Possible Path of Entry of Cations into Plant Cells

Abstract

IN a previous publication¹ some data were presented which were interpreted as indicating that Rb⁺ ions move through the plasmalemma of barley root cells on a chain of fixed, negative sites of a macromolecule which probably make up part of a charged pore. The results suggested that this passage of Rb⁺ through the membrane could be slowed down by less mobile ions like Na⁺ or Ca⁺⁺. It was suggested, as a corollary, that if such be the case, the movement of a slow ion on such sites could be accelerated by a fast ion. To test this possibility, absorption rates of sodium-24 in the presence of a fast ion, such as K⁺, were compared with those in the presence of a slower ion like Na⁺.