Lecture 3 



— 57 — 



Absorption 



relation of root weight to shoot weight in the barley 

 plants was notably influenced by variations in the 

 natural illumination. The high proportion of root to 

 shoot characteristic of summer grown plants could 

 not be reproduced in the winter season by any manip- 

 ulation of the culture medium. Extending the period 

 of illumination with Mazda lights was also inejffective. 



I I INITIAL CONCENTRATION IN SAP 



B CONC. AFTER ABSORPTION WITH N^ 

 B CONC. AFTER ABSORPTION WITH AIR 



< 



z 

 cr -z 



Ld o 



Z V) 



o 



Textfigure 10. — Showing essentiality of aerobic metabolism 

 for accumulation of potassium, halide and nitrate ions by ex- 

 cised roots of barley plants. By accumulation of ions is meant 

 building up in the sap a concentration higher than that of the 

 external solution. The conductivity of the sap rose to a much 

 higher value than that of the solution under aerobic conditions, 

 but not under anaerobic conditions. 



One of the indispensable requirements for salt 

 accumulation (movement of salt against a gradient) 

 by excised barley roots is a supply of oxygen. The 

 process is one definitely dependent on an aerobic met- 

 abolism, as is the accumulation of salt by potato discs. 

 The stirring of the solution incident to aeration and 

 the removal of CO2 are also factors, but salt accumula- 

 tion does not take place when CO2 is removed by nitro- 

 gen gas bubbled through the solution. A fairly high 



