Toxicity of Various Cations 



207 



Toxicity of barium 

 The writer has presented data by means of which it was demonstrated 

 that barium ions when present in distilled water are extremely deleterious 

 to pea seedlings. The data given below lend further emphasis to this 

 point. Although N/4000 BaCl2 is the lethal concentration for roots of 

 pea seedlings, great injury results from far more dilute solutions. It 

 will be noted in Table 6 that N/10,000 BaCl2 retards root development. 

 In a full nutrient solution the same root retardation is secured only with 

 N/20 BaClo. The toxicity of barium is of course greatly depressed 

 when present m full nutrient solutions or in soil cultures. 



TABLE 6. 



Experiment with Canada Field Pea Seedlings. 

 Data for Ten Plants 



Duration, Ten Days. 



Composition of solution 



Increase in 

 length of tops 

 (centimeters) 



Increase in 

 length of roots 

 (centimeters) 



Distilled water as the solvent 



N/3,000 BaCh 



N/4,000 BaCl2 



N/5,000 BaCl2 



N/10,000 BaCl2 



Distilled water 



FuU nutrient solution as the solvent 



N/6BaCl2 



N/10 BaCl2 



N/20BaCl2 



N/100 BaCl2 



Control 





 



Slight 

 2.5 



7.5 



. 

 



2.5 

 5.0 



8.5 



Toxicity of strontium 

 Strontium exhibits a rather unusual behavior toward seedlings. Com- 

 paratively dilute solutions in distilled water are extremely injurious, but 

 very strong solutions are required in order to prevent growth. For 

 example, N/2000 SrCl2 greatly retards the gro^\i;h of the roots of pea 

 seedlings, but roots are not killed when placed in solutions of N/7 SrCl2, 

 slight development resulting. 



I 



