AMERICAN 
JOURNAL OF BOTANY 
Vol. II June, 1915 No. 6 
THE EXCHANGE OF IONS BETWEEN THE ROOTS OF 
LUPINUS ALBUS AND CULTURE SOLUTIONS CON- 
TAINING ONE NUTRIENT SALT^ 
Rodney H. True and Harley Harris Bartlett 
Former work by one of us^ has shown that the roots of Lupinus 
alhus excrete electrolytes when grown in distilled water. From river 
water, on the contrary, the roots actively absorb electrolytes. There 
is a decided difference in root growth in the two cases. As compared 
with river water, the distilled water causes a decided inhibition of 
growth which is doubtless correlated with the loss of necessary salts 
from the roots to the distilled water. When quantities of certain 
calcium or sodium salts equal osmotically to the total salt content of 
Potomac River water are added to distilled water the loss of ions from 
the roots is found to be checked by the presence of calcium salts, but 
not by the presence of the sodium salts. Growth in the calcium solu- 
tions is found to equal that in river water checks; that in NaCl solu- 
tions being only slightly and temporarily better than in distilled water. 
The writers^ have made a study of the concentration relations of dilute 
solutions of calcium and magnesium nitrates to the roots of Pisum 
sativum, and have found that for each of these salts or for a mixture 
of the two, there is a fairly definite concentration at which excretion 
^ Published by permission of the Secretary of Agriculture. 
2 True, Rodney H., The Harmful Action of Distilled Water. Amer. Journ. Bot. 
1:255-274. 1914. 
3 True, R. H., and Bartlett, H. H., Absorption and Excretion of Salts by Roots, 
as Influenced by Concentration and Composition of Culture Solutions. I. Concen- 
tration Relations of Dilute Solutions of Calcium and Magnesium Nitrates to Pea 
Roots. Bulletin 231, Bureau of Plant Industry, U. S. Department of Agriculture, 
Washington, D. C, 1912. 
[The Journal for May (2: 199-254) was issued 16 June 19 15.] 
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