The Plant as a Metabolic Unit 



235 



t 7 



« 6 

 u 



> ^ 



§ 4 

 ui 



E 



z 2 



z ^ 



o 

 o 



N03 



1 



■ PINAL CONCENTRATIONS 

 LJ ORIGINAL CONCENTRATIONS 



HCO1 



H2PO4 



Fig. 4. Relation of water and solute absorption; barley plants (duplicate sets of 

 168) grown for 19 days in a complete culture solution. 



Experimental period of absorption, 24 hours. 



Solutions used, same as described under figure 2. 



Correction made for very slight loss of water caused by evaporation from solu- 

 tion; 825 cc. of water absorbed by each set of plants, from original volume of 

 3900 cc. 



Each set of plants absorbed the following total quantities of the various ions 

 (in milligram equivalents) : 



K 1 1.5 NO3 22.0 



Ca 2.6 SO4 0.6 



Mg 1.5 H2PO4 0.2 



HCO3 determined by titration method. Some organic acid radicles may have 

 been present. 



at a proportionally much faster rate than water and as a neces- 

 sary consequence the nutrient solution becomes diluted with 

 respect to these elements. A recent experiment (fig. 4) illustrates 

 this point. The roots of young barley plants were immersed in 

 an aerated nutrient solution for twenty-four hours, without any 

 addition of water. The arrangements permitted only a very slight 

 amount of water to escape by direct evaporation from the solu- 



