Salt-stress effects on proline concentrations as well as proline metabolizing enzymes activities were studied in durum wheat seedlings. Pro is metabolized in the mitochondria to glutamate via Pro dehydrogenase/oxidase (EC 1.5.99.8) and P5C dehydrogenase (EC 1.5.1.12). We considered mitochondria isolated and purified from durum wheat seedlings to be a suitable experimental system to carry out a specific investigation on the effects of salt stress on mitochondrial function and metabolism. Durum wheat is a species well adapted to the Mediterranean environments, chosen as a model system given that it habitually grows under drought and/or salt stress conditions, where salt stress due to seawater intrusion into aquifers is an increasing problem [Flagella et al; 2006]. Our data provide evidence to support the hypothesis that Pro accumulation in the extramitochondrial phase, is controlled by the mitochondrial permeability (i.e. carrier solely for proline and a proline/glutamate antiporter [De Martino et al; 2006]) rather than by the mitochondrial catabolism. References Flagella et al. Functional Plant Biology 2006 33 (4): 357-366; Di Martino et. al. Planta 2006 May;223(6):1123-33.