Physiological mechanisms of Al resistance in higher plants

Aluminum (Al) ion is toxic to plant growth, while the resistance to Al toxicity varies widely among plant species. Accumulating evidence has shown that organic acids play an important role in both internal and external detoxification of Al. Two patterns of Al-induced secretion of organic acid anions have been characterized in the external detoxification. Involvement of ABA or protein phosphorylation in the activation of anion channel in Pattern I and less contribution of organic acid metabolism in Pattern II have been reported. Recently, gene or quantitative trait locus (QTL) for Al-activated secretion of organic acid anions has been identified. Other mechanisms of Al resistance are also reported such as pH increase in the rhizosphere. The formation of a non-toxic Al complex with organic acids or other chelators and sequestering these complexes in the vacuoles play an important role in internal detoxification of Al in Al-accumulating plants.