Allosteric and Non‐Allosteric Regulation of Rubidium Influx in Barley Roots

Abstract

Abstract Uptake of Rb + was investigated in 6–8‐day‐old intact barley plants ( Hordeum vulgare cv. Kristina), which had been cultivated or pretreated in nutrient solutions with various K + concentrations. The relationship between Rb + influx and the K + concentration of roots appeared to be sigmoidal for plants grown in solutions containing K + , indicating regulation of Rb + uptake by allosteric inhibition of the uptake mechanism. Pretreatment of the roots in K + ‐free solutions changed the pattern of uptake and caused the Rb + influx to become linearly related to the chemical Rb + potential of the uptake solution. Pretreatment in K + ‐free solutions probably abolishes the allosteric inhibition of a carrier system.