Long-term effects of aluminum exposure on nutrient uptake by maize genotypes differing in aluminum resistance

Genotypic differences in resistance to aluminum (Al) found in many plant species grown in conditions of Al stress seem to include differences in Al-induced inhibition of absorption and utilization of nutrients. Aiming to study the Al effects on nutrient uptake of maize genotypes differing in Al resistance and to check whether differences in mineral nutrition under Al stress correspond with resistance to Al in maize, an experiment involving 10 maize genotypes differing in Al resistance and 2 concentrations of At (0 and 100 muM Al) was established. Total plant (shoot + root) uptake of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) was determined in maize plants after 14 days of growth in culture solution at the two concentrations of Al. The relative uptake [(uptake at 100 muM Al/uptake at 0 muM Al) x 100] of the nutrients studied varied from 22% to 157%, indicating the existence of intraspecific variation for such feature in the presence of Al. Generally, Al had negative effects on the uptake of macro- and micronutrients. At effects were most pronounced on the uptake of Ca and Mg, with respective reductions of 61% and 72%, when averaged across the 10 genotypes. Among the micronutrients, the most pronounced effects of Al were noted on Mn and Zn. Despite showing significant reductions in uptake of Ca and Mg, the maize genotypes showed a rather variable sensitivity to the Al stress imposed, which was related to their general resistance to Al previously assessed using root length as indicator. Under conditions of Al stress, genotypes more resistant to Al maintained a relatively higher absorption of both Ca and Mg than those more sensitive to Al, suggesting that the ability of a genotype to maintain a less disturbed nutrient uptake under Al stress can be an important component in resistance to Al.