Lecture 6 



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Biochemical Problems 



from becoming too acid. Actually it may happen that 

 potassium deficiency leads to a slightly more acid 

 reaction of the sap, despite relatively large calcium 

 and magnesium absoi-ption, a point discussed further 

 in the next lecture. 



Since so much information was at hand on the 

 nature of the salt absorption process in barley roots, 

 an investigation of their organic acid metabolism was 

 considered useful and Ulrich (1940-41-42) undertook 



Textfigure 36. — Buffer contents of composite 

 expressed saps as influenced by the nature of the 

 salt supplied in the culture solution during solute 

 absorption. The effects of KBr and KHCO3. (From 

 HoAGLAND and Broyer, 1940). 



this. Many factors were studied, but of specific in- 

 terest now are the experiments that showed that the 

 total organic acids of the roots are subject to increases 

 or decreases in concentration in the sap as a result of 

 the unequal intake by the roots of cations or anions. 



From previous discussion, it may be recalled that 

 young roots initially low in potassium can absorb, 



