62 



MINERAL SALTS ABSORPTION IN PLANTS 



I50r 



3 300q- 



tn 

 a> 



>• 2O0- 



3 



cr 



O) 



100- 



Q. 



ID 



25 



100 



50 75 



[kCL] , m equiv./L 



Fig. 20 (c-d). Interactions between univalent and bivalent ions, 

 c. EflFect of adding calcium chloride (0-01 N) on absorption of potassium 

 ions from different concentrations of potassium chloride by excised barley 

 roots (redrawn from Overstreet, Jacobson and Handley, 1952); d. Effects of 

 adding potassium chloride at various concentrations on absorption of calcium 

 from 0-005 N. calcium chloride by excised barley roots (redrawn from 

 Overstreet, Jacobson and Handley, 1952). 



through competition for physical binding sites. Over a longer 

 period, however, rubidium absorption was enhanced by the presence 

 of strontium through an effect upon metabolic absorption (Fig. 20b). 

 Synergistic effects are not confined to those between univalent and 

 bivalent cations. Fawi-y et al. (1954) found that trivalent ions, e.g. 

 aluminium, cerium and lanthanum, stimulate uptake of univalent 

 cations in excised barley roots. 



