Kinetic Studies of Anion Absorption by Potato Slices at 0 C

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Abstract
The time course of chloride, bromide, and phosphate uptake at 0[degree]C by potato disks transferred from 25[degree]C follows a 2-component absorption pattern [long dash]an initial period of rapid uptake (the absorption shoulder) followed by a period of steady-state uptake. The absorption shoulder is shown to be specific for a given ion or ionic species. Bromide and chloride compete with one another for the shoulder, and nitrate interferes with halide uptake. Sulfate does not compete with halide nor does phosphate with chloride or vice versa. The shoulder is clearly a property of the living cell being wiped out by pretreatment at 0[degree]C or by 2,4-dinitrophenol. It is suggested that the shoulder may reflect the filling of absorption sites in the cytoplasm while the steady state is indicative of vacuolar penetration.