Mitochondria are the site of oxidative phosphorylation in all eukaryotic cells and are the main centres of ATP production. Plant mitochondria have a highly branched ETC that provides flexibility for oxidation of cytosolic and matrix NAD(P)H. In addition to the universal cytochrome pathway found in many organisms, plants have matrix-facing and cytosol-facing non-phosphorylating NAD(P)H dehydrogenases which bypass Complex I and the matrix-facing Alternative oxidase (AOX) which bypasses Complexes III and IV. The alternative pathways are non-proton pumping and allow NAD(P)H oxidation with varying levels of energy conservation and hence this alternative pathway is of particular interest. Recent studies have shown that the alternative respiratory pathways are upregulated during physiological stresses and are suggested to represent adaptive features of plants. The aims of project included creation of transgenic A.thaliana plants with increased levels, by overexpression, and decreased levels, by RNAi, of the cytosol facing non-phosphorylating NAD(P)H dehydrogenase Atndb2 and analysis of the effect of salinity stress on transgenic A.thaliana in which AOX has been knocked out.