Hoagland 



— 64 — 



Plant Nutrition 



the relatively high concentration of salt in the culture 

 medium, little potassium or bromide entered the roots, 

 relative to the external concentration, when purified 

 nitrogen was bubbled through the solution. Concen- 

 trations in the sap did not rise to the outside level. 

 The cells behaved as though their permeability to salt 



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TIME IN HOURS 

 Textfigure 14. — Influence of aerobic conditions on salt 

 accumulation by excised barley roots, from solutions of rela- 

 tively high concentration. Initial concentration of potassium 

 ions in external solution was higher than in sap of roots, but 

 little potassivun was absorbed in the absence of oxygen. With 

 oxygen, concentration of potassium in sap rose to much higher 

 level than in external solution. (From Hoagland and Broyer, 

 1942). 



was very low. Under an aerobic condition the effect 

 was notably different. Both potassium and bromide 

 entered the cells rapidly. The concentration of potas- 

 sium became much higher in the sap than in the ex- 

 ternal medium, even though the concentration of the 

 latter was relatively large. Bromide ions accompanied 

 the potassium ions in not far from equivalent quantity. 

 Before carrying the discussion farther I wish to 

 draw your attention to the experiments of Blinks 



