OSMOTIC CONCENTRATION IN PLANT TISSUE FLUIDS. 3 



bed of the ancient Lake Bonneville, should furnish some indication 

 of the maximum concentration 16 to be found in the leaf tissue 

 fluids of flowering plants. 



While high concentrations were demonstrated in a number of 

 species, the highest was found in the typical salt desert half-shrub 

 A triplex confertifoUa. It alone will be considered. 



Two collections made on the rocky cliffs of Stansbury Island, 

 Great Salt Lake, on July 14 gave freezing point depressions of 

 6.96 and 7.97. If we may use the formula of Lewis, 17 upon which 

 published tables of osmotic concentration have been based, 18 these 

 depressions indicate osmotic pressures of 82.9 and 94.7 atmos 

 pheres respectively. 



The highest concentrations were found in plants growing on 

 the low ridges in the salt-flats 19 along the southern shore of Great 

 Salt Lake. A determination on material collected July 16 gave 

 A = 6.22, P = 74.2. 



On July 1 8 a determination on plants in about the same type 

 of locality gave A = 10.00, P = 118.5. Finally, on July 27 a 

 determination made in this locality on the leaves of this species 

 indicated a freezing point lowering of 13.0. The equation used 

 would indicate a concentration of 153.1 atmospheres. 20 



These determinations show that concentrations measured by a 

 depression of 13.0, presumably the equivalent of 153 atmospheres, 

 maybe found in the tissue fluids of apparently normal leaves. 



16 A difficulty in work on the leaves of desert plants lies in the fact that the 

 maximum concentrations must be expected during the periods of more extreme 

 drought. During such periods the saps may become concentrated by desiccation 

 merely. We know very little concerning the functional activities of such leaves 

 or whether they are retained after the beginning of a period of more adequate mois 

 ture. There is, therefore, the possibility that leaves which are too desiccated to be 

 longer functional may be utilized for determinations and indicate concentrations 

 which are really larger than those in which the metabolic processes of the cells may 

 be normally carried on. We believe that except as specifically indicated, the con 

 centrations here recorded were determined on leaves in fairly normal condition. 



17 G. N. Lewis, Journ. Amer. Chem. Soc., 1908, xxx, 668-683. 



18 J. Arthur Harris and R. A. Gortner, Amer. Jour. Bot., 1914, i, 75-78; 

 Harris, Amer. Jour. Bot., 1915, ii, 418-419. 



19 T. H. Kearney, L. J. Briggs, H. L. Shantz, J. W. McLane, and R. L. Piemisel, 

 Jour. Agr. Res., 1914, i, 365-417, pi. 52-58. 



JO A sample from Atriplex nuttallii showed a freezing point lowering of about 

 14.4, indicating a concentration of 169.3 atmospheres. The leaves appeared more 

 dried than those of Atriplex confertifoUa, and we are inclined to await further measure 

 ments before accepting this constant. 



