io6 



Scientific Proceedings (112). 



50 (1632) 



Maximum values of osmotic concentration in plant tissue fluids. 



By J. ARTHUR HARRIS, R. A. GORTNER, W. F. HOFMANN, 

 and A. T. VALENTINE. 



[From the Carnegie Station for Experimental Evolution, Cold Spring 

 Harbor, N. Y., and the University of Minnesota, St. Paul, 

 Minnesota.] 



The observations of a number of botanists have shown that 

 extremely high concentrations may characterize plant tissue 

 fluids, especially when the plants 1 occur in a highly saline sub- 

 stratum. To Fitting 2 belongs the credit of first demonstrating 

 that extremely high osmotic concentrations are found in some 

 desert plants, 3 although Drabble and Lake 4 and Drabble and 

 Drabble 5 had preceded him in showing the fundamental relation- 

 ship between environmental conditions and the osmotic con- 

 centration of plant tissue fluids. 



As early as 1902 Cavara reported cryoscopic determinations 

 on saps of high concentration 6 and in 1905 gave results in full 7 

 for a large series of determinations made at Cagliari. His maxi- 

 mum values were found in the sap of halophytes growing in locali- 

 ties where the concentration of the soil solution progressed with 

 the advance of the season. He reports freezing point depressions 

 of 7.25 0 in Obione portulacoides , 7.48 0 in Salicornia fruticosa, and 

 7.25 0 to 8.50 0 in Halocnemum strobilaceum. His determinations 



1 Our present observations apply to the tissue fluids of flowering plants only. 

 No attempt is made here to discuss the concentrations found in such lower organisms 

 as those studied by G. J. Peirce (Pub. Cam. Inst. Wash., 1914, No. 193. P- 47-69) 

 or G. Senn (Verh. Schw. Naturf. Ges., 191 1, xciv). 



2 H. Fitting, Zeitschr. f. Bot., 1911, iii, 209-275. 



3 Fitting found a number of species of plants in the North-African deserts, the 

 leaf cells of which were not plasmolyzed by 3 gram molecular KNO3 solution. The- 

 oretically potassium nitrate of this concentration should be the equivalent of about 

 100 atmospheres. The technical difficulties of applying the plasmolytic method are 

 such as to lead one to question its value as a means of investigating in a quantitative 

 manner the unusually high concentrations found in desert plants. 



4 E. Drabble and H. Lake, New Phytologist, 1905, viii, 189. 

 5 E. Drabble and H. Drabble, Biochem. Jour., 1907, ii, 117- 



6 F. Cavara, Rendic. Congr. Bot. Palermo, 1902, 66. 



7 F. Cavara, Contrib. Biol. Veg., 1905, iv, 41-84. 



