Uptake and Transport of Ions in Barley Seedlings II. Evidence for Two Active Stages in Transport to the Shoot

Abstract

For some purposes it is adequate to explain the exudation of salt from roots, and the transport from root to shoot, as the result of a single active transport at the outer surface of the cells of the root. This paper shows that it is also necessary to have a second, active transport prior to entry to the xylem. Support for this model is based on a variety of observations. Tracer uptake interpreted on a symplast model is investigated experimentally and tested by comparison with simulated properties of the system. The effects of CCCP on uptake and transport are related to this model and compared with effects of low salt content on transport and accumulation. The behaviour of excised roots is also compared with the behaviour of whole plants.