The aluminium response network in perennial ryegrass (Lolium perenne): II. Water fluxes and ion transport

Abstract

Aluminium toxicity was investigated by analyzing the mineral nutrition and water-use characteristics of hydroponically-grown plants differing in tolerance to Al when subjected to Al (0, 20, 40, 80 μM: pH 4.5) for 28 days. Both lines reacted to Al by increasing their water-use. The Al-tolerant plants were, however, able to control the Al-stimulated water fluxes and progressive increases in water-use (increasing Al) were limited to the Al-sensitive material. Although Al was not generally transported into the foliage, Al treatments nevertheless elicited changes in the composition of the leaves including apparently opposite effects on the Ca, K and P levels found in Al- tolerant and Al-sensitive plants. Analysis of these differences revealed that leaf Ca concentrations were positively related to water-use while leaf K was antagonistically linked to Ca and thus inversely related to the Al- stimulated changes in the plants' water-use. Differences in K nutrition centred around P transport and fluctuations in leaf P paralleled the Al-stimulated changes in foliar K concentrations. These findings are used to develop a theory of root-to-shoot communication in Al-stressed plants which encompasses water fluxes and ion transport processes.