Chemical analysis of plant fractions of maize cultivars TX 24 and HL 1 grown in liquid culture containing Al showed that the action of Al was directed at the uptake of Ca and Mg and the transport of P and K. Highly significant cultivar differences in the pattern of Al uptake, notably at low solution Al concentrations were identified. P transport between roots and shoots diminished with increased root Al concentrations. An Al-induced decline in root metabolism was found to occur in intact roots (20 h) and cultivar differences in the ability to maintain root respiration in the presence of Al coincided with cultivar differences in P transport. In the absence of Al, both cultivars responded to low Mg levels by taking up correspondingly more Ca and K without significantly affecting yield. It is therefore suggested that a major requirement for these ions involves charge neutralization. Furthermore, since the root Mg concentrations recorded in these experiments were comparable to those found in plants showing a high degree of Al injury, it was also concluded that these Mg levels were adequate to meet specific functional requirements for this element in the plant. A hypothesis was developed which involved interference by Al in root metabolism which depressed active ion movement and thereby lowered the cation retention capacity of the root. This concept accorded with the linear relationships observed between leaf P and root concentrations of Ca and Mg found in Al-stressed plants.S. Afr. J. Plant Soil1986, 3: 11–17