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An Appraisal of the dai/dx Hypothesis
Author(s) -
Olsen R. A.
Publication year - 1969
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1969.03615995003300060027x
Subject(s) - absorption (acoustics) , absorption rate , chemistry , ion , mathematics , chromatography , physics , optics , organic chemistry
An attempt was made to subject the da i /dx hypothesis to a more critical experimental appraisal than has been accomplished previously. A system was devised by the use of synthetic exchanger particles in which the suspension effect, as measured electrometrically, was exceptionally large; the value indicated an apparent difference in a Rb + in the most extreme parts of the system of about one million. According to the da i /dx hypothesis, the rate of absorption of Rb + by plant roots should have differed from these two parts of the system by a correspondingly large factor. The observed rates of absorption from all parts of the system, however, were within a factor of 1.2 of being identical. It is concluded that either: (i) electrometric methods do not provide a reliable estimation of ion activities in aqueous systems containing exchanger particles, (ii) the rate of absorption of an ion by plant roots is not a function of the activity gradient extending normal to the absorption surface, or (iii) both of these commonly accepted postulates are incorrect. The data are considered to be consistent with the alternative dμ̄ i /dx hypothesis.