174 Plant Physiology 



tions is not due to the presence of K compounds, and this 

 fact has been abundantly demonstrated. 



With this osmotic relation in view, it was natural that 

 there should exist also the belief that plants afforded an 

 abundance of potash are better able to withstand drought. 

 This is not yet sufficiently proven. Resistance to drought 

 may possibly be due in part merely to increased salt con- 

 tent of the plant ; in which case, however, it would be 

 inferred that many soluble salts should have a similar 

 effect. The latter is not reported to be the case. The 

 experiments of Atkinson in Alabama on the prevention 

 of " rust " of cotton have been interpreted to mean that 

 potassic fertilizers are partially important in the water 

 relation of the plant, guaranteeing sufficient water, con- 

 sequently preventing the blight, which is a combination 

 of drought and fungous effects. Nevertheless, there is 

 apparently no evidence that desert plants possess any 

 particular relation to potassium. It is also claimed that 

 by virtue of relations to the water-content plants well 

 supplied with potash would be less injured by freezing. 



Maturity, quality, and color. - The belief is current 

 that orchard trees well fertilized with potash ripen their 

 wood more thoroughly, and that as a partial but direct 

 consequence of this the shoots and buds are not so subject 

 to winter or early spring injury. In other words, the belief 

 indicates that potash content is a special factor in the har- 

 diness of perennials. Heightened color and quality in 

 apples has also been attributed to it, but a careful exami- 

 nation of this point indicates that there is no such relation. 

 It seems rather that such a deficiency of any element as 

 to check growth necessarily affects quality. 



