A System for Measuring the Uptake of Ions by Plants from Flowing Solutions of Controlled Composition

Abstract

A system is described for growing plants in flowing solution in which the concentration (activity) of some nutrient ions is continuously monitored and held almost constant by means of ion-selective electrodes which control the operation of nutrient pumps. By recording the concentration of a given ion in the flowing nutrient solution and the amount of that ion which is delivered by the nutrient pumps, it is possible to follow nutrient uptake over long and short periods. A brief account is given of the operation of the system using a nitrate ion-selective electrode to examine aspects of $NO3−$ uptake by perennial ryegrass (Lolium perenne L.).