210 Mineral Nutrition of Plants 



concentration of a dilute salt solution, the rate of accumulation is like- 

 wise greater. A corresponding, though not necessarily proportional, 

 increase in respiration is generally observed. These effects are graphi- 

 cally represented in Figures 13 and 14 from Ulrich (85) ; see also Figure 

 15. In Figure 13 it may be observed that the rates of accumulation of 

 the ions of a particular ion pair supplied (here, potassium and bromide) 

 may be rather similarly affected. However, the relative rates of anion 

 and cation accumulation may be distinctly different. Thus, a monoval- 

 ent ion (cation or anion of a pair) usually accumulates more rapidly 

 than a divalent "partner." This may be seen by comparing the absorp- 

 tion of bromide and calcium from calcium bromide or potassium and 

 sulfate from potassium sulfate shown in Table II (84). Further, the 

 rate of absorption of a particular ion is markedly influenced by the 

 nature of the accompanying ion of opposite charge. Thus, bromide 



*NH3 + AMIDE -N 



0.0025 



O.OI25M CaBr, 



CONCENTRATION 



Figure 14. Effects of calcium bromide concentration on 

 the metabolic activity of excised barley roots maintained at 

 25.0 C. for eight hours. Data expressed in the same way 

 as in Figure 13. Conditions of growth and experiment were 

 the same as for Figure 10, except that CaBr 2 only was sup- 

 plied in the experimental culture solution. — Ulrich (85) 



