Ion Absorption and Retention by Chlorella pyrenoidosa. III. Selective Accumulation of Rubidium, Potassium and Sodium

Abstract

Summary. The selective preference of Chlorella pyrentoidosa for alkali metal cations was found to have the order Rb>K>>>Na. It was demonstrated that a cation of higher preference can replace in the cell cations of lower preference by an ion interchange process.The replacement of Na from the cell by K or Rb occurred against high external Na concentrations up to 450 meq/l Na.

Potassium and Rubidium Interaction in Their Absorption by Bean Leaf Slices

“…The capability of various plant species to discriminate between K+ and Rb+ varies rather widely (cf Marschner and Schimansky 1971). With proper precautions, especially in the presence of Ca^+ (Pitman 1969), '"'Rb+ can be used as a tracer for K+ absorption in some plant tissues (Epstein et al 1963, Lauchli andEpstein 1970); other plant cells do, however, absorb these two cations at very different rates even in short term experiments (Schaedle and Jacobson 1967, West and Pitman 1967, Jeschke 1970. Differences in the capacity to absorb Rb+ and K *^ are also displayed by different tissues of bean leaf slices (Jacoby 1975a,b); metabolic Rb+ absorption occurred only in the light, was restricted to the guard cells, and seemed not to occur in the mesophyll; K + was however absorbed by mesophyll cells in darkness, and in the light by guard cells as well.…”