Aluminum is the most abundant metal in the Earth's crust. Although rocks and soils consist of primary and secondary aluminosilicate minerals, the solubility of aluminum in soil solutions is very limited and varies according to soil pH. Trivalent aluminum (Al³⁺) ions predominate in acid soil solutions and may be detrimental to many plant species, especially some widely cultivated crop plants. Therefore, aluminum toxicity is a well-studied topic in agricultural research all over the world. In contrast, relatively little attention has been paid to plants that tolerate very high aluminum concentrations in their shoot tissues.