File:Absorption and excretion of salts by roots, as influenced by concentration and composition of culture solutions (1912) (16768244112).jpg

Title: Absorption and excretion of salts by roots, as influenced by concentration and composition of culture solutions
Identifier: absorptionexcret231true (find matches)
Year: 1912 (1910s)
Authors: True, Rodney H. (Rodney Howard), 1866-1940; Bartlett, Harley Harris, 1886-1960; United States. Bureau of Plant Industry
Subjects: Roots (Botany); Peas
Publisher: Washington, D. C. : Government Printing Office
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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RECORD OF THE EXPERIMENTS, 35 The plants of this experiment developed very rapidly, and had reached a state of maximum root development after six days. At this time the equilibri- um concentration was 5M about - being 500,000, less than that found for solutions of magne- sium or calcium alone, or for magnesium and calcium in the molec- 9 ular ratio The
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absorption efficiency "was so great that all solutions which at the start were above equi- librium concentration were brought below it before the rate of ex- cretion became greater than the rate of ab- sorption.1 This was not the case in any other experiment. In figure 21 there are three curves. The one which represents the solutions at the end of six days gives the true equilibrium con- centration, for up to that time the roots had been actively growing. The other curves merely indicate the rate at which the salt content of roots which are no longer actively growing passes into the culture solutions. CONCLUSIONS. Our work on the relation of roots to dilute solutions of calcium and magnesium nitrates has thus far shown: (1) That there is a definite i It is obvious that in every culture whose development is limited by lack of light, the entire salt content of the root system must ultimately, as vitality wanes, pass into the culture solution. With peas, the rate of outgo exceeds the rate of intake as soon as root growth stops, long before the roots die or the cotyledons are exhausted. 231 Fig. 21.—Curves showing relation of initial concentration of the cul- ture solutions to subsequent excretion and absorption of salts by pea roots in solutions of Mg(X03)2-rCa(X03)2 in the molecular ratio J.

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