Organic acids reduce aluminum toxicity in maize root membranes

Abstract

Application of 10–50 μ M Al ions to a plasma membrane‐enriched microsomal fraction, isolated from roots of maize ( Zea mays L.), resulted in decreased Mg 2 ‐ATPase activity. This was probably caused by changes in membrane structure as detected by the use of spin probes. Both enzymatic activity and membrane structure could in part be protected from Al injury when organic acids, similar to those found in maize root tissue, were administered prior to the metal. When stressed by application of Al ions, the Al‐tolerant maize hybrid, W64, maintained higher concentrations of organic acids, especially malic and trans ‐aconitic, than the Al‐sensitive maize hybrid, A632. We hypothesize that citric and malic acid, because of their high stability constants with Al and/or the acid's concentration reduce Al toxicity in maize root tissue, especially in the Al‐tolerant line.