Short‐term effects of pH and aluminium on mineral nutrition in maize varieties differing in proton and aluminium tolerance

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Abstract
In short‐term (24 h) nutrient solution experiments, the influence of different proton (pH 6.0 and pH 4.3) and aluminium (Al) (0, 20, and 50 μM) concentrations on root and coleoptile elongation, dry weight, and the uptake of selected mineral nutrients was studied in maize (Zea mays L.) varieties that differ in acid soil tolerance under field conditions. The acid‐soil‐tolerant maize varieties, Adour 250 and C525M, proved to be hydrogen (H+) ion sensitive, but Al tolerant, while the acid soil tolerant variety BR201F was H+ tolerant but Al sensitive. The acid soil sensitive variety HS 7777 was affected by both H+ and Al toxicity. The proton‐induced inhibition of root elongation was closely related to the proton‐induced decrease of the specific absorption rates (SAR) of boron (B), iron (Fe), magnesium (Mg), calcium (Ca), and phosphorus (P). In contrast, only the specific absorption rate of B (SARB) was significantly correlated to the Al‐induced inhibition of root elongation. It is concluded, that alterations of nutrient uptake may play an important role in H+ toxicity, while at least after short‐term exposure to Al, alterations of Ca, Fe, Mg, or P uptake do not seem to be responsible for Al‐induced inhibition of root elongation. Further attention deserves the Al‐B interaction, moreover taking into account that a highly significant correlation between Al‐induced increase of callose concentration in root tips and Al‐induced decrease of SARB could be established.