Studies on antagonism. II.—The effect of previous immersion of potato tuber tissue in solutions of monovalent, divalent, and trivalent kations on the subsequent absorption of the ammonium ion

Abstract

In the previous of this series (Asprey, 1933) it was suggested that the antagonistic action of a kation towards an accompanying kation depended on two factors; one of these is its competition with the accompanying kation This factor will always tend to reduce the absorption of both ions as compared with that taking place from their pure solutions. The second factor is the specific effect o the ion on the absorptive power of the tissue; this was presumed to differ with the valency of the kation. It was supposed that monovalent kations tend to increase, and divalent, and trivalent kations to decrease, the intake of other kations by the tissue. In the experiments previously described the antagonistic action exhibited by varius kations towards the ammonium ion in its absorption by potato tissue was observed. It was found, however, that only one monovalent salt, lithium chloride, actually increased the ammonium ion in its absorption by potato tissue was observed. It was found, however, that only one monovalent salt, lithium chloride, actually increased the ammonium intake. It was shown that the apparent divergence in the behaviour of lithium and the other monovalent alts could be explained by assuming that the specific effect of all of them on the tissue was the same; to increase the absorption of ammonium, but that the effect of sodium and potassium was very much less than that of lithium. Reduction in absorption caused by ionic competition would then mask the relatively weak tendency of sodium and potassium to increase the intake of ammonium. Although this provided a suitable explanation of the results obtained, there was at that time no evidence either to support or to disprove it. It was decided that some light would be thrown on this matter if experiments could be devised in which the specific effects of salts on the tissue alone were determined. It was thought that by immersing the disks of potato tuber first in solutions of the salts under consideration for a known period and then in ammonium chloride, information might be obtained about the specific effect of these salts on ammonium intake, since ionic competition would be eliminated.