PLANTS WHICH REQUIRE SODIUM 



W. J. V. OSTERHOUT 



(with two figures) 



■ 



It has long been customary to regard sodium as necessary for 

 animals but not for plants. In the light of our present knowledge 

 of the role of inorganic salts, it is clear that this distinction between 

 plants and animals is of fundamental importance, if it be true in all 

 cases; but if exceptions occur, its significance largely disappears. 



i 



The experiments which are described here were undertaken in 

 order to learn whether there are cases in which sodium is as neces- 

 sary for plants as for animals. 



One flowering plant was studied, and several genera of algae, 

 among which were representatives of the green, brown, and red 

 algae. The investigation included species from the Atlantic and 

 the Pacific. 



The method consisted in replacing the NaCl of the sea water by 

 one of the following substances in turn: NH 4 C1, CsCl, RbCl, Li CI, 

 KC1, MgCl 2 , CaCl 2 , SrCl 2 , BaCl,, 1 MgS0 4 , and K 2 S0 4 . After some 

 preliminary experiments it became evident that the best substi- 

 tutes for Na are Ca, Mg, and K. An attempt was then made to 

 get better results by using these as substitutes for NaCl in the 

 following combinations (the figures refer to molecular proportions 

 as shown in the table): 500 MgCl 2 +5oo CaCl 2 , 250 MgCk+750 

 CaCl 2 , 500 KCl+500 CaCl 2 , 667 KCl+333 CaCl 2 , 910 KCl+91 

 CaCl 2 . 



All the salts were carefully tested before using and were recrys- 

 tallized when necessary. The water was twice distilled from glass 

 without the use of rubber or cork stoppers; in place of these a 

 plug of absorbent cotton was employed. The water thus pro- 

 duced was not toxic to such test objects as Spirogyra and the root- 

 hairs of GypsophUa, and its quality was further shown by the fact 



1 The introduction of BaCl 2 and SrCl 2 produced precipitates of BaS0 4 and SrS0 4 

 which were allowed to remain at the bottom of the dish during the experiment. 



Botanical Gazette, vol- 54] 



[53 2 



