184 Plant Physiology 



BALANCED SOLUTIONS 



Since the early studies upon the mineral nutrients of 

 plants, it has been more or less apparent that any one of 

 the nutrient salts employed singly may be injurious, or 

 may inhibit growth. The extent of this inhibition of 

 growth has in recent years been more extensively meas- 

 ured. Moreover, it has long been realized that in the 

 preparation of the nutrient solution a certain ratio of the 

 different salts is required, or may be favorable, for the best 

 results. 



It is now known that there are certain interesting antag- 

 onistic relations between some of the nutrient and other 

 bases whereby the inhibitory effects of one may be in part 

 or entirely counterbalanced by the presence of another. 

 A solution in which the inhibitory or toxic action of one 

 substance is rather effectually eliminated by an " antago- 

 nistic " compound is now generally termed a balanced solu- 

 tion. Some cases of alleged antagonism are apparently 

 complicated by factors of nutrition and exosmosis, but 

 at present it is not possible to evaluate the different 

 factors. 



101. The injurious action of certain basic nutrients. 

 Although toxic action in general is discussed at length 

 later, it is necessary here, in connection with balanced so- 

 lutions, to note the relations of some plants to some of the 

 several single nutrient compounds. The following table, 

 from data by Kearney and Harter, shows approximately 

 the limiting concentrations of two sodium and two mag- 

 nesium salts, endured for twenty-four hours by wheat, 

 lupine, and maize : 



