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Effect of pH in nutrient solution on tolerance to aluminum toxicity in wheat cultivars

The aluminum tolerance of nine wheat cultivars was studied in nutrient solutions using three different levels of pH combined with four different concentrations of this element. The tolerance was evaluated by measuring the root growth in an aluminum-free complete nutrient solution after a previous treatment in aluminum added solutions (0, 5, 10 and 20mg/l) under a particular pH (4.0, 5.0 and 6.0). The wheat cultivars BH-1146, IAC-18, IAC-13 and C-3 presented tolerance, IAC-17 and Alondra-4546 showed moderate tolerance and Siete Cerros, Super-x and CNT-8 were sensitive to the presence of increasing concentrations of Al3+ in the treatment solution under pH 4.0. All cultivars were tolerant to the different concentrations of aluminum under pH 5.0 and 6.0. The aluminum toxicity symptom (inhibition of root growth) was dependent on the pH and the amount of aluminum in the treatment solution. For the same level of aluminum, toxicity symptoms increased, when the pH decreased in the solution from 6.0 to 4.0, considering all the studied cultivars. Apparently wheat tolerance to Al3+ is a relative rather than absolute characteristic, depending on pH among other characteristics.

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