Alternative NADH-ubiquinone oxidoreductase which catalyzes the oxidation of mitochondrial NADH does not translocate protons across the inner mitochondrial membrane (By similarity). NAD(P)H dehydrogenase; more efficient on NADH. a quinone + H(+) + NADH = a quinol + NAD(+) a ubiquinone + H(+) + NADH = a ubiquinol + NAD(+) Binds 1 FAD per subunit. No effect of calcium ions on activity. Optimum pH is 6.8 with NADPH as substrate and 6.8-7.8 with NADH as substrate. Expressed in seedlings, roots, cotyledons, stems, buds and flowers and, to a lower extent, in stems and leaves. Induced by chloramphenicol (Chl), erythromycin (Ery), paraquat (Par), rotenone (Rot) and salicylic acid (SA). Lower reactive oxygen species formation and altered phenotype (e.g. growth rate, root:shoot ratios and leaf area). Lower leaf area early in development followed by a prompt subsequent increase in leaf area leading to larger leaves in mature plants. Better tolerance to salinity stress. These phenotypes are probably due to an enhanced expression of NDB2 and AOX. Belongs to the NADH dehydrogenase family.