Hoagland 



— 60 — 



Plant Nutrition 



the roots for some time following excision, while they 

 were immersed in distilled water or in a solution of 

 the relatively inert salt, CaS04. Then in a subsequent 

 period it could be shown that marked increase in the 

 capacity for accumulation of potassium salt resulted 

 from the addition of sugar to the culture medium. 

 Presumably certain growth substances are likewise 

 required although direct proof of this is not easy to 

 obtain under the conditions of these particular experi- 

 ments. On the related processes of exudation to be 



10 



UJ 



z 

 o 



Li. 



o 



UJ 



if) 

 < 



UJ 

 Q. 



>* 



a 



80 



40 



30 



6 12 18 24 30 



TEMPERATURE OF SOLUTION IN DEGREES C 



Textfigure 13. — Showing temperature curve for ab- 

 sorption of potassium by young excised barley roots. 

 Other conditions were all favorable for salt accumulation. 



discussed next time auxin effects were in evidence 

 in the experiments of Skoog, Grossenbacher and 

 Broyer as carried on in Berkeley. It will also be 

 recalled that in the culture of root tips, certain vita- 

 min substances have to be supplied, especially vitamin 

 Bi. In the present experiments it is reasonable to 



