RELATION OF NUTRIENT SOLUTION TO COMPOSITION 

 AND REACTION OF CELL SAP OF BARLEY 



D. R. HOAGLAND 



In recent years considerable attention has been given to the 

 cell sap from different plants, especially as influenced by varying 

 soil and climatic conditions. Some very interesting general 

 relations have been brought out, but in these experiments it has 

 not been possible to ascertain or control the exact concentration 

 and composition of the soil solution. McCool and Millar (4), 

 however, have made numerous measurements of the freezing point 

 depressions of the cell sap of both tops and roots of plants growing 

 in soils and nutrient solutions of varying osmotic pressure. These 

 researches have shown clearly that the sap of the plant, particularly 

 of the roots, reflects the concentration of the nutrient solution, 

 whether in the soil or in water cultures. 



Comparatively few measurements of the conductivity of the 

 cell sap have been made, although some data concerning this 

 point are quoted by Atkins (i). The H ion concentration and 

 chemical analysis of the sap have received still less study, yet all 

 these determinations are of the greatest importance in soil fertility 

 investigations. The total osmotic pressure in the plant is known 

 to be dependent to a considerable extent on intensity of photo- 

 synthetic action, as well as on the nutrient solution, while the 

 inorganic constituents may well have a more direct relation to 

 the surrounding media. 



For a number of years this laboratory has been engaged in the 

 investigation of the relation between the growth of the barley plant 

 and the composition and concentration of the soil solution as 

 shown by analyses of water extracts and freezing point determina- 

 tions by the method of Bouyoucos and McCool (2). The work 

 with soils has made it evident that the soil solution is of paramount 

 importance in its effect on crop growth, while, on the other hand, 

 the plant has a marked influence on the concentration and com- 

 position of the soil solution. It soon became apparent that the 

 297] [Botanical Gazette, vol. 68 



