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20- 



O. Biddulph 



% gain in P. 



Fe cone of tissues 







t e £ves 



Leaves 



269 



(A 



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P to Fe ratios in the nutrient media 



Figure 4. The percentage gain in phosphorus by parts of bean plants 

 when grown in nutrient solutions 0.00001M in phosphorus but with vari- 

 ous levels of iron. 



phosphorus; rapid entry into the vein system at pH 7.0 and medium 

 phosphorus, but little or no distribution into the mesophyll. This ac- 

 cumulation of iron in the veins is extremely striking and indicates al- 

 most complete immobility. At pH 7.0 and high phosphorus the Fe 55 

 fails to enter the xylem system due to its precipitation at the root sur- 

 faces, so there is little Fe 55 in either veins or mesophyll. The results 

 herein reported indicate that at pH 7.0 and medium phosphorus, rela- 



