Lecture 7 — 171 — Potassium Nutrition 



tion of potassium by potato tuber discs. Possibly this 

 function of potassium is of primary importance in 

 the synthesis of various kinds of proteins formed by 

 meristematic cells. Certainly potassium accumulates 

 rapidly at growing points, and readily migrates from 

 older tissues to meristematic regions. 



Conclusions about the possible direct or near-direct 

 function of potassium in protein synthesis will vary 

 depending on the kind of experiments from which 

 conclusions are drawn. The stage of plant growth, 

 the interactions of nutrients, and degrees of potassium 

 deficiency all complicate the issue. Statistical correla- 

 tion of factors may provide illumination, but the use 

 of this tool cannot elucidate the actual mechanism by 

 which potassium operates in the plant. 



With regard to the condensation of sugar units to 

 form starch or other polysaccharides there is lacking 

 sufficient proof that potassium is immediately essential 

 for these processes, while phosphate has been shown 

 to be necessary for the in vitro synthesis of starch. 

 In some experiments potassium deficient plants have 

 been observed to be readily capable of starch forma- 

 tion or digestion. 



Some of these views might seem to be contradicted 

 by studies here and elsewhere in which barley plants 

 have been grown throughout their cycle in potassium 

 deficient soils. The result then is that the total carbo- 

 hydrate content of the plant is decreased, and the 

 grain is shrunken in comparison with that of plants 

 receiving a full supply of potassium. There is no 

 necessary inconsistency in the observations from the 

 two types of experiments. When plants are grown 

 for a long period under potassium deficiency, carbo- 

 hydrate synthesis and metabolism will be affected, no 

 matter what the essential function of potassium may 



be. 



There is no disproof of the assumption that potas- 

 sium may be more or less directly essential to the 

 photosynthetic process. In our young low-potassium 



