FACTORS AFFECTING SALT ABSORPTION 



61 



60r 



50 



40 



E 30 



9> 20 



Q. 



=3 



10 



0-x 



100 200 300 



[CaBr2], m equiv./L 



400 



500 



200 



o 



k- 



c 

 o 

 o 



o 



^0 



0) 

 o 



150 



100 



/ 



Q. 50 



(b) 



6-4 12-8 25-6 



[Sr**] , m equiv./L 



Fig. 20 (a-b). Interactions between univalent and bivalent ions 

 a. Effects of calcium bromide concentrations on absorption by excised barley 

 roots of K+ (O — O) Ca++ (x— x) and Br" (□— □) from solutions of 

 0-005 M. potassium bromide, containing varying amounts of calcium 

 bromide (redrawn from Viets, 1944); b. Effects of strontium concentration 

 on absorption of rubidium by carrot disks in 5 min (O — O) and 24 hr 

 (x — x) (redrawn from Middleton and Russell, 1958). 



more slowly (Fig. 20d). This is explained by supposing that calcium 

 is taken up by two separate mechanisms one of which is strongly 

 inhibited by potassium and the other less so. 



The effect of strontium ions on absorption of rubidium by 

 carrot disks was examined by Middleton and Russell (1958). They 

 found that in a short experimental period, rubidium uptake was 

 depressed by increasing strontium concentration, presumably 



