Relations of Manganese and Other Cations 



195 



The root development of the plants in the culture composed of N/1000 

 CaCl2+N/50 KCl is far more abundant than in the control, N/1000 

 CaCl2, but the top growth is less. It is thus seen that N/50 KCl depresses 

 the growth of the stems. When either N/500 or N/1000 MnCl2 is present 

 with N/50 KCl, in the presence of the weak calcium, the retarding action 

 of the potassium is entirely overcome. 



Manganese is antidoted by potassium, as is shown by Fig. 15 and 

 by the data in Table 12. Slight antagonism results in cultures com- 

 posed of N/50 KCl+N/100 MnCl2+N/1000 CaCl2. Greater protective 

 action exists when the above amount of potassium is present with either 

 N/500 or N/1000 MnCl2. Considering the top growth of seedlings, 

 mutual antagonism exists between potassium and manganese; consid- 

 ering root growth alone, however, potassium has a protective action 

 toward manganese. 



Potassium and manganese (full nutrient solution) . — The further addition 

 of potassium to a full nutrient solution one tenth as strong as the one 

 employed in the previous experiments, lowers the deleterious action of 

 either N/100 or N/500 MnCl2. The further addition of potassium (N/20 

 KCl) to the nutrient solution also results in an increase of root develop- 

 ment, the lateral roots especially being longer and more numerous than 

 those of the control plants. On the other hand, the top growth is retarded 

 somewhat. The results obtained from these experiments appear in 

 Table 13: 



TABLE 13. Experiment Continued for Thirty Days. Data for Ten Plants 



Composition of solution 



(full nutrient solution as the 



solvent) 



N/20 KCl 



N/20 KCl+N/100 MnCh 

 N/20 KCl+N/500 MnCh 



N/100 MnCU 



N/500 MnCl2 



Full nutrient solution 



Green 

 weight 

 of tops 

 (grams) 



4.85 

 1.45 

 4.60 

 0.85 

 2.15 

 5.15 



Grsen 

 weight 

 of roots 

 (grams) 



4.26 

 1.68 

 3.50 

 1.35 

 3.20 

 3.55 



Total 

 green 



weight 

 (grams) 



9.11 

 3.13 

 8.10 

 2.20 

 5.35 

 8.70 



Average 

 length 

 of tops 



(centi- 

 meters) 



10.0 

 6.0 

 9.0 

 1.5 

 6.0 



13.0 



Average 

 length 

 of roots 

 (centi- 

 meters) 



5.6 

 7.5 

 6.0 

 5.0 

 7.0 

 4.0 



