Two experiments were conducted with the objective of studying the tolerance of wheat cultivars to 5 mg/l of Al3+ in nutrient solutions. The tolerance was evaluated by measuring the root growth in an aluminum-free complete nutrient solution after a treatment of 48 hours, in aluminum solution with different levels of phosphorus, and with controlled pH and temperature (25 ± 1ºC). In the first experiment eight cultivars were studied in treatment solutions with four levels of phosphorus (0; 15.5; 31.0 and 62.0 mg/l combined with three levels of pH (4.0; 5.0 and 6.0). The cultivars CNT-8 and Siete Cerros were sensitive and 'BH-1146', 'IAC-18', 'IAC-13', 'C-3', 'IAC-17 and 'Alondra- 4546' were tolerant to 5 mg/l of Al3+ in the solutions with pH 4.0 and in absence of P. All cultivars were sensitive to Al3+ when it was applied 15.5 mg/l of P and they were tolerant when was used 62 mg/l of P in the solutions, considering constant the pH 4.0. In solutions with the level of 31 mg/l of P and pH 4.0, the cultivars IAC-18, BH-1146, IAC-13 and C-3 showed tolerance and IAC-17, Alondra-4546, CNT-8 and Siete Cerros showed sensitivity to Al3+ when it was used solution with pH 5.0 or 6.0 the cultivars presented tolerance being non dependent of P concentration, in consequence of the low activity of Al3+ ions under these pH levels. The data demonstrated that tolerance to 5 m/l of Al3+, besides the pH level was dependent on the P concentration in the solution. The cultivars BH-1146, IAC-17 and Siete Cerros were studied in a second experiment in nutrient solutions with pH 4.0, containing five P concentrations (0; 1.55; 3.875; 7.75 and 15.5 mg/l). 'BH-1146' and 'IAC-17 were tolerant and 'Siete Cerros' was sensitive to 5 mg/l of Al3+ when it was added 0 and 1.55 mg/l of P into the treatment solution. when it was considered the P levels of 3.875; 7.75 and 15.5 mg/l all cultivates showed symptoms of Al toxicity in their mots. There was an increase in P content in aereal part and root dry matter with the increasing amount of P into the solutions, being more evident in 'IAC-17' and 'Siete Cerros' than in 'BH-1146'. Aluminum content in root dry matter increased in all cultivates as the P concentration increased into the solutions, suggesting that Al and P became accumulated in the roots, external or internally.
aluminum x phosphorus interaction; nutrient solutions; tolerance to Al toxicity; sensitivity to Al toxicity; wheat cultivars tolerant to Al; wheat cultivates sensitive to Al