3{j() Univer.sitjj of California PubJicatioHs in AfiriruUural Sciences [Vol. 1 



THE ABSORPTION OF SALTS FROM THE CULTURE MEDIUM 



The absorption by plants of salts from a solution is no doubt 

 intimately related to the composition of the solution, since the 

 intake of inorganic salts occurs only when the concentration of 

 the solute outside the permeable protoplast is greater than that 

 within. Hence the total osmotic concentration of a solution may 

 affect the intake and storage of the salts from the solution. ^^ 

 The quantity of salts which are absorbed by the plant may also 

 vary with the qualitative composition of the solution. Thus True 

 and Bartlett^- have shown that absorption from a solution of two 

 or of three salts is more rapid than from a solution containing 

 a single salt. It is evident that the factors wdiich regulate ab- 

 sorption are very complex, and that this complexity increases 

 with an increase in the number of different anions and cations 

 in the solution. It is further evident that two methods may be 

 followed with a view to ascertaining the quantities of salts ab- 

 sorbed. The ash of the plants may be analyzed or the residue 

 of salts remaining in the culture may be determined. It has 

 seemed desirable to attempt a study of absorption in the present 

 case by means of the latter method. 



Method of Analysis 



The small quantities of salts added to each pot made the 

 acid-extraction method undesirable, since the large quantities of 

 sand required to give weighable precipitates would have been 

 extremely hard to dehydrate, thus introducing a considerable 

 source of error. For this reason the colorimetric method of 

 analysis'^^ was used in this work. An exception was made in the 

 determination of calcium, which was made by the usual volu- 

 metric method. The sulphur was determined gravimetrically as 

 BaSO^. A water extract was prepared from 250 g. of sand by 

 leaching \\\\\\ successive small portions of distilled water until 



31 Livingston, The role of diffusion and osmotic pressure in plants, 

 Chicago, 190.3. 



32 True and Bartlett, U. S. Dept. Agric. Bur. Plant Ind. Bull. 231, 1912, 

 and Am. Jour. Bot., vol. 2, pp. 255-278, 311-323, 1915, vol. 3, pp. 47-58, 

 1916. 



33 Schreiner and Failyer, U. S. Dept. Agric. Bur. Soils, Bull. 31, 1906. 



