Lecture 6, 



SOME BIOCHEMICAL PROBLEMS ASSOCIATED 

 WITH SALT ABSORPTION 



Whenever salt is accumulated or actively trans- 

 ported by living cells, their metabolism is inevitably 

 involved. An understanding of the mechanisms that 

 result in salt movement (or the active movement of 

 other solutes) must ultimately be found largely in 

 the realm of biochemistry. It is the purpose of the 

 present discussion to summarize several aspects of 

 the problems of chemical processes occurring in plant 

 tissues as salt is moving into or through the cells, or 

 soon after the salt has been accumulated. 



There is need at once for recognizing a difficulty 

 in the interpretation of biochemical observations in 

 terms of certain views on salt accumulation discussed 

 in recent literature. That is, to decide whether or not 

 a metabolic reaction taking place concomitantly with 

 the entrance of salt into the cell has any causal rela- 

 tionship to the continued accumulation of the salt. 

 For example, in roots and storage tissues (as repre- 

 sented by the potato tuber) , the accumulation of potas- 

 sium salt is usually accompanied by an increase in CO2 

 production, with tissues placed in distilled water as 

 a basis for comparison. One possible type of assump- 

 tion is that a small amount of potassium or other ions 

 first enters the protoplasm and stimulates metabolic 

 reactions that lead to liberation of cellular energy 

 available for the accumulation of salt against a po- 

 tential gradient. On the other hand, the increase of 

 CO2 production could be merely the effect on metabol- 



