A Common Feature of the Uptake of Solutes by Root Parenchyma Cells

Abstract

After carrot root tissue has accumulated KCl for 4 days or more, the internal KCl concentration rises from 10 to over 100 µmol g^-1. In the KCl-loaded state, the influxes of a range of solutes are reduced by up to 90%. These solutes are the anions Cl^-, NO₃^-, ClO₃^-, H₂PO₄^-, benzenesulfonate, and malate; the cation K⁺ ; and the neutral molecules glucose and urea. The influx of mannitol is not affected, The fall in influx with KCl loading is not due to increased turgor or decreased sugar concentration in the tissue.

The question of what feature the various transport systems share in common is discussed. A common signal is thought to be more likely than a common mechanism of transport. The main implication of the findings is that the system regulating the accumulation of Cl^- (which was recognized in earlier work) must in fact be only a part of a more complex regulatory system which operates naturally, in vivo, on a range of solutes, but whose significance is not yet otherwise understood.