ELECTEOLYTIC DETERMINATION OF EXOSMOSIS 

 FROM THE ROOTS OF PLANTS SUBJECTED TO 



THE ACTION OF VARIOUS AGENTS 



M. C. MERRILL 



Formerly Research Assistant to the Missouri Botanical Garden 



I. Introduction 



In a previous paper the writer ('15) gave some results 

 showing the exosmosis curves when normal growing plants 

 are taken from a full nutrient medium and placed in redis- 

 tilled water. Those results and the data herewith given show 

 that exosmosis of electrolytes is a constant feature associated 

 with the transfer of normal growing plants from a full nutri- 

 ent solution to distilled water. In the paper above mentioned 

 evidence was introduced indicating that such exosmosis was 

 not a causal injury but that it was simply a concomitant con- 

 dition or incidental effect and had but an indirect relation to 

 the inimical condition of the plant in the distilled water. For 

 convenience we might designate the agency or agencies caus- 

 ing such exosmosis as passive in their effects. 



In this paper are given results on exosmosis in terms of the 

 electrolytic conductivity of the medium when such excretion 

 is caused, or at least is accelerated, by various factors or agen- 

 cies which we may designate as active in their effects. Accord- 

 ingly, plants have been treated by injurious agents or subjected 

 to conditions of different kinds and the comparative effects 

 on the exosmosis from the roots have been noted. By determin- 

 ing the conductivity of the medium at various intervals sub- 

 sequent to the treatment, data have been secured for plotting 

 the exosmosis curves shown in this paper. It has also been 

 the aim to determine in each case the approximate boundary 

 between the normal and the abnormal exosmosis by varying 

 either the duration of application or the concentration of the 

 substance applied, or both. Hence in most cases there will 

 be found the two extremes with any given substance — at the 

 upper end of the scale the curve of excessive exosmosis due to 



Ann. Mo. Bot. Gard., Vol. 2, 1915 



(507) 



