Summary
The dependence of individual ion fluxes at the plasmalemma and at the tonoplast and of the amounts of ions in the cytoplasmic and vacuolar phases on external concentration was investigated using the method outlined by Pitman (1963). The results are compared with ion uptake isotherms from the literature. It is concluded that flux from the solution into the cytoplasm corresponds to system 1 and flux from the cytoplasm to the vacuole is congruent with system 2. The hypothesis of Torii and Laties (1966a) regarding the location of system 1 and system 2 within the cell is thus reemphazised. The changes of the amounts of internal ions with external concentration clearly demonstrate that the plasmalemma loses its function as a barrier at concentrations above 1 mM. The conclusions which can be drawn from investigations of isotherm kinetics and flux analysis are examined.
Zusammenfassung
Mit Hilfe der von Pitman (1963) beschriebenen Methode wurde die Abhängigkeit der einzelnen Ionenfluxe am Plasmalemma und am Tonoplasten und des Ionengehaltes im Plasma und in der Vacuole von der Außenkonzentration untersucht. Die erhaltenen Kurven wurden mit Ionenaufnahmeisothermen aus der Literatur verglichen. Dabei zeigte sich, daß der Flux aus der Außenlösung in das Cytoplasma dem sogenannten System 1 und der Flux aus dem Cytoplasma in die Vacuole dem System 2 der Isothermenkinetik entspricht. Dies ist ein weiterer Beleg für die Richtigkeit der Theorie von Torii und Laties (1966a) über die Lokalisierung von System 1 und System 2 innerhalb der Zelle. Die Veränderung der im Cytoplasma und in der Vacuole enthaltenen Ionenmenge mit steigender Außenkonzentration läßt deutlich werden, daß das Plasmalemma seine Barrierenfunktion bei Konzentrationen über 1 mM verliert. Es wird diskutiert, welche Aussagen über Transportprozesse mit den beiden Methoden der Isothermenkinetik und der Effluxanalyse gemacht werden können.
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Lüttge, U., Bauer, K. Evaluation of ion uptake isotherms and analysis of individual fluxes of ions. Planta 80, 52–64 (1968). https://doi.org/10.1007/BF00387189
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DOI: https://doi.org/10.1007/BF00387189