Aluminum toxicity in maize: Biomass production and nutrient uptake and translocation

The effect of increasing aluminum (Al) concentrations on root nutrient cont ents along with the concurrent translocation to the shoot of C-4 plants pro mpted this study. Two-week-old maize (Zea mays cv XL-72.3) plants were ther efore submitted for 20 days to Al concentrations ranging from 0 to 3.00 mM in a medium with low ionic strength were used as a test system. Aluminum co ncentrations in root tissues showed a 3-fold increase between 0 and 3.00 mM Al treatment, and was not detected in the shoot. Root plasma membrane-H+ A TPase activity decreased after the 0.33 mg L-1 Al treatment, while membrane permeability increased up to 1.00 mM Al treatment. Root and shoot biomass decreased after the 0.33 mM Al treatment. All elements in the roots, except potassium (K), manganese (Mn), and zinc (Zn) were highest for plants treat ed with 0.33 mM Al. Potassium increased continuously between 0 and 3.00 mM Al treatments, and iron (Fe) decreased above 0.33 mM. Only a slight decreas e in nitrogen (N) was observed. All the measured nutrients in shoots, excep t N, Mn, and Fe decreased above 0.33 mM, but calcium (Ca) and magnesium (Mg ) had little variation as Al varied. Data indicated that maximum net uptake for mineral nutrients, except Mn, occurred up to 0.33 mM Al. Translocation of phosphorus (P), K, Mn, and Zn decreased above 0.33 mM Al, N, and Ca dec reased when any Al was added, and no clear trend was observed for Mg and Fe . Between the 0 and the 3.00 mM Al treatments, electrolytic conductance did not increased significantly indicating that the observed inhibitions of tr anslocation from roots to shoots were not directly related to increasing me mbrane degradation.