136 University of California Publications in Agricultural Sciences [Vol.3 



nature, we get as a result a solution in which the plant grows and 

 functions normally. Such a solution has been termed by Loeb, "phy- 

 siologically balanced. 



It is evident that if growth is better in a two salt solution the toxic 

 effects of the solution due to a single salt must be lessened by the 

 presence of the second salt. "We may refer to either as the second salt 

 since either may be toxic alone. On the addition of a third salt the 

 increase in growth over that obtained in the two salt solution points 

 to a still further lessening of the toxic properties of the various salts 

 present taken singly. This action of one or more salts in limiting or 

 preventing entirely the toxic effects of one or more other salts, is 

 termed antagonism. Sea water may be taken as an example of a 

 physiologically balanced solution or a solution in which the mutual 

 antagonism between the constituents of the solution is such as to 

 allow of normal growth of numerous organisms. 



The fact of the existence of antagonism has been proven by a 

 number of investigators working in plant and animal physiology, but 

 the mechanism of antagonistic action is by no means clear. Since 

 salts are very largely ionized in the nutrient solutions usually em- 

 ployed, it is probable that antagonism has to do with ions. Further, 

 antagonism will probably take place between the ions present in, or 

 between, the ionic constituents of the solution, and the living mem- 

 branes in contact with the solution. Loeb 1 first advanced the theory 

 that one ion may prevent the entrance of another ion into living cells 

 and that in this property lies the reason for antagonistic action. On 

 the basis of this hypothesis, penetration precedes the manifestations of 

 toxic effects and where penetration does not occur, due to antagonistic 

 action, there are no toxic effects evident. Used in this way, the term 

 penetration means simply the entrance of ions in greater number than 

 would normally occur were the plant cells in their natural environ- 

 ment. Experimental evidence as to the correctness of this hypothesis 

 has been furnished by Loeb 2 in a very interesting series of experi- 

 ments. Osterhout 3 has applied the electrical conductivity method 

 to the measurement of the penetration of ions into plant tissue, 

 while recently Brooks has confirmed Osterhout's results (1) by deter- 

 mining: the diffusion of ions through tissue, 4 (2) by exosmosis, 5 and 

 (3) by the change in the curvature of tissue. 6 



J Araer. Jour. Physiol., vol. 6 (1902), p. 411. 



2 Science, n.s., vol. 36, no. 932, p. 637. 



?■ Ibid., vol. 35, no. 890, p. 112. 



* Proc. Nat. Acad., Sci., vol. 2 (1916), p. 569. 



sAmer. Jour. Bot., vol. 3 (1916), p. 483. 



