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Abstract: Rye (Secale cereale L.) plants have high tolerance to Al, and become unique tools to study Al-toxicity and tolerance mechanisms. To better understand if and how Al-induced root growth inhibition is related with root histological differentiation, nutrient balances and cell cycle dynamics, tolerant (AT6) and sensitive (AS6) rye lines were exposed for 24h to 1.1mM Al. After that period, half of plants were transferred to medium without Al, while the other group was maintained with Al for more 48h. AS6 plants showed evident and irreversible root growth inhibition, decreases in water content, organic matter and carbohydrate reserves. Also, roots of this line showed greater increases in Ca levels and changes in anatomy (e.g. thickness). Data revealed that AS6 plants accumulate more Al in roots and leaves, suggesting more Al translocation to the shoots. The two lines responded differently to Al exposure in what concerns endodermis differentiation and cell cycle profile. The tolerant line shows a tendency to arrest in G0/G1 phase whereas the sensitive have a tendency to arrest in S phase. These data point to an arrest of cells in specific cell cycle phases, leading to eventual Al-induced cell cycle delay. Taken all together, data show that even short-term exposure to Al leads to root anatomical modifications that in combination with the cell cycle dynamic changes, may represent a plant strategy to cope with this stress. [Copyright &y& Elsevier]