

 into the culture solution. 

 Ad 3. To I y free P present in the inactive roots corresponds 0.0028 

 p. c. of the 32p added. In the course of 1 day, 0.049 p. c. of the 

 P added was found to have migrated into the inactive solution, 

 thus in the course of 1 day, 17.5 y originally present in the roots 

 moved into the culture solution. 

 The following distribution of the ^sp added to three weeks old wheat 

 plants was found to take place 4 weeks after the start of the experi- 

 ment. 



Table 8 



The amount of phosphorus migrating from the roots of different plants 

 into the nutrient solution in the course of one day is seen in Table 9. 



Table 9. — Amount of Phosphorus 

 Migrating from the Roots of Diffe- 

 rent Plants into the Nutrient Solu- 

 tion IN THE Course of one Day 



Amount of phosphorus taken up by the roots 



To determine the amount of phosphorus taken up by the roots of 

 plants of about the same size as those used in the experiments described, 

 we measured the percentage of the ^^P added to the inner solution which 

 accumulated in the plant in the course of 1 clay. From these figures and 

 the phosphorus content of the solution the amount of phosphorus taken 

 up by the roots can be calculated. The results obtained are seen inTable 10. 



