Mechanisms of aluminum tolerance in Triticum aestivum (wheat). V. Nitrogen nutrition, plant-induced pH, and tolerance to aluminum; correlation without causality?

An aluminum-tolerant cultivar ('Atlas-66') and an aluminum-sensitive cultivar ('Scout-66') of Triticum aestivum L. were grown in solution culture under conditions of varying [Formula: see text] and [Formula: see text] supply with or without 75 μM aluminum. Plants grown with a low [Formula: see text] ratio in solution maintained a higher solution pH than plants grown with a high [Formula: see text] ratio. Although root growth of 'Scout-66' was greater under high [Formula: see text], high solution pH conditions, the relative tolerance of the cultivars to Al was unaffected by the [Formula: see text] ratio and by solution pH. The superior Al tolerance of 'Atlas-66' could not be explained solely by its ability to maintain a high solution pH in mixed nitrogen solutions.