Hoa gland 



— 74 — 



Plant Nutrition 



of the green parts of the plant and it becomes of 

 interest to observe, under several known conditions, 

 the relation of water absorption to salt absorption by 

 the transpiring plant. 



The information sought cannot be obtained by 

 some of the older methods employed in the study of 

 the relation of water absorption to salt absorption or 

 movement; for example, by comparison of the ash 



Textfigure 17. — An early experiment illustrating changes 

 in ionic concentrations in a nutrient solution caused by absorp- 

 tion of water and nutrients by barley plants. Note changes in 

 concentrations of individual ions and appearance of HCO3 ions 

 in appreciable concentration. Thus excess absorption of anions 

 over cations is compensated. (From Hoagland, 1923, redrawn). 



content of plants grown for a long period in shade 

 and in full light. Entirely different types of plant 

 systems are thus developed and the interpretation of 

 data presents too great difficulty and complexity to 

 afford answers to the questions we are now propos- 

 ing. Simple experiments conducted over brief periods 

 of time with initially uniform plants previously grown 

 under appropriate control of nutrition are needed. 



Let us first consider an experiment in which young 

 metabolically active barley plants are absorbing water 



