Aluminum (Al) toxicity is a major limiting factor for plant growth on acid soils, where Al is often in a form that can be toxic to plants. While most Al in soils is bound by ligands or in non-toxic forms, solubilization by low pH can release toxic Al. The primary toxic form is Al³⁺, which can enter plant cells and cause damage. The root apex is particularly vulnerable to Al toxicity, as it accumulates more Al and is more susceptible to physical damage. Al can enter the symplasm or interact with the apoplasm, leading to various toxic effects. The exact mechanisms of Al toxicity are still not fully understood, but recent studies suggest that Al can interfere with calcium (Ca) homeostasis, which is crucial for plant metabolism. Al-tolerant plants, such as wheat, have developed mechanisms to exclude Al from the root apex, including the efflux of organic acids like malate, which chelate Al and reduce its toxicity. The Alt1 locus in wheat is associated with this tolerance, and it may code for a channel that facilitates Al-stimulated malate efflux. Other mechanisms include the excretion of citric acid in snapbeans and maize, which also help in detoxifying Al. Al toxicity also induces the synthesis of various proteins in root apices, some of which may play a role in Al tolerance. However, the exact role of these proteins is not yet clear. Future research aims to identify the genes responsible for Al tolerance and understand the biochemical pathways involved. Techniques such as secondary-ion mass spectrometry and patch clamping are being used to study Al uptake and channel activity in plant cells. Understanding these mechanisms is crucial for developing strategies to improve plant growth on acid soils.Aluminum (Al) toxicity is a major limiting factor for plant growth on acid soils, where Al is often in a form that can be toxic to plants. While most Al in soils is bound by ligands or in non-toxic forms, solubilization by low pH can release toxic Al. The primary toxic form is Al³⁺, which can enter plant cells and cause damage. The root apex is particularly vulnerable to Al toxicity, as it accumulates more Al and is more susceptible to physical damage. Al can enter the symplasm or interact with the apoplasm, leading to various toxic effects. The exact mechanisms of Al toxicity are still not fully understood, but recent studies suggest that Al can interfere with calcium (Ca) homeostasis, which is crucial for plant metabolism. Al-tolerant plants, such as wheat, have developed mechanisms to exclude Al from the root apex, including the efflux of organic acids like malate, which chelate Al and reduce its toxicity. The Alt1 locus in wheat is associated with this tolerance, and it may code for a channel that facilitates Al-stimulated malate efflux. Other mechanisms include the excretion of citric acid in snapbeans and maize, which also help in detoxifying Al. Al toxicity also induces the synthesis of various proteins in root apices, some of which may play a role in Al tolerance. However, the exact role of these proteins is not yet clear. Future research aims to identify the genes responsible for Al tolerance and understand the biochemical pathways involved. Techniques such as secondary-ion mass spectrometry and patch clamping are being used to study Al uptake and channel activity in plant cells. Understanding these mechanisms is crucial for developing strategies to improve plant growth on acid soils.