Aluminum toxicity in some highly weathered soils of the tropics

The results indicate a nonspecific competition between interfering ions, and Ca, similar to that which occurs for exchange sites on an inert exchanger. On this basis, the reduction in root growth associated with high solution concentrations of Al or other competing ions may be caused by a lack of Ca at the growing root tip. The competitive action of cations such as Al or Ca is not confined to the root tip, but also extend to the ability of the plants to absorb Ca.