AMERICAN 
JOURNAL OF BOTANY 
Vol. II July, 1915 No. 7 
THE EXCHANGE OF IONS BETWEEN THE ROOTS OF 
LUPINUS ALBUS AND CULTURE SOLUTIONS 
CONTAINING TWO NUTRIENT SALTS^ 
Rodney H. True and Harley Harris Bartlett 
It has been shown by the authors in a former paper^ that in un- 
mixed dilute solutions of the common nutrient salts seedlings of 
Lupinus alb'us respond differently to different salts with respect to 
absorption. Calcium salts are absorbed from solutions of all dilutions 
tested, as indicated by the clearly marked decrease in the electrical 
conductivity of these solutions during the life of the seedlings grown 
in them. Magnesium salts are absorbed in a slight degree and only 
from solutions of a markedly limited range of concentration. Potas- 
sium salts either behave like distilled water and cause a loss of electro- 
lytes at all dilutions, as in the cases of KH2PO4 and KCl, or permit 
only a minimal absorption phase to come to expression in the more 
favorable concentrations, as in solutions of K2SO4 and KNO3. It 
seems that a predominating influence is exerted by the kations; 
calcium, magnesium or potassium action being clearly marked what- 
ever the accompanying anion may be. The anions, however, are not 
without significance in relation to absorption. 
In this investigation the same test plant, Lupinus albus L., was 
exposed to solutions containing mixtures of the nitrates of Ca, Mg and 
K in pairs in different proportions and in different total concentrations. 
The more concentrated members of the series approached in total salt 
content the soil solution as it is likely to be found in the vicinity of 
^ Published by permission of the Secretary of Agriculture. 
2 True, R. H., and Bartlett, H. H. The exchange of ions between the roots of 
Lupinus albus and culture solutions containing one nutrient salt. Amer. Journ. 
Bot. 2: 255-278. 1915. 
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