Reactive Oxygen Species Production in Wheat Roots Is Not Linked with Changes in H+ Fluxes During Acidic and Aluminium Stresses

Aluminium stress induces peroxidation of lipids in the plasma membrane, the effectakin to that caused by reactive oxygen species (ROS). ROS have recently been proposedas regulators of redox-dependent ion transport across the plasma membrane during bioticand abiotic stresses, thus contributing to the plant defence system. The aim of this studywas to discover whether ROS production is linked to redox-dependent H+ transportsystem located at the plasma membranes of two near-isogenic lines of wheat (Triticumaestivum L., ET8 = Al-resistant, ES8 = Al-sensitive).The activities of NADPH-dependent ROS synthase and SOD were increased in bothwheat lines 15 and 30 min after Al treatments. However, the ROS production was alsoincreased under acidic stress. There was no difference between the two wheat lines in theroot-cell plasma membrane capacity to efflux H+ in response to potassium ferricyanideafter Al and acidic treatments. In ET8, both stresses led to increases in ROS productionand H+ influx.ROS production in wheat seedlings was activated primarily by low pH exposure ratherthan by the Al stress. ROS production and breakdown in wheat seedlings under Al andacidic stresses appear to be linked to the intracellular metabolic changes rather than tothe increased activity of plasma membrane-based NADPH-dependent ROS synthase.