T. C. Broyer 



209 



Inorganic solute supply 



The supply of mineral salts is axiomatic. Furthermore, the con- 

 centration and relative proportions of such substances may alter or 

 control internal processes. Again, the inorganic solute status may modify 

 the rates of the two processes earlier referred to, namely, accumulation 

 and respiration. The effect to be noted is that of concentration of a 

 single salt in the bathing medium on the rates of respiration and of 

 accumulation of the ions of the compound supplied. With increasing 



pH 

 7.0 



6.0 



5.0 



4.0 



0.005 



0.025M KBr 



CONCENTRATION 



Figure 13. Effects of potassium bromide concentration on 

 the metabolic activity of excised barley roots maintained 

 at 25.0 C. for 8 hours. K and Br values given as milli- 

 equivalents per liter of expressed sap. R.Q. = C0 2 /0 2 ; 

 Sugar — total sugars expressed as grams glucose per liter of 

 expressed sap. The following are given as milliequivalents 

 per liter of sap: O.A. (total nonvolatile organic acids) and 

 NH 3 -f- amide-N (ammonia plus amide nitrogen). pH 

 values were determined on expressed sap. Conditions of 

 growth and experiment were the same as for Figure 10, 

 except that KBr only was supplied in the experimental cul- 

 ture solution. — Ulrich (85) 



