

m 





DOES THE TEMPERATURE COEFFICIENT OF PERME- 

 ABILITY INDICATE THAT IT IS CHEMICAL 



IN NATURE ? 



W, J. V. OSTERHOUT 



In a recent paper Stiles and Jorgensen 1 state that the absorp- 

 tion of hydrogen ions by tissues of the potato has the temperature 

 coefficient of a chemical reaction (2.18-2.22). They apparently 

 reach the* conclusion that "the substance with which the acid 



19 :~ a. 



reacts is presumably the plasma membrane or some part of it," 

 and that the facts suggest the view "held by Pauli and Sztics, who 

 regard the entrance of ions into the cell as due to the reversibility 



1 



of such a reaction between ions and the plasma membrane." 

 These statements, together with the title of their paper, "The 

 effect of temperature on the permeability of plant cells to the 

 hydrogen ion," indicate that they regard the temperature coefficient 

 found by them as the temperature coefficient of permeability to 

 hydrogen ions. 



* 



This view, if well founded, is of considerable interest, as it 

 ndicates that permeability is chemical 2 rather than physical in 

 nature, since (unless vapor tension is a determining factor) no 

 physical processes are apt to be involved in this case which have a 

 temperature coefficient as high as 2. 3 In view of this the state- 

 ments of Stiles and Jorgensen deserve careful examination. 



It should be noted that the only criterion of permeability 

 employed by them was absorption from a solution. Their method 

 consisted in placing slices of potato in a solution of HC1 and 



'Ann. Botany 29:611. 1915. 



'Browx and Worley (Proc. Roy. Soc. London B. 85:546. 1912) have shown 

 that the temperature coefficient of absorption of water by seeds is 2, but it is not 

 clear whether this applies to imbibition (or other processes) taking place inside the 

 cells, or to the permeability of the protoplasm. If it is really the coefficient of per- 



meability to water, it is by no means necessary to extend this conception to permea- 

 bility to substances other than water. 



3 Cf. Kaxitz, A., Temperatur und Lebensvorgange. Berlin, 19 15 (p. 165). 



I 



317I (Botanical Gazette, vol. 63 





