o 



AGRICULTURAL 

 LIBRARY, 



imiVERSITY 



— —OF 



Reprinted from the Botanical Gazette 45: 117-124, Febniar 1908 



CALTFOPNVV 



Main lib. 



THE ANTAGONISTIC ACTION OF MAGNESIUM AND 



POTASSIUM 



W. J. V. OSTERHOITT 



(with three figures) 



It has been previously pointed out^ that potassium may inhibit 

 more or less fully the poisonous effects of magnesium and that the 

 abundance of potassium in the soil makes this inhibitory action of 

 importance in soil investigations. Loew and Aso^ have criticized 

 this statement. Their objections are that only chlorids were used 

 and that no flowering plants were investigated. In the present paper 

 these objections are fully met. The experiments extend over a wide 

 range of iforms and their general agreement furnishes conclusive proof 

 of the above-mentioned action of potassium. 



The technique employed has already been described in previous 

 papers in this journal.^ The material was placed in glass dishes con- 

 taining 100-300^'= of the solution and was covered with glass plates to 

 exclude dust and hinder evaporation. Water twice distilled and salts 

 which were tested for purity were used throughout. The results given 

 in the tables are in all cases averages of several series of experiments. 



The first experiments were made upon a marine alga, Entero- 

 morpha Hopkirkii, which is able to live in both sea water and dis- 

 tilled water. It was taken from the sea water, rinsed in distilled 

 water, and placed directly in the solutions. The solutions used were 

 of the concentration 0.37 5 w, which has the same osmotic pressure 

 as the sea water in which the plants naturally grow. 



In pure MgCl^ .0375 w they lived but four days; in pure KCl .0375 w 

 seven days; while in distilled water and sea water they were alive 

 and vigorous at the end of twenty days when the experiment was dis- 

 continued. It is evident therefore that both KCl and MgCl^ have a 

 poisonous action. 



This poisonous effect largely disappears if we mix the two salts 



I OsTERHouT, University of California Publications, Botany 2:235. 1906. 

 ' Loew and Aso, Bull. Imp. Coll. Agr. Tokyo 7:395. 1907. 



3 OSTERHOUT, BOT. GAZETTE 42:127-134. 1906; 44:259-272. I907. 



117] [Botanical Gazette, vol. 45 



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